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1. Small‐Scale Magnetic Structures: Cluster Observations

Author: Michael Gedalin, Michael A. Balikhin, P. Canu, Simon Walker, Keith H. Yearby, Department of Automatic Control and Systems Engineering [ Sheffield] (ACSE), University of Sheffield [Sheffield], Department of Automatic Control and Systems Engineering, Department of Physics [Beer-Sheva], Ben-Gurion University of the Negev (BGU), Laboratoire de Physique des Plasmas (LPP), Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Sorbonne Université (SU)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
Subjects: Physics, Geophysics, 010504 meteorology & atmospheric sciences, Scale (ratio), Space and Planetary Science, 0103 physical sciences, Cluster (physics), [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Statistical physics, 010303 astronomy & astrophysics, 01 natural sciences, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences
Abstract: International audience
Published: 2021
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2. Cluster observations of ELF/VLF signals generated by modulated heating of the lower ionosphere with the HAARP HF transmitter

Author: Timothy F. Bell, Jean-Gabriel Trotignon, Umran S. Inan, Jean-Louis Rauch, P. Canu, E. J. Kennedy, M. Platino, Jolene S. Pickett, Space, Telecommunications, and Radioscience Laboratory (STAR Lab), Stanford University, Department of Physics and Astronomy [Iowa City], University of Iowa [Iowa City], Naval Research Laboratory (NRL), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Centre d'étude des environnements terrestre et planétaires (CETP), and Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Atmospheric Science, 010504 meteorology & atmospheric sciences, Field line, Magnetosphere, Electrojet, 01 natural sciences, [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), lcsh:Science, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Physics, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], lcsh:QC801-809, Transmitter, Geology, Astronomy and Astrophysics, Geophysics, lcsh:QC1-999, lcsh:Geophysics. Cosmic physics, Amplitude, Space and Planetary Science, lcsh:Q, Satellite, Ionosphere, lcsh:Physics, Radio wave
Abstract: It is now well known that amplitude modulated HF transmissions into the ionosphere can be used to generate ELF/VLF signals using the so-called "electrojet antenna". Although most observations of the generated ELF/VLF signals have been made on the ground, several low and high-altitude satellite observations have also been reported (James et al., 1990). One of the important unknowns in the physics of ELF/VLF wave generation by ionospheric heating is the volume of the magnetosphere illuminated by the ELF/VLF waves. In an attempt to investigate this question further, ground-satellite conjunction experiments have recently been conducted using the four Cluster satellites and the HF heater of the High-Frequency Active Auroral Research Program (HAARP) facility in Gakona, Alaska. Being located on largely closed field lines at L≈4.9, HAARP is currently also being used for ground-to-ground type of ELF/VLF wave-injection experiments, and will be increasingly used for this purpose as it is now being upgraded for higher power operation. In this paper, we describe the HAARP installation and present recent results of the HAARP-Cluster experiments. We give an overview of the detected ELF/VLF signals at Cluster, and a possible explanation of the spectral signature detected, as well as the determination of the location of the point of injection of the HAARP ELF/VLF signals into the magnetosphere using ray tracing.
Published: 2018
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3. Remote sensing of a NTC radio source from a Cluster tilted spacecraft pair

Author: S. Rochel Grimald, Jean-Gabriel Trotignon, X. Vallières, Fabien Darrouzet, Jean-Louis Rauch, F. El-Lemdani Mazouz, G. Lointier, P. Canu, S. Kougblénou, P. M. E. Décréau, Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Laboratoire de Physique des Plasmas (LPP), Université Paris-Sud - Paris 11 (UP11)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Sorbonne Université (SU)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'étude des microstructures [Châtillon] (LEM - ONERA - CNRS), Centre National de la Recherche Scientifique (CNRS)-ONERA, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique (BIRA-IASB), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), ONERA - The French Aerospace Lab [Châtillon], ONERA-Université Paris Saclay (COmUE), HELIOS - LATMOS, Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and ONERA-Centre National de la Recherche Scientifique (CNRS)
Subjects: Atmospheric Science, [PHYS.ASTR.IM]Physics [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], 010504 meteorology & atmospheric sciences, Plane wave, 01 natural sciences, Directivity, Optics, Electric field, 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), Geomagnetic latitude, lcsh:Science, 010303 astronomy & astrophysics, Circular polarization, 0105 earth and related environmental sciences, Remote sensing, Physics, [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], Spacecraft, business.industry, lcsh:QC801-809, Geology, Astronomy and Astrophysics, Polarization (waves), lcsh:QC1-999, [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], lcsh:Geophysics. Cosmic physics, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Physics::Space Physics, lcsh:Q, Astrophysics::Earth and Planetary Astrophysics, business, lcsh:Physics, Radio wave
Abstract: The Cluster mission operated a "tilt campaign" during the month of May 2008. Two of the four identical Cluster spacecraft were placed at a close distance (~50 km) from each other and the spin axis of one of the spacecraft pair was tilted by an angle of ~46°. This gave the opportunity, for the first time in space, to measure global characteristics of AC electric field, at the sensitivity available with long boom (88 m) antennas, simultaneously from the specific configuration of the tilted pair of satellites and from the available base of three satellites placed at a large characteristic separation (~1 RE). This paper describes how global characteristics of radio waves, in this case the configuration of the electric field polarization ellipse in 3-D-space, are identified from in situ measurements of spin modulation features by the tilted pair, validating a novel experimental concept. In the event selected for analysis, non-thermal continuum (NTC) waves in the 15–25 kHz frequency range are observed from the Cluster constellation placed above the polar cap. The observed intensity variations with spin angle are those of plane waves, with an electric field polarization close to circular, at an ellipticity ratio e = 0.87. We derive the source position in 3-D by two different methods. The first one uses ray path orientation (measured by the tilted pair) combined with spectral signature of magnetic field magnitude at source. The second one is obtained via triangulation from the three spacecraft baseline, using estimation of directivity angles under assumption of circular polarization. The two results are not compatible, placing sources widely apart. We present a general study of the level of systematic errors due to the assumption of circular polarization, linked to the second approach, and show how this approach can lead to poor triangulation and wrong source positioning. The estimation derived from the first method places the NTC source region in the dawn sector, at a large L value (L ~ 10) and a medium geomagnetic latitude (35° S). We discuss these untypical results within the frame of the geophysical conditions prevailing that day, i.e. a particularly quiet long time interval, followed by a short increase of magnetic activity.
Published: 2018
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4. Wide-banded NTC radiation: local to remote observations by the four Cluster satellites

Author: I. Galkina, Fabien Darrouzet, P. Canu, A. Denazelle, P. M. E. Décréau, Jean-Louis Rauch, S. Rochel Grimald, F. El-Lemdani Mazouz, S. Aoutou, X. Vallières, Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Laboratoire de Physique des Plasmas (LPP), Université Paris-Sud - Paris 11 (UP11)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Sorbonne Université (SU)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), ONERA / DPHY, Université de Toulouse [Toulouse], ONERA-PRES Université de Toulouse, HELIOS - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique (BIRA-IASB), Université Paris-Saclay-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11)-École polytechnique (X)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)
Subjects: Atmospheric Science, 010504 meteorology & atmospheric sciences, Plasmasphere, Plasma oscillation, 01 natural sciences, Electromagnetic radiation, Earth radius, Spectral line, Optics, [PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], Electric field, 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), lcsh:Science, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Physics, business.industry, lcsh:QC801-809, Geology, Astronomy and Astrophysics, lcsh:QC1-999, [PHYS.PHYS.PHYS-SPACE-PH]Physics [physics]/Physics [physics]/Space Physics [physics.space-ph], Computational physics, lcsh:Geophysics. Cosmic physics, Space and Planetary Science, lcsh:Q, Satellite, business, lcsh:Physics, Radio wave
Abstract: The Cluster multi-point mission offers a unique collection of non-thermal continuum (NTC) radio waves observed in the 2–80 kHz frequency range over almost 15 years, from various view points over the radiating plasmasphere. Here we present rather infrequent case events, such as when primary electrostatic sources of such waves are embedded within the plasmapause boundary far from the magnetic equatorial plane. The spectral signature of the emitted electromagnetic waves is structured as a series of wide harmonic bands within the range covered by the step in plasma frequency encountered at the boundary. Developing the concept that the frequency distance df between harmonic bands measures the magnetic field magnitude B at the source (df = Fce, electron gyrofrequency), we analyse three selected events. The first one (studied in Grimald et al., 2008) presents electric field signatures observed by a Cluster constellation of small size (~ 200 to 1000 km spacecraft separation) placed in the vicinity of sources. The electric field frequency spectra display frequency peaks placed at frequencies fs = n df (n being an integer), with df of the order of Fce values encountered at the plasmapause by the spacecraft. The second event, taken from the Cluster tilt campaign, leads to a 3-D view of NTC waves ray path orientations and to a localization of a global source region at several Earth radii (RE) from Cluster (Décréau et al., 2013). The measured spectra present successive peaks placed at fs ~ (n+ 1/2) df. Next, considering if both situations might be two facets of the same phenomenon, we analyze a third event. The Cluster fleet, configured into a constellation of large size (~ 8000 to 25 000 km spacecraft separation), allows us to observe wide-banded NTC waves at different distances from their sources. Two new findings can be derived from our analysis. First, we point out that a large portion of the plasmasphere boundary layer, covering a large range of magnetic latitudes, is radiating radio waves. The radio waves are issued from multiple sources of small size, each related to a given fs series and radiating inside a beam of narrow cone angle, referred to as a beamlet. The beamlets illuminate different satellites simultaneously, at different characteristic fs values, according to the latitude at which the satellite is placed. Second, when an observing satellite moves away from its assumed source region (the plasmapause surface), it is illuminated by several beamlets, issued from nearby sources with characteristic fs values close to each other. The addition of radio waves blurs the spectra of the overall received electric field. It can move the signal peaks such that their position fs satisfiesfs = (n+α) df, with 0 < α < 1. These findings open new perspectives for the interpretation of NTC events displaying harmonic signatures.
Published: 2015
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5. Lower hybrid resonances stimulated by the four CLUSTER relaxation sounders deep inside the plasmasphere: observations and inferred plasma characteristics

Author: P. Canu, Xavier Vallières, Arnaud Masson, Jolene S. Pickett, S. Kougblénou, Jean-Gabriel Trotignon, G. Lointier, Jean-Louis Rauch, Pierrette Décréau, Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Laboratoire de Physique des Plasmas (LPP), Université Paris-Sud - Paris 11 (UP11)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Sorbonne Université (SU)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Research and Scientific Support Department, ESTEC (RSSD), European Space Research and Technology Centre (ESTEC), European Space Agency (ESA)-European Space Agency (ESA), Department of Physics and Astronomy [Ames, Iowa], Iowa State University (ISU), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Agence Spatiale Européenne = European Space Agency (ESA)-Agence Spatiale Européenne = European Space Agency (ESA)
Subjects: Atmospheric Science, Electron density, 010504 meteorology & atmospheric sciences, Plasmasphere, Plasma oscillation, 01 natural sciences, Spectral line, Effective mass (solid-state physics), 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), lcsh:Science, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Physics, lcsh:QC801-809, Geology, Astronomy and Astrophysics, Plasma, Geophysics, Lower hybrid oscillation, lcsh:QC1-999, Computational physics, lcsh:Geophysics. Cosmic physics, Earth's magnetic field, Space and Planetary Science, [SDU]Sciences of the Universe [physics], lcsh:Q, lcsh:Physics
Abstract: The frequency range of the WHISPER relaxation sounder instrument on board CLUSTER, 4–80 kHz, has been chosen so as to encompass the electron gyro-frequency, Fce, and the electron plasma frequency, Fp, in most regions to be explored. Measurement of those frequencies, which are triggered as resonances by the sounder, provides a direct estimation of in situ fundamental plasma characteristics: electron density and magnetic field intensity. In the late mission phase, CLUSTER penetrated regions deep inside the plasmasphere where Fce and Fp are much higher than the upper frequency of the sounder's range. However, they are of the right order of magnitude as to place the lower hybrid frequency, Flh, in the 4–15 kHz band. This characteristic frequency, placed at a resonance of the medium, is triggered by the sounder's transmitter and shows up as an isolated peak in the received spectrum, not present in spectra of naturally occuring VLF waves. This paper illustrates, from analysis of case events, how measured Flh values give access to a plasma diagnostic novel of its kind. CLUSTER, travelling along its orbit, encounters favourable conditions where Fce is increasing and Fp decreasing, such that Fce/Fp increases from values below unity to values above unity. Measured Flh values thus give access, in turn, to the effective mass, Meff, indicative of plasma ion composition, and to the core plasmasphere electron density value, a parameter difficult to measure. The analysed case events indicate that the estimated quantities (Meff in the 1.0–1.4 range, Ne in the 5 × 102–104 cm−3 range) are varying with external factors (altitude, L value, geomagnetic activity) in a plausible way. Although covering only a restricted region (mid-latitude, low altitude inner plasmasphere), these measurements are available, since late 2009, for all CLUSTER perigee passes not affected by eclipses (on average, roughly a third of a total of ~200 passes per year) and offer multipoint observations previously unavailable in this region.
Published: 2011
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6. Titan's ionosphere in the magnetosheath: Cassini RPWS results during the T32 flyby

Author: Stamatios M. Krimigis, K. Ågren, Ronan Modolo, Nick Sergis, J. H. Waite, M. K. Dougherty, D. A. Gurnett, Lisa Rosenqvist, Mats André, P. Canu, Philippe Garnier, William S. Kurth, Andrew J. Coates, Jan-Erik Wahlund, Centre d'étude spatiale des rayonnements (CESR), Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, Swedish Institute of Space Physics [Uppsala] (IRF), HELIOS - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Office for Space Research and Applications [Athens], Academy of Athens, Laboratoire de Physique des Plasmas (LPP), Université Paris-Sud - Paris 11 (UP11)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Sorbonne Université (SU)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Department of Physics and Astronomy [Iowa City], University of Iowa [Iowa City], Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), Mullard Space Science Laboratory (MSSL), University College of London [London] (UCL), Space and Atmospheric Physics Group [London], Blackett Laboratory, Imperial College London-Imperial College London, Space Science and Engineering Division [San Antonio], Southwest Research Institute [San Antonio] (SwRI), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
Subjects: Atmospheric Science, 010504 meteorology & atmospheric sciences, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Magnetosphere, 01 natural sciences, Astrobiology, symbols.namesake, Magnetosheath, Physics::Plasma Physics, 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), Langmuir probe, lcsh:Science, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Physics, [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], Waves in plasmas, lcsh:QC801-809, Geology, Astronomy and Astrophysics, lcsh:QC1-999, lcsh:Geophysics. Cosmic physics, Space and Planetary Science, Physics::Space Physics, symbols, Magnetopause, lcsh:Q, Astrophysics::Earth and Planetary Astrophysics, Ionosphere, Titan (rocket family), lcsh:Physics, Radio wave
Abstract: The Cassini mission has provided much information about the Titan environment, with numerous low altitude encounters with the moon being always inside the magnetosphere. The only encounter taking place outside the magnetopause, in the magnetosheath, occurred the 13 June 2007 (T32 flyby). This paper is dedicated to the analysis of the Radio and Plasma Wave investigation data during this specific encounter, in particular with the Langmuir probe, providing a detailed picture of the cold plasma environment and of Titan's ionosphere with these unique plasma conditions. The various pressure terms were also calculated during the flyby. The comparison with the T30 flyby, whose geometry was very similar to the T32 encounter but where Titan was immersed in the kronian magnetosphere, reveals that the evolution of the incident plasma has a significant influence on the structure of the ionosphere, with in particular a change of the exo-ionospheric shape. The electrical conductivities are given along the trajectory of the spacecraft and the discovery of a polar plasma cavity is reported.
Published: 2009
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7. Transport of Solar Wind H+ and He++ Ions across Earth's Bow Shock

Author: H. E. Kim, Henri Rème, George K. Parks, Yuqiang Ma, S. Y. Fu, P. Canu, M. L. Goldstein, Ying Liu, Zhongwei Yang, Ensang Lee, Iannis Dandouras, J. Hong, N. Lin, Laboratoire de Physique des Plasmas (LPP), Université Paris-Sud - Paris 11 (UP11)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Sorbonne Université (SU)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
Subjects: Physics, Shock wave, 010504 meteorology & atmospheric sciences, Astrophysics::High Energy Astrophysical Phenomena, Astronomy and Astrophysics, 01 natural sciences, Astrobiology, Ion, Solar wind, 13. Climate action, Space and Planetary Science, [PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], 0103 physical sciences, Physics::Space Physics, Bow shock (aerodynamics), [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, Earth (classical element), Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences
Abstract: International audience; We have investigated the dependence of mass, energy, and charge of solar wind (SW) transport across Earth?s bow shock. An examination of 111 crossings during quiet SW in both quasi-perpendicular and quasi-parallel shock regions shows that 64 crossings had various degrees of heating and thermalization of SW. We found 22 crossings where the SW speed was
Published: 2016
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8. On magnetospheric electron impact ionisation and dynamics in Titan's ram-side and polar ionosphere – a Cassini case study

Author: Ronan Modolo, Dirk Lummerzheim, J. H. Waite, Roger V. Yelle, Andrew J. Coates, Thomas E. Cravens, P. Canu, Ingo Müller-Wodarg, D. T. Young, Gethyn R. Lewis, Jan-Erik Wahlund, M. K. Dougherty, Marina Galand, K. Ågren, William S. Kurth, Cesar Bertucci, Swedish Institute of Space Physics [Uppsala] (IRF), Geophysical Institute [Fairbanks], University of Alaska [Fairbanks] (UAF), Space and Atmospheric Physics Group [London], Blackett Laboratory, Imperial College London-Imperial College London, Centre d'étude des environnements terrestre et planétaires (CETP), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Department of Physics and Astronomy [Iowa City], University of Iowa [Iowa City], Department of Physics and Astronomy [Lawrence Kansas], University of Kansas [Lawrence] (KU), Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, Department of Atmospheric, Oceanic, and Space Sciences [Ann Arbor] (AOSS), University of Michigan [Ann Arbor], University of Michigan System-University of Michigan System, Mullard Space Science Laboratory (MSSL), University College of London [London] (UCL), and Southwest Research Institute [San Antonio] (SwRI)
Subjects: Atmospheric Science, 010504 meteorology & atmospheric sciences, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Magnetosphere, Astrophysics, Electron, 01 natural sciences, 7. Clean energy, Astrobiology, Physics::Geophysics, symbols.namesake, Ionization, 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), lcsh:Science, 010303 astronomy & astrophysics, Electron ionization, 0105 earth and related environmental sciences, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Physics, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], lcsh:QC801-809, Geology, Astronomy and Astrophysics, lcsh:QC1-999, lcsh:Geophysics. Cosmic physics, 13. Climate action, Space and Planetary Science, Physics::Space Physics, symbols, Polar, lcsh:Q, Astrophysics::Earth and Planetary Astrophysics, Ionosphere, Titan (rocket family), lcsh:Physics, Exosphere
Abstract: We present data from the sixth Cassini flyby of Titan (T5), showing that the magnetosphere of Saturn strongly interacts with the moon's ionosphere and exo-ionosphere. A simple electron ionisation model provides a reasonable agreement with the altitude structure of the ionosphere. Furthermore, we suggest that the dense and cold exo-ionosphere (from the exobase at 1430 km and outward to several Titan radii from the surface) can be explained by magnetospheric forcing and other transport processes whereas exospheric ionisation by impacting low energy electrons seems to play a minor role.
Published: 2007
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9. Analysis of plasmaspheric plumes: CLUSTER and IMAGE observations

Author: Jean-Gabriel Trotignon, Iannis Dandouras, J. De Keyser, Fabien Darrouzet, M. W. Dunlop, Pierrette Décréau, Arnaud Masson, Dennis L. Gallagher, Mats André, Bill R. Sandel, Hiroshi Matsui, Viviane Pierrard, J. Cabrera, Joseph Lemaire, Jean-Louis Rauch, P. Canu, UCL - SST/IRMP - Institut de recherche en mathématique et physique, Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique (BIRA-IASB), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), NASA Marshall Space Flight Center (MSFC), Center for Space Radiations (CSR), Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, Centre d'étude spatiale des rayonnements (CESR), Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, Center for Space Radiations [Louvain-la-Neuve] (CSR), Université Catholique de Louvain = Catholic University of Louvain (UCL), Space Science and Technology Department [Didcot] (RAL Space), STFC Rutherford Appleton Laboratory (RAL), Science and Technology Facilities Council (STFC)-Science and Technology Facilities Council (STFC), Research and Scientific Support Department, ESTEC (RSSD), European Space Research and Technology Centre (ESTEC), European Space Agency (ESA)-European Space Agency (ESA), Centre d'étude des environnements terrestre et planétaires (CETP), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Swedish Institute of Space Physics [Uppsala] (IRF), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), and Agence Spatiale Européenne = European Space Agency (ESA)-Agence Spatiale Européenne = European Space Agency (ESA)
Subjects: Atmospheric Science, Electron density, Drift velocity, 010504 meteorology & atmospheric sciences, Plasmasphere, Plasma oscillation, 01 natural sciences, [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), lcsh:Science, 010303 astronomy & astrophysics, Image resolution, 0105 earth and related environmental sciences, Remote sensing, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Spacecraft, business.industry, Orientation (computer vision), lcsh:QC801-809, Geology, Astronomy and Astrophysics, Geodesy, lcsh:QC1-999, Plume, lcsh:Geophysics. Cosmic physics, Space and Planetary Science, Physics::Space Physics, lcsh:Q, business, lcsh:Physics
Abstract: Plasmaspheric plumes have been routinely observed by CLUSTER and IMAGE. The CLUSTER mission provides high time resolution four-point measurements of the plasmasphere near perigee. Total electron density profiles have been derived from the electron plasma frequency identified by the WHISPER sounder supplemented, in-between soundings, by relative variations of the spacecraft potential measured by the electric field instrument EFW; ion velocity is also measured onboard these satellites. The EUV imager onboard the IMAGE spacecraft provides global images of the plasmasphere with a spatial resolution of 0.1 RE every 10 min; such images acquired near apogee from high above the pole show the geometry of plasmaspheric plumes, their evolution and motion. We present coordinated observations of three plume events and compare CLUSTER in-situ data with global images of the plasmasphere obtained by IMAGE. In particular, we study the geometry and the orientation of plasmaspheric plumes by using four-point analysis methods. We compare several aspects of plume motion as determined by different methods: (i) inner and outer plume boundary velocity calculated from time delays of this boundary as observed by the wave experiment WHISPER on the four spacecraft, (ii) drift velocity measured by the electron drift instrument EDI onboard CLUSTER and (iii) global velocity determined from successive EUV images. These different techniques consistently indicate that plasmaspheric plumes rotate around the Earth, with their foot fully co-rotating, but with their tip rotating slower and moving farther out.
Published: 2006
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10. Density structures inside the plasmasphere: Cluster observations

Author: F. Darrouzet, P. M. E. Décréau, J. De Keyser, A. Masson, D. L. Gallagher, O. Santolik, B. R. Sandel, J. G. Trotignon, J. L. Rauch, E. Le Guirriec, P. Canu, F. Sedgemore, M. André, J. F. Lemaire, Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique (BIRA-IASB), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Research and Scientific Support Department, ESTEC (RSSD), European Space Research and Technology Centre (ESTEC), European Space Agency (ESA)-European Space Agency (ESA), NASA Marshall Space Flight Center (MSFC), Faculty of Mathematics and Physics [Praha/Prague], Charles University [Prague] (CU), Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, Centre d'étude des environnements terrestre et planétaires (CETP), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Danish Space Research Institute (DSRI), Swedish Institute of Space Physics [Uppsala] (IRF), Laboratoire de physique et chimie de l'environnement (LPCE), Université d'Orléans (UO)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), and Swedish Institute of Space Physics [Kiruna] (IRF)
Subjects: Atmospheric Science, Electron density, 010504 meteorology & atmospheric sciences, Density gradient, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Magnetosphere, Plasmasphere, 01 natural sciences, [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), lcsh:Science, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Remote sensing, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Physics, Spacecraft, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], business.industry, lcsh:QC801-809, Geology, Astronomy and Astrophysics, Space physics, lcsh:QC1-999, Computational physics, Plume, lcsh:Geophysics. Cosmic physics, Space and Planetary Science, Physics::Space Physics, Satellite, lcsh:Q, business, lcsh:Physics
Abstract: The electron density profiles derived from the EFW and WHISPER instruments on board the four Cluster spacecraft reveal density structures inside the plasmasphere and at its outer boundary, the plasmapause. We have conducted a statistical study to characterize these density structures. We focus on the plasmasphere crossing on 11 April 2002, during which Cluster observed several density irregularities inside the plasmasphere, as well as a plasmaspheric plume. We derive the density gradient vectors from simultaneous density measurements by the four spacecraft. We also determine the normal velocity of the boundaries of the plume and of the irregularities from the time delays between those boundaries in the four individual density profiles, assuming they are planar. These new observations yield novel insights about the occurrence of density irregularities, their geometry and their dynamics. These in-situ measurements are compared with global images of the plasmasphere from the EUV imager on board the IMAGE satellite.
Published: 2004
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11. In situ observations of high-Mach number collisionless shocks in space plasmas

Author: Nick Sergis, Lukasz Stawarz, Gethyn R. Lewis, Adam Masters, Steven J. Schwartz, Bertalan Zieger, M. K. Dougherty, Andrew J. Coates, Hiroshi Hasegawa, Alessandro Retinò, Masaki Fujimoto, P. Canu, Michelle F. Thomsen, Laboratoire de Physique des Plasmas (LPP), Université Paris-Sud - Paris 11 (UP11)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Sorbonne Université (SU)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
Subjects: Shock wave, Solar System, 010504 meteorology & atmospheric sciences, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics, 01 natural sciences, symbols.namesake, [PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], Saturn, 0103 physical sciences, Bow shock (aerodynamics), 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, Physics, Astronomy, Condensed Matter Physics, Shock waves in astrophysics, Solar wind, Nuclear Energy and Engineering, Mach number, Physics::Space Physics, symbols, Astrophysical plasma, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: International audience; Shock waves are widespread in collisionless space plasmas throughout the Universe. How particles are accelerated at these shocks has been the subject of much research attention. The dominant source of the high-energy particles that pervade our Galaxy (cosmic rays) is thought to be the high-Mach number collisionless shocks that form around young supernova remnants, but it is unclear how much the lower Mach number collisionless shock waves frequently encountered by spacecraft in Solar System space plasmas can tell us about particle acceleration in the higher Mach number regime. Here we review recent studies of the shock wave that stands in the solar wind in front of the planet Saturn (Saturn's bow shock), based on Cassini spacecraft observations. This review represents a new direction of shock physics research, with the potential to bridge the gap between Solar System and astrophysical shocks. These studies have confirmed that Saturn's bow shock is one of the strongest shocks in the Solar System, and a recent discovery indicates that electron acceleration at high-Mach numbers may occur irrespective of the upstream magnetic field geometry. This is important because astrophysical shocks can often only be studied remotely via emissions associated with accelerated electrons. We discuss possible future directions of this emerging sub-field of collisionless space plasma shock physics.
Published: 2013
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12. Reinterpretation of Slowdown of Solar Wind Mean Velocity in Nonlinear Structures Observed Upstream of Earth's Bow Shock

Author: J. B. Cao, P. Canu, George K. Parks, Iannis Dandouras, Matthew D. McCarthy, Henri Rème, J. Shi, N. Lin, Ensang Lee, J. Hong, Ying Liu, M. L. Goldstein, S. Y. Fu, Laboratoire de Physique des Plasmas (LPP), Université Paris-Sud - Paris 11 (UP11)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Sorbonne Université (SU)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
Subjects: Physics, Shock wave, education.field_of_study, 010504 meteorology & atmospheric sciences, Shock (fluid dynamics), Population, Astronomy and Astrophysics, Mechanics, Astrophysics, Bow shocks in astrophysics, 01 natural sciences, Solar wind, Space and Planetary Science, [PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], 0103 physical sciences, Electron temperature, Mean flow, education, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, Beam (structure), 0105 earth and related environmental sciences
Abstract: International audience; Two of the many features associated with nonlinear upstream structures are (1) the solar wind (SW) mean flow slows down and deviates substantially and (2) the temperature of the plasma increases in the structure. In this Letter, we show that the SW beam can be present throughout the entire upstream event maintaining a nearly constant beam velocity and temperature. The decrease of the velocity is due to the appearance of new particles moving in the opposite direction that act against the SW beam and reduce the mean velocity as computed via moments. The new population, which occupies a larger velocity space, also contributes to the second moment, increasing the temperature. The new particles include the reflected SW beam at the bow shock and another population of lower energies, accelerated nearby at the shock or at the boundary of the nonlinear structures.
Published: 2013
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13. Lessons learned from WHISPER relaxation sounder in ten years of CLUSTER mission

Author: G. Lointier, J. G. Trotignon, Jean-Louis Rauch, X. Vallieres, S. Kougblénou, P. Canu, Pierrette Décréau, Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Laboratoire de Physique des Plasmas (LPP), Université Paris-Saclay-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11)-École polytechnique (X)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)
Subjects: Physics, Frequency analysis, 010504 meteorology & atmospheric sciences, Magnetosphere, Plasmasphere, Plasma oscillation, Lower hybrid oscillation, 01 natural sciences, 7. Clean energy, law.invention, Magnetosheath, law, [PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], 0103 physical sciences, Satellite, Plasma diagnostics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Remote sensing
Abstract: International audience; The four WHISPER instruments, part of the Wave Experiment Consortium on board the multi satellite CLUSTER mission, include each a relaxation sounder aimed to measure with a good precision and reliability the frequency positions of F p , electron plasma frequency, and of F ce , electron gyro-frequency. Those quantities give access to electron density and intensity of magnetic field, key parameters defining local plasma regime. WHISPER sounder's design and realization, based on the expertise provided by successful missions operated in late seventies and eighties (GEOS, ISEE, Viking), is characterized by use of a processor devoted to on board frequency analysis via FFT. This choice makes those relaxation sounders unique of their kind, allowing in particular a complete plasma diagnostic to be made in only 1.5 s, almost one order of magnitude faster than in the past. The CLUSTER mission itself is unique, by its multi-point capability, and by its orbit, which along the mission allowed exploring a large variety of key regions of the magnetosphere. We present in this paper a few examples of WHISPER instrument behaviour and results, exploring in particular magnetosheath, polar cap, outer and inner plasmasphere. In the latter region, F p and F ce frequency values are far above the working frequency range of the instrument. This range, however, includes the lower hybrid frequency, F lh , which shows up as a clear resonance triggered by the sounder, and allows measurement of Ne whenever F p /F ce
Published: 2011
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14. Alfvén : Magnetosphere -Ionosphere Connection Explorers

Author: Dhiren Kataria, J. A. Davies, J. Manninen, Laurent Lamy, Betty Lanchester, Joachim Vogt, Yu. V. Khotyaintsev, Kirsti Kauristie, Mike Hapgood, Stephen E. Milan, E. Turunen, F. Mottez, T. Chust, Alain Roux, P. Louarn, Anastasios Anastasiadis, Masatoshi Yamauchi, Octav Marghitu, Milan Maksimovic, Anasuya Aruliah, Michel Parrot, R. Pottelette, Göran Marklund, E. A. Lucek, Vincent Génot, Maria Hamrin, Laurence Rezeau, Jean-Louis Pinçon, Christopher J. Owen, F. Pitout, Roberto Bruno, Gerhard Haerendel, P. Canu, Baptiste Cecconi, Ingrid Sandahl, I. Zouganelis, Philippe Zarka, Aurélie Marchaudon, Ioannis A. Daglis, Clare E. J. Watt, C. H. Perry, S. Kemble, C. Briand, Joran Moen, M. W. Dunlop, Rickard Lundin, Jim Wild, Olga Alexandrova, Sebastien Hess, Andrew Fazakerley, Tuija Pulkkinen, P.-L. Blelly, Nikolai Østgaard, Dominique Fontaine, Arne Pedersen, Holger Nilsson, I. J. Rae, Andrew Walsh, Hannu Koskinen, Colin Forsyth, Björn Gustavsson, Matthieu Berthomier, Ingmar Sandberg, Laboratoire de Physique des Plasmas (LPP), Université Paris-Sud - Paris 11 (UP11)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-École polytechnique (X)-Sorbonne Universités-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Mullard Space Science Laboratory (MSSL), University College of London [London] (UCL), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Atmospheric Physics Laboratory [UCL London], Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), ONERA, Finnish Meteorological Institute (FMI), Swedish Institute of Space Physics [Kiruna] (IRF), Max-Planck-Institut für Extraterrestrische Physik (MPE), Department of Physics and Astronomy [Leicester], University of Leicester, Laboratoire Univers et Théories (LUTH (UMR_8102)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de physique et chimie de l'environnement (LPCE), Université d'Orléans (UO)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), STFC Rutherford Appleton Laboratory (RAL), Science and Technology Facilities Council (STFC), Université Paris-Sud - Paris 11 (UP11)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-École polytechnique (X)-Sorbonne Universités-Sorbonne Université (SU)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Sorbonne Université (SU)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7), Université Paris-Saclay-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11)-École polytechnique (X)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)
Subjects: Cosmic Vision, 010504 meteorology & atmospheric sciences, Magnetosphere, 01 natural sciences, 7. Clean energy, Physics::Geophysics, [PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], High latitude, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, Physics, [PHYS]Physics [physics], Astronomy, Astronomy and Astrophysics, Plasma, Connection (mathematics), Solar wind, Space and Planetary Science, Physics::Space Physics, Astrophysics::Earth and Planetary Astrophysics, Ionosphere, Energy source, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: The aurorae are dynamic, luminous displays that grace the night skies of Earth’s high latitude regions. The solar wind emanating from the Sun is their ultimate energy source, but the chain of plasma physical processes leading to auroral displays is complex. The special conditions at the interface between the solar wind-driven magnetosphere and the ionospheric environment at the top of Earth’s atmosphere play a central role. In this Auroral Acceleration Region (AAR) persistent electric fields directed along the magnetic field accelerate magnetospheric electrons to the high energies needed to excite luminosity when they hit the atmosphere. The “ideal magnetohydrodynamics” description of space plasmas which is useful in much of the magnetosphere cannot be used to understand the AAR. The AAR has been studied by a small number of single spacecraft missions which revealed an environment rich in wave-particle interactions, plasma turbulence, and nonlinear acceleration processes, acting on a variety of spatio-temporal scales. The pioneering 4-spacecraft Cluster magnetospheric research mission is now fortuitously visiting the AAR, but its particle instruments are too slow to allow resolve many of the key plasma physics phenomena. The Alfvén concept is designed specifically to take the next step in studying the aurora, by making the crucial high-time resolution, multi-scale measurements in the AAR, needed to address the key science questions of auroral plasma physics. The new knowledge that the mission will produce will find application in studies of the Sun, the processes that accelerate the solar wind and that produce aurora on other planets.
Published: 2011
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15. Multi-spacecraft investigation of space turbulence: lessons from Cluster and input to the Cross- Scale mission

Author: Olivier Le Contel, N. Cornilleau-Wehrlin, J. L. Pinçon, P. Canu, Khurom Kiyani, Melvyn L. Goldstein, Fouad Sahraoui, Alain Roux, Thierry Dudok de Wit, Gérard Belmont, Laurence Rezeau, Patrick Robert, Laboratoire de Physique des Plasmas (LPP), Université Paris-Sud - Paris 11 (UP11)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Sorbonne Université (SU)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), NASA Goddard Space Flight Center (GSFC), Laboratoire de physique et chimie de l'environnement (LPCE), Université d'Orléans (UO)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre for Fusion Space and Astrophysics [Coventry] (CFSA), University of Warwick [Coventry], Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Physics, 010504 meteorology & atmospheric sciences, Spacecraft, Scale (ratio), business.industry, Astronomy and Astrophysics, Space (mathematics), 01 natural sciences, Space and Planetary Science, Aliasing, [PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], 0103 physical sciences, Physics::Space Physics, Cluster (physics), Tetrahedron, Wavenumber, Sensitivity (control systems), Aerospace engineering, business, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Remote sensing
Abstract: International audience; Investigating space plasma turbulence from single-point measurements is known to be characterized by unavoidable ambiguities in disentangling temporal and spatial variations. Solving this problem has been one of the major goals of the Cluster mission. For that purpose multipoint measurements techniques, such as the $k$-filtering, have been developed. Such techniques combine several time series recorded simultaneously at different points in space to estimate the corresponding energy density in the wavenumber space. Here we apply the technique to both simulated and Cluster magnetometer data in the solar wind (SW) and investigate the errors and limitations that arise due to the separation of the spacecraft and the quality of the tetrahedral configuration. Specifically, we provide an estimation of the minimum and maximum scales that can be accurately measured given a specific distance between the satellites and show the importance of the geometry of the tetrahedron and the relationship of that geometry to spatial aliasing. We also present recent results on characterizing small scale SW turbulence and provide scientific arguments supporting the need of new magnetometers having better sensitivity than the existing ones. Throughout the paper we emphasize technical challenges and their solutions that can be considered for a better preparation of the Cross- Scale mission.
Published: 2011
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16. Observation and theoretical modeling of electron scale solar wind turbulence

Author: P. Canu, Fouad Sahraoui, Melvyn L. Goldstein, K. Abdul-Kader, Patrick Robert, Gérard Belmont, Laurence Rezeau, Laboratoire de Physique des Plasmas (LPP), Université Paris-Sud - Paris 11 (UP11)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Sorbonne Université (SU)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
Subjects: Physics, 010504 meteorology & atmospheric sciences, Turbulence, General Engineering, Energy Engineering and Power Technology, K-omega turbulence model, Astrophysics, Dissipation, Kinetic energy, 7. Clean energy, 01 natural sciences, Power law, Computational physics, Solar wind, Cascade, [PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], 0103 physical sciences, Physics::Space Physics, Magnetohydrodynamics, 010306 general physics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 0105 earth and related environmental sciences
Abstract: Turbulence at MagnetoHydroDynamics (MHD) scales in the solar wind has been studied for more than three decades, using data analysis, theoretical and numerical modeling. However, smaller scales have not been explored until very recently. Here, we review recent results on the first observation of cascade and dissipation of the solar wind turbulence at the electron scales. Thanks to the high resolution magnetic and electric field data of the Cluster spacecraft, we computed the spectra of turbulence up to ∼ 100 Hz (in the spacecraft reference frame) and found evidence of energy dissipation around the Doppler-shifted electron gyroscale f ρ e . Before its dissipation, the energy is shown to undergo two cascades: a Kolmogorov-like cascade with a scaling f − 1.6 above the proton gyroscale, and a new f − 2.3 cascade at the sub-proton and electron gyroscales. Above f ρ e the spectrum has a steeper power law ∼ f − 4.1 down to the noise level of the instrument. Solving numerically the linear Maxwell–Vlasov equations combined with recent theoretical predictions of the Gyro-Kinetic theory, we show that the present results are consistent with a scenario of a quasi-two-dimensional cascade into Kinetic Alfven modes (KAW). New analyses of other data sets, where the Cluster separation (of about ∼ 200 km ) allowed us to explore the sub-proton scales using the k-filtering technique, and to confirm the 2D nature of the turbulence at those scales.
Published: 2011
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17. Cluster observations of outflowing electron distributions and broadband electrostatic emissions above the polar cap

Author: Dominique Fontaine, Gérard Belmont, P. Canu, and A. Teste
Subjects: Physics, Range (particle radiation), 010504 meteorology & atmospheric sciences, business.industry, Electron, Plasma oscillation, 01 natural sciences, Instability, Computational physics, Geophysics, Optics, 0103 physical sciences, Cluster (physics), Cathode ray, General Earth and Planetary Sciences, Ionosphere, business, 010303 astronomy & astrophysics, Beam (structure), 0105 earth and related environmental sciences
Abstract: [1] We investigate the excellent correlation between ionospheric upgoing electron beams and broadband electrostatic emissions (0-6 kHz) observed by Cluster, at ~5 to 9 Earth's radii above the polar cap. In the absence of detailed, high time resolution waveform data in that region, we precisely analyzed several electron beams to obtain information concerning wave-particle interactions. Our results indicate that these beams are extremely variable and occasionally show multiple components. The processes involved might then occur on very short time scales, of the order of or shorter than sampling rates, typically 100 ms. We suggest that non linearities are at the origin of the spread of the frequency range of the waves simultaneously observed, as well as of the beam variability. We conclude that these electron beams are likely to destabilize Langmuir waves and, by the non-linear evolution of the electron bump-on-tail instability, could be responsible for the appearance of electrostatic solitary waves above the polar cap.
Published: 2010
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18. Wave emissions at half electron gyroharmonics in the equatorial plasmasphere region: CLUSTER observations and statistics

Author: F. El-Lemdani Mazouz, Pierrette Décréau, P. Canu, Xavier Vallières, Jean-Louis Rauch, Jean-Gabriel Trotignon, X. Suraud, Fabien Darrouzet, Laboratoire de physique et chimie de l'environnement (LPCE), Université d'Orléans (UO)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique des Plasmas (LPP), Université Paris-Sud - Paris 11 (UP11)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Sorbonne Université (SU)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
Subjects: Atmospheric Science, 010504 meteorology & atmospheric sciences, Meteorology, Aerospace Engineering, Magnetosphere, Plasmasphere, Astrophysics, 01 natural sciences, [PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], 0103 physical sciences, Pitch angle, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Physics, Spectral signature, Scattering, Astronomy and Astrophysics, Geophysics, Amplitude, Earth's magnetic field, 13. Climate action, Space and Planetary Science, Physics::Space Physics, Harmonic, General Earth and Planetary Sciences, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: International audience; Intense (n 1/2) fce emissions are a common phenomenon observed in the terrestrial inner magnetosphere. One of their interests is their possible effect in the pitch angle scattering of plasmasheet keV-electron, leading to diffuse auroras. In this paper, we present CLUSTERs point of view about this topic, in the equatorial region of the plasmasphere, via a statistical study using 3 years of data. Spectral characteristics of these waves, which represent an important clue concerning their generation mechanism, are obtained using WHISPER data near perigee. Details on the wave spectral signature are shown in an event study, in particular their splitting in fine frequency bands. The orbit configuration of the four spacecraft offers a complete sampling on all MLT sectors. A higher occurrence rate of the emissions in the dawn sector and their confinement to the geomagnetic equator, pointed out in previous studies, are confirmed and described with additional details. The proximity of emission sites, both to the plasmapause layer and to the geomagnetic equator surface, seems to be of great importance in the behaviour of the (n 1/2) fce wave characteristics. Our study indicates for the first time, that both the intensity of (n 1/2) fce emissions, and the number of harmonic bands they cover, are increasing as the observation point is located further away outside from the plasmapause layer. Moreover, a study of the wave intensity in the first harmonic band (near 3/2 fce) shows higher amplitude for these emissions than previous published values, these emissions can play a role in the scattering of hot electrons. Finally, geomagnetic activity influence, studied via time series of the Dst index preceding observations, indicates that (n 1/2) fce emission events are observed at CLUSTER position under moderate geomagnetic activity conditions, no specific Dst time variation being required.
Published: 2009
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19. Medium-latitude sources of plasmaspheric nonthermal continuum radiations observed close to harmonics of the electron gyrofrequency

Author: P. Canu, X. Vallières, P. Décréau, A. Rochel, and S. Grimald
Subjects: Atmospheric Science, 010504 meteorology & atmospheric sciences, Soil Science, Magnetic dip, Magnetosphere, Auroral kilometric radiation, Plasmasphere, Electron, Aquatic Science, Radiation, Oceanography, 01 natural sciences, Electromagnetic radiation, 010305 fluids & plasmas, Latitude, Geochemistry and Petrology, 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, Physics, Ecology, Paleontology, Forestry, Computational physics, Geophysics, 13. Climate action, Space and Planetary Science, Physics::Space Physics, Atomic physics
Abstract: [1] Nonthermal continuum (NTC) radiation is, with auroral kilometric radiation (AKR), one of the two electromagnetic emissions generated within the Earth’s magnetosphere and radiated into space. It is generally believed that NTC is emitted in the plasmapause density gradient after conversion of intense electrostatic waves, present near the magnetic equator, into electromagnetic waves. In this paper, we present a specific type of NTC event, of infrequent occurrence, displaying a finger-like pattern not yet reported: banded emissions peaking at exact multiples of a common frequency, df, which decrease inbound toward the plasmapause boundary layer (PPBL). Analysis is presented that indicates that the corresponding sources are nearby sites of the PPBL where the local electron gyrofrequency fce equals df. The sources are radiating beams of limited cone angle size. The NTC sources for this event are shown to be located at about 20 magnetic latitude. This illustrates that the PPBL is active in radiating NTC waves not only near the magnetic equator but also up to the medium-latitude range.
Published: 2008
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20. Plasma environment in the wake of Titan from hybrid simulation: A case study

Author: A. P. Matthews, Jan-Erik Wahlund, Cesar Bertucci, D. A. Gurnett, Ronan Modolo, William S. Kurth, Gérard Chanteur, P. Canu, Swedish Institute of Space Physics [Uppsala] (IRF), Centre d'étude des environnements terrestre et planétaires (CETP), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Department of Physics and Astronomy, University of Iowa, University of Iowa [Iowa City], School of Physics, University of KwaZulu-Natal, University of KwaZulu-Natal (UKZN), Space and Atmospheric Physics Group [London], Blackett Laboratory, and Imperial College London-Imperial College London
Subjects: 010504 meteorology & atmospheric sciences, Meteorology, media_common.quotation_subject, Electron, Wake, 01 natural sciences, Asymmetry, Ion, [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], symbols.namesake, Physics::Plasma Physics, 0103 physical sciences, hybrid simulation, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, media_common, Physics, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Plasma, Computational physics, Magnetic field, Geophysics, 13. Climate action, Physics::Space Physics, symbols, General Earth and Planetary Sciences, Astrophysics::Earth and Planetary Astrophysics, Ionosphere, Titan, Titan (rocket family), atmospheric interaction
Abstract: On 26 December 2005, the Cassini spacecraft flew through Titan's plasma wake and revealed a complex and dynamic region. Observations suggest a strong asymmetry which seems to be displaced from the ideal position of the wake. Two distinct plasma regions are identified with a significant difference on the electron number density and on the plasma composition. Simulation results using a three-dimensional and multi-species hybrid model, performed in conditions similar to those encountered during the flyby, are presented and compared to the observations. An acceptable agreement is shown between the model predictions and the observations. We suggest that the observed asymmetries, in terms of density and plasma composition, are mainly caused by the a combination of the asymmetry in the ion/electron production rate and the magnetic field morphology, where the first plasma region is connected to the dayside hemisphere of Titan's ionosphere while the other is connected to the nightside hemisphere.
Published: 2007
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21. Source of whistler emissions at the dayside magnetopause

Author: P. Canu, Mats André, Andris Vaivads, Christopher J. Owen, Ondrej Santolik, Gabriella Stenberg, and M. W. Dunlop
Subjects: Physics, 010504 meteorology & atmospheric sciences, Flux tube, Whistler, Field line, Astrophysics::High Energy Astrophysical Phenomena, Magnetosphere, Magnetic reconnection, Geophysics, 01 natural sciences, 7. Clean energy, Magnetic flux, Computational physics, Magnetosheath, Physics::Plasma Physics, 13. Climate action, Physics::Space Physics, 0103 physical sciences, General Earth and Planetary Sciences, Magnetopause, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences
Abstract: Observations of whistler emissions are common in the magnetosphere near the dayside magnetopause. We show that one of the major source regions for these emissions is magnetic field minima that form along magnetic flux tubes at high latitudes. Using multispacecraft Cluster observations we experimentally confirm for the first time the existence of the magnetic field minima at high latitudes and we show that whistler emissions propagate away from the magnetic field minima. The strongest whistler emissions are observed on the magnetospheric flux tubes that are newly opened due to the magnetic reconnection. These flux tubes still have a density of magnetospheric plasma, but part of the high energy magnetospheric electrons have already been lost from the flux tubes. The partial loss of high energy electrons most probably causes anisotropy in electron distributions at high energies which should be the source of whistler emissions. Whistler emissions on opened flux tubes disappear as soon as the plasma density of flux tubes increases due to the entering of magnetosheath ions. We speculate that whistler emissions can most probably be used to trace the dynamics of the first opened field lines and thus the dynamics of magnetic reconnection sites.
Published: 2007
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22. CLUSTER observations of electron outflowing beams carrying downward currents above the polar cap by northward IMF

Author: Andrew Fazakerley, Romain Maggiolo, Jean-André Sauvaud, Dominique Fontaine, A. Teste, P. Canu, Centre d'étude des environnements terrestre et planétaires (CETP), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre d'étude spatiale des rayonnements (CESR), Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, Mullard Space Science Laboratory (MSSL), University College of London [London] (UCL), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)
Subjects: Atmospheric Science, 010504 meteorology & atmospheric sciences, Field line, Astrophysics::High Energy Astrophysical Phenomena, Magnetosphere, Astrophysics, Electron, 01 natural sciences, Earth radius, 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), Interplanetary magnetic field, lcsh:Science, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Physics, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, lcsh:QC801-809, Geology, Astronomy and Astrophysics, Geophysics, Plasma, lcsh:QC1-999, lcsh:Geophysics. Cosmic physics, 13. Climate action, Space and Planetary Science, Physics::Space Physics, Polar, lcsh:Q, Ionosphere, lcsh:Physics
Abstract: Above the polar cap, at about 5–9 Earth radii (RE) altitude, the PEACE experiment onboard CLUSTER detected, for the first time, electron beams outflowing from the ionosphere with large and variable energy fluxes, well collimated along the magnetic field lines. All these events occurred during periods of northward or weak interplanetary magnetic field (IMF). These outflowing beams were generally detected below 100 eV and typically between 40 and 70 eV, just above the photoelectron level. Their energy gain can be explained by the presence of a field-aligned potential drop below the spacecraft, as in the auroral zone. The careful analysis of the beams distribution function indicates that they were not only accelerated but also heated. The parallel heating is estimated to about 2 to 20 eV and it globally tends to increase with the acceleration energy. Moreover, WHISPER observed broadband electrostatic emissions around a few kHz correlated with the outflowing electron beams, which suggests beam-plasma interactions capable of triggering plasma instabilities. In presence of simultaneous very weak ion fluxes, the outflowing electron beams are the main carriers of downward field-aligned currents estimated to about 10 nA/m2. These electron beams are actually not isolated but surrounded by wider structures of ion outflows. All along its polar cap crossings, Cluster observed successive electron and ion outflows. This implies that the polar ionosphere represents a significant source of cold plasma for the magnetosphere during northward or weak IMF conditions. The successive ion and electron outflows finally result in a filamented current system of opposite polarities which connects the polar ionosphere to distant regions of the magnetosphere.
Published: 2007
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23. Solitary electromagnetic pulses detected with super-Alfvénic flows in Earth's geomagnetic tail

Author: C. Gurgiolo, M. L. Goldstein, P. Canu, E. A. Lucek, M. Wilber, Andrew Fazakerley, H. Rème, George K. Parks, Pierrette Décréau, Nicole Cornilleau-Wehrlin, I. Dandouras, N. Lin, Ensang Lee, F. S. Mozer, Centre d'étude spatiale des rayonnements (CESR), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Centre d'étude des environnements terrestre et planétaires (CETP), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de physique et chimie de l'environnement (LPCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, and Université d'Orléans (UO)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Physics, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], 010504 meteorology & atmospheric sciences, Plasma sheet, General Physics and Astronomy, Bow shocks in astrophysics, 01 natural sciences, Electromagnetic radiation, [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Solar wind, Current sheet, Earth's magnetic field, Physics::Plasma Physics, Physics::Space Physics, 0103 physical sciences, Magnetopause, Atomic physics, Ionosphere, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences
Abstract: International audience; Solitary nonlinear (B=B 1) electromagnetic pulses have been detected in Earth's geomagnetic tail accompanying plasmas flowing at super-Alfvénic speeds. The pulses in the current sheet had durations of 5 s, were left-hand circularly polarized, and had phase speeds of approximately the Alfvén speed in the plasma frame. These pulses were associated with a field-aligned current J k and observed in low density (0:3 cm ÿ3), high temperature (T e T i 3 10 7 K), and 10 plasma that included electron and ion beams streaming along B. The wave activity was enhanced from below the ion cyclotron frequency to electron cyclotron and upper hybrid frequencies. The detailed properties suggest the pulses are non-linearly steepened ion cyclotron or Alfvén waves. We present first observations of solitary electromagnetic (EM) pulses detected in the Earth's geomagnetic tail during intervals of super-Alfvénic flows, where the perpendicular flow V ? exceeds the Alfvén speed V A. Most flow speeds are sub-Alfvénic and can be explained by recon-nection theories and models [1]. However, plasmas occasionally flow faster than V A [2]. The significance of V ? > V A flows and the possible nonlinear effects that might accompany them have not been discussed. Solitary waves are signatures of nonlinear interactions, and they can shed light on the elusive current sheet dynamics that drive the global aurora when Earth becomes an intense radio emitter and electrons are accelerated to hundreds of keV and ions to several MeV [3,4]. Solitary EM waves have been observed in comets and also in Earth's ionosphere [5,6], and Debye scale electro-static solitary waves are ubiquitous in the solar wind, bow shock, plasma sheet boundary layer (PSBL), and the auro-ral ionosphere [7-9]. Unipolar and bipolar wave packets have been detected in the PSBL, and magnetosonic soli-tons at the magnetopause [10,11]. However, there have been no reports of solitary pulses accompanying flows in which V ? > V A in the Earth's geomagnetic tail. A random sampling of cluster data of fast flowing plasmas indicates that V ? > V A flows occur when the geomag-netic tail is undergoing large fluctuations (but V ? > V A speeds are not always observed when and where large fluctuations occur). High-time resolution E and B fields during a number of events indicate that the EM pulses occur concurrently with V ? > V A flows in the current sheet (CS) while electrons and ions are streaming along B and wave activity is enhanced. The data in Fig. 1 are spin-averaged (4 s) from Cluster 1 (SC1) located at a tail distance of 19R E (R E Earth's radius). The ion bulk parameters are obtained by integrating the 3D distributions over the velocity space [12]. Measurements here were made in a thin CS (400 km) during an aurora [13]. SC1, initially in the plasma sheet PRL 98, 265001 (2007)
Published: 2007
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24. A quantitative test of Jones NTC beaming theory using CLUSTER constellation

Author: Fabien Darrouzet, S. Grimald, C. C. Harvey, P. Canu, X. Suraud, Xavier Vallières, Pierrette Décréau, Laboratoire de physique et chimie de l'environnement (LPCE), Université d'Orléans (UO)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre d'étude des environnements terrestre et planétaires (CETP), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique (BIRA-IASB), Centre d'étude spatiale des rayonnements (CESR), Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)
Subjects: Atmospheric Science, 010504 meteorology & atmospheric sciences, Magnetosphere, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Auroral kilometric radiation, Astrophysics, 01 natural sciences, 03 medical and health sciences, Position (vector), Earth and Planetary Sciences (miscellaneous), Ligand cone angle, lcsh:Science, 030304 developmental biology, 0105 earth and related environmental sciences, Physics, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, 0303 health sciences, Radio window, lcsh:QC801-809, Ecliptic, Triangulation (social science), Geology, Astronomy and Astrophysics, lcsh:QC1-999, lcsh:Geophysics. Cosmic physics, Space and Planetary Science, lcsh:Q, lcsh:Physics, Radio wave
Abstract: Non-thermal continuum (NTC) radiation is, with auroral kilometric radiation (AKR), one of the two electromagnetic emissions generated within the Earth's magnetosphere and radiated into space. The location of the source of NTC has been sought for several decades, with only limited success. The constellation formed by the four CLUSTER spacecraft provides the possibility of triangulation in the vicinity of the source, thus allowing progress in source localisation, while simultaneously revealing the beaming properties of NTC radio sources. We present a case event showing two beams localised on opposite sides of the magnetic equator. At any selected frequency, triangulation points to a single region source of small size. Its position is compatible with the range of possible loci of sources predicted by the radio window theory of Jones (1982) in a frame of constraints relaxed from the simple sketch proposed in early works. The analysis of similar observations from the Dynamics Explorer 1 by Jones et al. (1987) enabled the authors to claim validation of the radio window theory. CLUSTER observations, however, reveal a large beaming cone angle projected onto the ecliptic plane, a feature unobservable by Dynamics Explorer which had a different spin axis orientation. According to the radio window theory, such a large observed cone angle can only be formed by a series of point sources, each beaming in a narrow cone angle. This study demonstrates the difficulty of validating NTC linear generation mechanisms using global beaming properties alone.
Published: 2007
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25. Far plasma wake of Titan from the RPWS observations: A case study

Author: Rolf Boström, Gethyn R. Lewis, D. A. Gurnett, William S. Kurth, Ronan Modolo, P. Canu, Jan-Erik Wahlund, Andrew J. Coates, Swedish Institute of Space Physics [Uppsala] (IRF), Centre d'étude des environnements terrestre et planétaires (CETP), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Department of Physics and Astronomy, University of Iowa, University of Iowa [Iowa City], Mullard Space Science Laboratory (MSSL), and University College of London [London] (UCL)
Subjects: 010504 meteorology & atmospheric sciences, magnetosphere/ionosphere interaction, Magnetosphere, Electron, Astrophysics, Wake, 01 natural sciences, 7. Clean energy, [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], symbols.namesake, 0103 physical sciences, Langmuir probe, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Physics, magnetosphere interaction with satellites and rings, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Waves in plasmas, instruments and techniques, Geophysics, Plasma, 13. Climate action, symbols, General Earth and Planetary Sciences, Ionosphere, Titan (rocket family), Titan
Abstract: The Titan's plasma wake has been investigated using observations from the Radio and Plasma Wave Science (RPWS) instrument onboard the Cassini spacecraft during one Titan flyby on December 26, 2005. The Langmuir Probe and the wideband receiver suggest a strong asymmetry of the plasma wake, which is displaced from the ideal wake. Two distinct structures are identified inbound and outbound of the flyby with significantly different electron number densities (ne). The maximum electron number density reached 14 cm−3 on the Saturn side, connected to the sunlit ionosphere, while on the opposite side of Saturn observations indicate a density smaller than 2 cm−3. Other derived parameters of the Langmuir probe analysis suggest also a difference in plasma composition between the two structures, where heavy and light ions dominate the Saturn and anti-Saturn side respectively. The total ion outflow is estimated at 2–7 × 1025 ions/s assuming a cylindrical geometry for the plasma wake.
Published: 2007
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26. Density holes in the upstream solar wind

Author: Ensang Lee, George K. Parks, Nicole Cornilleau-Wehrlin, J. Cao, P. Décréau, F. S. Mozer, Philippe Escoubet, H. Rème, Iannis Dandouras, M. L. Goldstein, N. Lin, M. Wilber, P. Canu, E. A. Lucek, Space Sciences Laboratory [Berkeley] (SSL), University of California [Berkeley], University of California-University of California, Blackett Laboratory, Imperial College London, Centre d'étude spatiale des rayonnements (CESR), Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, State Key Laboratory for Space Weather [Beijing] (SKSW), National Space Science Center [Beijing] (NSSC), Chinese Academy of Sciences [Beijing] (CAS)-Chinese Academy of Sciences [Beijing] (CAS), Centre d'étude des environnements terrestre et planétaires (CETP), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de physique et chimie de l'environnement (LPCE), Université d'Orléans (UO)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), NASA Goddard Space Flight Center (GSFC), European Space Agency (ESA), University of California [Berkeley] (UC Berkeley), University of California (UC)-University of California (UC), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), State Key Laboratory of Space Weather [Beijing] (SKSW), Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), and Agence Spatiale Européenne = European Space Agency (ESA)
Subjects: Physics, 010504 meteorology & atmospheric sciences, Shock (fluid dynamics), Astrophysics::High Energy Astrophysical Phenomena, Astronomy, Coronal hole, Bow shocks in astrophysics, 01 natural sciences, Molecular physics, symbols.namesake, Solar wind, Mach number, [SDU]Sciences of the Universe [physics], 0103 physical sciences, Physics::Space Physics, symbols, Magnetopause, Particle, Astrophysical plasma, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences
Abstract: International audience; Larmor size transient structures with depletions as large as 99% of ambient solar wind density levels occur commonly upstream of Earth’s collisionless bow shock. These “density holes” have a mean duration of ∼17.9 ± 10.4s but holes as short as 4s have been observed. The average fractional density depletion (δn/n) inside the holes is ∼0.68 ± 0.14. The density of the upstream edge moving in the sunward direction can be enhanced by five or more times the solar wind density. Particle distributions show the steepened edge can behave like a shock, and measured local field geometries and Mach number support this view. Similarly shaped magnetic holes accompany the density holes indicating strong coupling between fields and particles. The density holes are only observed with upstream particles, suggesting that back‐streaming particles interacting with the solar wind are important.
Published: 2007
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27. Rapidly moving sources of upper band ELF/VLF chorus near the magnetic equator

Author: P. Canu, Umran S. Inan, M. Platino, Jolene S. Pickett, T. F. Bell, Space, Telecommunications, and Radioscience Laboratory (STAR Lab), Stanford University, Department of Physics and Astronomy, University of Iowa, University of Iowa [Iowa City], Centre d'étude des environnements terrestre et planétaires (CETP), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), and National Aeronautics and Space Administration (parent grant NAG5-9974 atthe University of Iowa and subcontract 4000061641 to StanfordUniversity)
Subjects: Atmospheric Science, chorus waves, sources of chorus, 010504 meteorology & atmospheric sciences, Field line, Soil Science, Magnetic dip, Aquatic Science, Oceanography, 01 natural sciences, L-shell, [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], symbols.namesake, Geochemistry and Petrology, 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, Physics, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Ecology, Spacecraft, biology, business.industry, Chorus, Paleontology, Forestry, whistler mode propagation, Geodesy, biology.organism_classification, Computational physics, Geophysics, Space and Planetary Science, Auroral chorus, Physics::Space Physics, Dawn chorus, symbols, business, Doppler effect
Abstract: [1] Multiple simultaneous wideband (Gurnett et al., 2001) measurements on the Cluster spacecraft of upper band chorus emissions near the magnetic equator (at magnetic latitudes between −20° and 10° and L shells ranging between L = 4 and L = 5) are used to deduce the properties of the compact source regions of ELF/VLF chorus emissions. The frequency differences exhibited by the same chorus emissions observed on different spacecraft are interpreted (Inan et al., 2004) in terms of a differential Doppler shift, using a simple model involving rapidly moving sources traveling at speeds comparable to the parallel resonant velocity of counter-streaming gyroresonant electrons. Cluster observations are used to determine the location and extent along the Earth's magnetic field lines of the source of chorus. Frequency and time differences between spacecraft are interpreted as a direct consequence of the rapid motion of highly localized source regions of chorus. In this paper, we examine the previously presented model of rapid motion of sources of chorus, extending the calculations to a three-dimensional space, using measurements of the four Cluster spacecraft. These calculations of source location and velocity as a function of frequency indicate that chorus sources move a distance of ∼6000 km along the field lines. The emitted chorus waves at the source are assumed to have a wide range of wave normal angles, but the rays reaching the spacecraft seem to be the ones with lower angles (with some exceptions). The ranges of velocity obtained vary with frequency around values ranging from ∼0.01c to ∼0.04c.
Published: 2006
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28. Narrowband Z-mode emissions interior to Saturn's plasma torus

Author: P. Canu, Michael D. Desch, William M. Farrell, M. L. Kaiser, D. A. Gurnett, William S. Kurth, NASA Goddard Space Flight Center (GSFC), Department of Physics and Astronomy [Iowa City], University of Iowa [Iowa City], Centre d'étude des environnements terrestre et planétaires (CETP), and Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Atmospheric Science, 010504 meteorology & atmospheric sciences, Meteorology, Soil Science, Magnetosphere, Astrophysics, Aquatic Science, Oceanography, Plasma oscillation, 01 natural sciences, Electromagnetic radiation, plasma waves, [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], 03 medical and health sciences, Narrowband, Geochemistry and Petrology, Saturn, Earth and Planetary Sciences (miscellaneous), 030304 developmental biology, 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, Physics, 0303 health sciences, Ecology, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Waves in plasmas, Paleontology, Forestry, Torus, Plasma, Geophysics, 13. Climate action, Space and Planetary Science, Physics::Space Physics, Cassini
Abstract: [1] During Cassini's close approach to Saturn, on 1 July 2004, a set of narrow bandwidth plasma emissions were detected by the Radio and Plasma Wave Science (RPWS) instrument in the inner magnetosphere. These discrete tones were detected between 3 and 70 kHz, with individual tone bandwidths as low as a few hundred Hertz. The tones persisted for long times (∼1 hour) as Cassini flew in planetocentric radial distances of less than 2.5 Rs. During this time at lower radial distances, the spacecraft passed inside the inner edge of a clear and distinct plasma torus; this torus is located between 2.2 and ∼10 Rs. We describe the emissions, and demonstrate that the mode of propagation is the Z-mode. The emissions are found to originate at locations where electron plasma oscillations along the plasma torus edge are relatively intense. We describe a mechanism for fp electrostatic-to-electromagnetic wave conversion to explain the origin of the narrowband Z-mode tones. The tones allow remote-sensing of the plasma torus and indicate that the torus is dynamic, with changes in density in the tens of percent over the course of an hour.
Published: 2005
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29. Whistlers observed by the Cluster spacecraft outside the plasmasphere

Author: P. Canu, M. Platino, Umran S. Inan, T. F. Bell, Pierrette Décréau, D. A. Gurnett, Jolene S. Pickett, Space, Telecommunications, and Radioscience Laboratory (STAR Lab), Stanford University, Department of Physics and Astronomy [Iowa City], University of Iowa [Iowa City], Centre d'étude des environnements terrestre et planétaires (CETP), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), and National Aeronautics and Space Administration ( grant NAG5-9974) atthe University of Iowa, and with subcontract 4000061641 to StanfordUniversity.
Subjects: Atmospheric Science, 010504 meteorology & atmospheric sciences, Whistler, Soil Science, Plasmasphere, Aquatic Science, Oceanography, 01 natural sciences, Latitude, [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Geochemistry and Petrology, 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), 010306 general physics, Dispersion (water waves), 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, Physics, Ecology, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Relaxation (NMR), Paleontology, Forestry, Plasma, Geophysics, Lightning, Computational physics, Space and Planetary Science, Ionosphere
Abstract: International audience; Lightning generated whistlers are ubiquitous within the plasmasphere at both highand low altitudes, and these waves propagate efficiently in both ducted and nonductedmodes. On the other hand, in the magnetospheric region outside the plasmasphere,lightning-generated whistlers are commonly observed at low altitudes (up to 6000 km)but only rarely at higher altitudes near the magnetic equatorial plane. The reasons forthe lack of these waves at higher altitudes are not well understood. In the presentpaper we use data from the Wide Band Plasma (WBD) instruments on the four Clusterspacecraft to study the characteristics of lightning-generated whistlers observed on 4 separatedays in 2001 at L shells ranging from L =4toL = 5, magnetic latitudes ranging from20 to 10, and Kp indices ranging from 3 to 6. The propagation paths of thelightning-generated whistlers are determined using a two-dimensional ray-tracing modelto calculate the ray paths and group delays from the lower ionosphere to each of thefour Cluster spacecraft over a range of frequencies (1 kHz < f < 8 kHz). The electrondensity distributions used for the ray-tracing calculations are derived frommeasurements with the Whisper relaxation sounder instrument. Our new resultsindicate that whistlers are observed outside the plasmasphere in the low-density regionsonly in the presence of large-scale irregularities within which the waves are ‘‘ducted.’’This conclusion is sustained by an exhaustive search of whistlers outside theplasmasphere using all the Cluster passes during 2001 and 2002. In all the cases wefound that dispersion characteristics are matched by ray-tracing simulations only if thewhistlers are ducted. In some cases, whistler wave energy injected by an individuallightning discharge appears with significant smearing in time. The new resultspresented in this paper support a possible explanation of why whistlers outside theplasmasphere are rarely observed, based on wave conversion electromagnetic whistlermode to quasi-electrostatic lower hybrid mode (Bell et al., 2004).
Published: 2005
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30. Equatorial electron density measurements in Saturn's inner magnetosphere

Author: J. B. Groene, M. K. Dougherty, D. A. Gurnett, P. Canu, George Hospodarsky, William S. Kurth, A. M. Persoon, Department of Physics and Astronomy [Ames, Iowa], Iowa State University (ISU), Centre d'étude des environnements terrestre et planétaires (CETP), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Space and Atmospheric Physics Group [London], Blackett Laboratory, Imperial College London-Imperial College London, and NASA through JPL contract 959515.
Subjects: Physics, Electron density, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], 010504 meteorology & atmospheric sciences, Waves in plasmas, Resonance, Magnetosphere, Plasma, Electron, 01 natural sciences, [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Geophysics, 13. Climate action, Saturn, Physics::Space Physics, 0103 physical sciences, Orbit (dynamics), General Earth and Planetary Sciences, Astrophysics::Earth and Planetary Astrophysics, Atomic physics, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences
Abstract: International audience; Upper hybrid resonance emissions detected by theRadio and Plasma Wave Science (RPWS) instrument on theCassini spacecraft are used to obtain electron densities onfive equatorial orbits of Saturn at radial distances rangingfrom 3 to 9 saturnian radii (RS). The electron density profilesfor these orbits show a highly repeatable radial dependencebeyond 5 RS, decreasing with increasing radial distanceapproximately as (1/R)3.63. Inside 5 RS, the electron densityprofiles are highly variable. We show that these radialvariations are consistent with a centrifugally-drivenoutward transport of plasma from a source inside 5 RS.
Published: 2005
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31. The inner magnetosphere of Saturn: Cassini RPWS cold plasmaresults from the first encounter

Author: Michiko Morooka, Reine Gill, P. Canu, Michael D. Desch, Mats André, D. A. Gurnett, George Hospodarsky, Anders Eriksson, Arne Pedersen, William S. Kurth, Jan-Erik Wahlund, Rolf Boström, T. F. Averkamp, A. M. Persoon, Georg Gustafsson, Swedish Institute of Space Physics [Uppsala] (IRF), Department of Physics and Astronomy [Iowa City], University of Iowa [Iowa City], Centre d'étude des environnements terrestre et planétaires (CETP), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Department of Physics [Oslo], Faculty of Mathematics and Natural Sciences [Oslo], University of Oslo (UiO)-University of Oslo (UiO), NASA Goddard Space Flight Center (GSFC), Swedish National Space Board (SNSB), and Swedish National Space Board
Subjects: Physics, Dusty plasma, 010504 meteorology & atmospheric sciences, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Waves in plasmas, Astronomy, Magnetosphere, Plasma, 01 natural sciences, [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], symbols.namesake, Geophysics, Gas torus, 13. Climate action, Physics::Plasma Physics, Saturn, Magnetosphere of Saturn, 0103 physical sciences, Physics::Space Physics, symbols, General Earth and Planetary Sciences, Langmuir probe, Astrophysics::Earth and Planetary Astrophysics, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences
Abstract: International audience; We present new results from the inner magnetosphere of Saturn obtained by the Radio and Plasma Wave Science (RPWS) investigation onboard Cassini around the period of the Saturn orbit injection (July 1, 2004). Plasma wave electric field emissions, voltage sweeps by the Langmuir probe (LP) and radio sounder data were used to infer the cold plasma (
Published: 2005
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32. The Cassini Radio and Plasma Wave Investigation

Author: D. A. Gurnett, W. S. Kurth, D. L. Kirchner, G. B. Hospodarsky, T. F. Averkamp, P. Zarka, A. Lecacheux, R. Manning, A. Roux, P. Canu, N. Cornilleau-Wehrlin, P. Galopeau, A. Meyer, R. Boström, G. Gustafsson, J.-E. Wahlund, L. Åhlen, H. O. Rucker, H. P. Ladreiter, W. Macher, L. J. C. Woolliscroft, H. Alleyne, M. L. Kaiser, M. D. Desch, W. M. Farrell, C. C. Harvey, P. Louarn, P. J. Kellogg, K. Goetz, and A. Pedersen
Subjects: 010504 meteorology & atmospheric sciences, 0103 physical sciences, 010303 astronomy & astrophysics, 01 natural sciences, 0105 earth and related environmental sciences
Published: 2004
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33. Correction to ‘‘ULF wave identification in the magnetosheath: The k-filtering technique applied to Cluster II data’’

Author: P. Canu, Patrick Robert, Gérard Chanteur, L. Mellul, Nicole Cornilleau-Wehrlin, Fouad Sahraoui, Laurence Rezeau, Jean-Louis Pinçon, J. M. Bosqued, G. Belmont, André Balogh, Centre d'étude des environnements terrestre et planétaires (CETP), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Centre d'étude spatiale des rayonnements (CESR), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Space and Atmospheric Physics Group [London], Blackett Laboratory, Imperial College London-Imperial College London, Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées
Subjects: Atmospheric Science, 010504 meteorology & atmospheric sciences, High Energy Physics::Lattice, Soil Science, Aquatic Science, Oceanography, 01 natural sciences, [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Transformation matrix, Magnetosheath, Geochemistry and Petrology, Earth and Planetary Sciences (miscellaneous), Cluster (physics), 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, Physics, Ecology, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Frame (networking), Paleontology, Forestry, Geophysics, Identification (information), Space and Planetary Science, Algorithm
Abstract: There is an error in the matrix transformation from the GSE frame to the MFA (Magnetic Field-Aligned) one
Published: 2004
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34. ULF wave identification in the magnetosheath: The k-filtering technique applied to Cluster II data

Author: Nicole Cornilleau-Wehrlin, Fouad Sahraoui, Patrick Robert, Gérard Chanteur, Gérard Belmont, Laurence Rezeau, Jean-Louis Pinçon, Jean-Michel Bosqued, L. Mellul, P. Canu, André Balogh, Centre d'étude des environnements terrestre et planétaires (CETP), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de physique et chimie de l'environnement (LPCE), Université d'Orléans (UO)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre d'étude spatiale des rayonnements (CESR), Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, Budapest University of Technology and Economics [Budapest] (BME), Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)
Subjects: Atmospheric Science, 010504 meteorology & atmospheric sciences, Field (physics), [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Interplanetary Physics: MHD waves and turbulence, Soil Science, Aquatic Science, Oceanography, 01 natural sciences, Superposition principle, symbols.namesake, Magnetosheath, [PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], Geochemistry and Petrology, 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), Wave vector, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, Physics, Angular frequency, Ecology, Magnetic energy, Paleontology, Forestry, Radio Science: Waves in plasma, Magnetospheric Physics: Plasma waves and instabilities, Computational physics, Space Plasma Physics: Experimental and mathematical techniques, Geophysics, Classical mechanics, Earth's magnetic field, Space and Planetary Science, Physics::Space Physics, symbols, Magnetospheric Physics: Magnetosheath, Doppler effect
Abstract: International audience; The magnetic fluctuations in the magnetosheath are studied, thanks to Cluster II data. The k-filtering technique is applied to explore ULF magnetic fluctuations using STAFF (Spatio-Temporal Analysis of a Field Fluctuations) data. Based on multipoint measurements, the k-filtering technique allows, for the first time, to estimate the Magnetic Field Energy Distribution (MFED) in both the angular frequency and wave vector space. We show how the localisation of the magnetic energy in the (ω, k) domain can be used to identify the linear modes that can propagate in the magnetosheath. A comparison between k-filtering results and prediction of the linear theory is performed. For the frequencies examined the magnetic energy seems to be distributed over the low frequency modes: mirror, Alfvén, and slow modes. Estimation of Doppler shift shows that each frequency observed is the superposition of different frequencies in the plasma frame. This ``mixture of modes'' at a given observed frequency explains why the fluctuations are generally not observed to be polarized, as shown in previous studies. Some other implications on a weak turbulence approach of the magnetic fluctuations in the magnetosheath are discussed.
Published: 2003
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35. Early results from the Whisper instrument on Cluster: an overview

Author: P. M. E. Décréau, P. Fergeau, V. Krasnoselskikh, E. Le Guirriec, M. Lévêque, Ph. Martin, O. Randriamboarison, J. L. Rauch, F. X. Sené, H. C. Séran, J. G. Trotignon, P. Canu, N. Cornilleau, H. de Féraudy, H. Alleyne, K. Yearby, P. B. Mögensen, G. Gustafsson, M. André, D. C. Gurnett, F. Darrouzet, J. Lemaire, C. C. Harvey, P. Travnicek, Whisper experimenters (Table 1), Laboratoire de physique et chimie de l'environnement (LPCE), Université d'Orléans (UO)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre d'étude des environnements terrestre et planétaires (CETP), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), University of Sheffield [Sheffield], DSRI, I. R. F. U., University of Iowa [Iowa City], Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique (BIRA-IASB), Centre d'étude spatiale des rayonnements (CESR), Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, Czech Academy of Sciences [Prague] (CAS), Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)
Subjects: Atmospheric Science, Electron density, Drift velocity, 010504 meteorology & atmospheric sciences, Frequency band, Magnetosphere, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Plasma oscillation, 01 natural sciences, 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), lcsh:Science, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Remote sensing, Physics, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Spacecraft, business.industry, lcsh:QC801-809, Geology, Astronomy and Astrophysics, Space physics, lcsh:QC1-999, Depth sounding, lcsh:Geophysics. Cosmic physics, Space and Planetary Science, lcsh:Q, business, lcsh:Physics
Abstract: The Whisper instrument yields two data sets: (i) the electron density determined via the relaxation sounder, and (ii) the spectrum of natural plasma emissions in the frequency band 2–80 kHz. Both data sets allow for the three-dimensional exploration of the magnetosphere by the Cluster mission. The total electron density can be derived unambiguously by the sounder in most magnetospheric regions, provided it is in the range of 0.25 to 80 cm-3 . The natural emissions already observed by earlier spacecraft are fairly well measured by the Whisper instrument, thanks to the digital technology which largely overcomes the limited telemetry allocation. The natural emissions are usually related to the plasma frequency, as identified by the sounder, and the combination of an active sounding operation and a passive survey operation provides a time resolution for the total density determination of 2.2 s in normal telemetry mode and 0.3 s in burst mode telemetry, respectively. Recorded on board the four spacecraft, the Whisper density data set forms a reference for other techniques measuring the electron population. We give examples of Whisper density data used to derive the vector gradient, and estimate the drift velocity of density structures. Wave observations are also of crucial interest for studying small-scale structures, as demonstrated in an example in the fore-shock region. Early results from the Whisper instrument are very encouraging, and demonstrate that the four-point Cluster measurements indeed bring a unique and completely novel view of the regions explored.Key words. Space plasma physics (instruments and techniques; discontinuities, general or miscellaneous)
Published: 2001
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36. Identification of natural plasma emissions observed close to the plasmapause by the Cluster-Whisper relaxation sounder

Author: Jean-Louis Rauch, P. Fergeau, Keith H. Yearby, Ph. Martin, H. C. Seran, M. Lévêque, Jean-Gabriel Trotignon, P. Canu, H. Alleyne, E. Le Guirriec, Pierrette Décréau, F. X. Sené, Centre d'étude des environnements terrestre et planétaires (CETP), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de physique et chimie de l'environnement (LPCE), Université d'Orléans (UO)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), University of Sheffield [Sheffield], and EGU, Publication
Subjects: Atmospheric Science, 010504 meteorology & atmospheric sciences, Meteorology, Magnetosphere, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Plasmasphere, Plasma oscillation, 01 natural sciences, Spectral line, 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), lcsh:Science, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Physics, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, [SDU.OCEAN] Sciences of the Universe [physics]/Ocean, Atmosphere, lcsh:QC801-809, Resonance, Geology, Astronomy and Astrophysics, Plasma, lcsh:QC1-999, Computational physics, lcsh:Geophysics. Cosmic physics, Distribution function, Space and Planetary Science, Physics::Space Physics, [SDU.STU] Sciences of the Universe [physics]/Earth Sciences, Electron temperature, lcsh:Q, lcsh:Physics
Abstract: We use the data collected by the Whisper instrument onboard the Cluster spacecraft for a first test of its capabilities in the identification of the natural plasma waves observed in the Earth’s magnetosphere. The main signatures observed at the plasma frequency, upper hybrid frequency, and electron Bernstein modes were often difficult to be reliably recognized on previous missions. We use here the characteristic frequencies provided by the resonances triggered by the relaxation sounder of Whisper to identify with good confidence the various signatures detected in the complex wave spectra collected close to the plasmapause. Coupled with the good sensitivity, frequency and time resolution of Whisper, the resonances detected by the sounder allow one to precisely spot these natural emissions. This first analysis seems to confirm the interpretation of Geos observations: the natural emissions observed in Bernstein modes above the plasma frequency, now widely observed onboard Cluster, are not modeled by a single Maxwellian electrons distribution function. Therefore, multi-temperature electron distribution functions should be considered.Key words. Space plasma physics (active perturbation experiments; waves and instabilities; instrument and techniques)
Published: 2001

37. How to determine the thermal electron density and the magnetic field strength from the Cluster/Whisper observations around the Earth

Author: E. Le Guirriec, Pierrette Décréau, Ph. Martin, H. C. Seran, P. Canu, F. X. Sené, Jean-Louis Rauch, Keith H. Yearby, Orélien Randriamboarison, H. Alleyne, P. Fergeau, M. Lévêque, Vladimir Krasnoselskikh, Jean-Gabriel Trotignon, EGU, Publication, Laboratoire de physique et chimie de l'environnement (LPCE), Université d'Orléans (UO)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre d'étude des environnements terrestre et planétaires (CETP), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Department of Automatic Control and Systems Engineering [ Sheffield] (ACSE), and University of Sheffield [Sheffield]
Subjects: Atmospheric Science, Electron density, 010504 meteorology & atmospheric sciences, Population, Magnetosphere, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, 01 natural sciences, Optics, Electric field, 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), education, lcsh:Science, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Physics, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, education.field_of_study, business.industry, [SDU.OCEAN] Sciences of the Universe [physics]/Ocean, Atmosphere, lcsh:QC801-809, Geology, Astronomy and Astrophysics, Space physics, Plasma, lcsh:QC1-999, Magnetic field, Computational physics, lcsh:Geophysics. Cosmic physics, Distribution function, Space and Planetary Science, [SDU.STU] Sciences of the Universe [physics]/Earth Sciences, lcsh:Q, business, lcsh:Physics
Abstract: The Wave Experiment Consortium, WEC, is a highly integrated package of five instruments used to study the plasma environment around the Earth. One of these instruments, the Waves of HIgh frequency and Sounder for Probing of Electron density by Relaxation, Whisper, aims at the thermal electron density evaluation and natural wave monitoring in the 4–83 kHz frequency range. In its active working mode, which is our primarily concern here, the Whisper instrument transmits a short wave train at a swept frequency and receives echoes after a delay. Incidentally, it behaves like a classical ground-based ionosonde. Natural modes of oscillations may thus be excited in the surrounding medium. This means that with suitable interpretations, the Whisper sounding technique becomes a powerful tool for plasma diagnosis. By taking into account the characteristic frequencies of the magnetoplasmas encountered by the Cluster spacecraft, it is indeed possible to reliably and accurately determine the electron density and, to a lesser degree, the magnetic field strength from the Whisper electric field measurements. Due to the predominantly electrostatic nature of the waves that are excited, observations of resonances may also lead to information on the electron velocity distribution functions. The existence of a hot population may indeed be revealed and the hot to cold density ratio can be estimated.Key words. Magnetospheric physics (plasma waves and instabilities). Space plasma physics (active perturbation experiments; instruments and techniques)
Published: 2001

38. ULF waves in the Io torus: ULYSSES observations

Author: Naiguo Lin, Robert J. MacDowall, André Balogh, Paul J. Kellogg, P. Canu, Nicole Cornilleau-Wehrlin, C. de Villedary, R. J. Forsyth, Y. Mei, Laurence Rezeau, University of Minnesota [Twin Cities] (UMN), University of Minnesota System, School of Physics and Astronomy [Minneapolis], University of Minnesota System-University of Minnesota System, NASA Goddard Space Flight Center (GSFC), Centre d'étude des environnements terrestre et planétaires (CETP), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Blackett Laboratory, and Imperial College London
Subjects: Atmospheric Science, 010504 meteorology & atmospheric sciences, Whistler, Equator, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Astrophysics, ULYSSES MISSION, Oceanography, 01 natural sciences, TORUSES, WAVE DISPERSION, [PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], Dispersion relation, Earth and Planetary Sciences (miscellaneous), MATHEMATICAL MODELS, 010303 astronomy & astrophysics, Water Science and Technology, Physics, Ecology, ENERGETIC PARTICLES, Forestry, Polarization (waves), Geophysics, ASTRONOMICAL MODELS, Poynting vector, Physics::Space Physics, POLARIZATION (WAVES), EXTREMELY LOW FREQUENCIES, TOROIDAL PLASMAS, Radio wave, SPACEBORNE ASTRONOMY, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Soil Science, Aquatic Science, Electromagnetic radiation, SPACE PLASMAS, Geochemistry and Petrology, ION SCATTERING, 0103 physical sciences, Pitch angle, WHISTLERS, RADIO WAVES, 0105 earth and related environmental sciences, Earth-Surface Processes, Paleontology, ION CYCLOTRON RADIATION, IO, Computational physics, 13. Climate action, Space and Planetary Science
Abstract: International audience; Throughout the Io torus, Ulysses has observed intense ultralow frequency (ULF) wave activity in both electric and magnetic components. Such ULF waves have been previously suggested as the source of ion precipitation leading to Jovian aurorae. The peaks of the wave spectra are closely related to the ion cyclotron frequencies, which is evidence of the waves being ion cyclotron waves (ICWs). Analysis of the dispersion relation using a multicomponent density model shows that at high latitudes (approximately 30 deg), peak frequencies of the waves fall into L mode branches of guided or unguided ICWs. Near the equator, in addition to the ICWs below fcO(2+), there are strong signals at approximately 10 Hz which require an unexpectedly large energetic ion temperature anistropy to be explained by the excitation of either convective or nonconvective ion cyclotron instabilities. Their generation mechanism remains open for the future study. Evaluation of the Poynting vector and the dispersion relation analysis suggest that the waves near the equator had a small wave angle relative to the magnetic field, while those observed at high latitudes were more oblique. The polarization of the waves below fcH(+) is more random than that of the whistler mode waves, but left-hand-polarized components of the waves can still be seen. The intensity of the ICWs both near the equator and at high latitudes are strong enough to meet the requirement for producing strong pitch angle scattering of energetic ions.
Published: 1993
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39. Alfvén waves in the near-PSBL lobe: Cluster observations

Author: T. Takada, R. Nakamura, W. Baumjohann, K. Seki, Z. Vörös, Y. Asano, M. Volwerk, A. Runov, T. L. Zhang, A. Balogh, G. Paschmann, R. B. Torbert, B. Klecker, H. Rème, P. Puhl-Quinn, P. Canu, P. M. E. Décréau, Space Research Institute of Austrian Academy of Sciences (IWF), Austrian Academy of Sciences (OeAW), Solar-Terrestrial Environment Laboratory [Nagoya] (STEL), Nagoya University, Max-Planck-Institut für Extraterrestrische Physik (MPE), Imperial College London, University of New Hampshire (UNH), Centre d'étude spatiale des rayonnements (CESR), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Centre d'étude des environnements terrestre et planétaires (CETP), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées
Subjects: Atmospheric Science, 010504 meteorology & atmospheric sciences, Field line, Electrojet, 7. Clean energy, 01 natural sciences, Instability, Alfvén wave, [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Two-stream instability, Physics::Plasma Physics, 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), lcsh:Science, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Physics, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], lcsh:QC801-809, Plasma sheet, Geology, Astronomy and Astrophysics, Geophysics, Ion acoustic wave, lcsh:QC1-999, Computational physics, lcsh:Geophysics. Cosmic physics, 13. Climate action, Space and Planetary Science, Poynting vector, Physics::Space Physics, lcsh:Q, lcsh:Physics
Abstract: Electromagnetic low-frequency waves in the magnetotail lobe close to the PSBL (Plasma Sheet Boundary Layer) are studied using the Cluster spacecraft. The lobe waves show Alfvénic properties and transport their wave energy (Poynting flux) on average toward the Earth along magnetic field lines. Most of the wave events are rich with oxygen (O+) ion plasma. The rich O+ plasma can serve to enhance the magnetic field fluctuations, resulting in a greater likelihood of observation, but it does not appear to be necessary for the generation of the waves. Taking into account the fact that all events are associated with auroral electrojet enhancements, the source of the lobe waves might be a substorm-associated instability, i.e. some instability near the reconnection site, or an ion beam-related instability in the PSBL.
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40. Radio and Plasma Wave Observations at Saturn from Cassini s Approach and First Orbit

Author: T. F. Averkamp, Michael D. Desch, William M. Farrell, H. Alleyne, Philippe Louarn, William S. Kurth, Georg Fischer, M. L. Kaiser, Aurélien Roux, H. P. Ladreiter, Jan-Erik Wahlund, Baptiste Cecconi, P. Zarka, D. A. Gurnett, Helmut O. Rucker, Georg Gustafsson, Arne Pedersen, Alain Lecacheux, George Hospodarsky, Paul J. Kellogg, P. Canu, Nicole Cornilleau-Wehrlin, Patrick H. M. Galopeau, Rolf Boström, A. M. Persoon, Keith Goetz, C. C. Harvey, Department of Physics and Astronomy [Iowa City], University of Iowa [Iowa City], Observatoire de Paris - Site de Paris (OP), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Centre d'étude des environnements terrestre et planétaires (CETP), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre d'étude spatiale des rayonnements (CESR), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), Department of Physics and Astronomy, Iowa State University, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Physique des plasmas, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Observatoire de Paris, Université Paris sciences et lettres (PSL), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Swedish Institute of Space Physics, NASA/Goddard Space Flight Center (NASA/GSFC), Department of Physics and Astronomy, University of Minnesota, Institut für Weltraumforschung, Österreichische Akademie der Wissenschaften (IWF), Department of Automatic Control and System Engineering, University of Oslo (UiO), Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, Swedish Institute of Space Physics [Uppsala] (IRF), NASA Goddard Space Flight Center (GSFC), School of Physics and Astronomy [Minneapolis], University of Minnesota [Twin Cities] (UMN), University of Minnesota System-University of Minnesota System, Space Research Institute of Austrian Academy of Sciences (IWF), Austrian Academy of Sciences (OeAW), Department of Automatic Control and Systems Engineering [ Sheffield] (ACSE), University of Sheffield [Sheffield], Department of Physics [Oslo], Faculty of Mathematics and Natural Sciences [Oslo], and University of Oslo (UiO)-University of Oslo (UiO)
Subjects: Physics, Rotation period, Hiss, Multidisciplinary, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], 010504 meteorology & atmospheric sciences, Whistler, Rings of Saturn, Astronomy, Magnetosphere, 01 natural sciences, [PHYS.PHYS.PHYS-SPACE-PH]Physics [physics]/Physics [physics]/Space Physics [physics.space-ph], [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], [PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], 13. Climate action, Saturn, Magnetosphere of Saturn, 0103 physical sciences, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Radio wave
Abstract: International audience; We report data from the Cassini radio and plasma wave instrument during the approach and first orbit at Saturn. During the approach, radio emissions from Saturn showed that the radio rotation period is now 10 hours 45 minutes 45 +/- 36 seconds, about 6 minutes longer than measured by Voyager in 1980 to 1981. In addition, many intense impulsive radio signals were detected from Saturn lightning during the approach and first orbit. Some of these have been linked to storm systems observed by the Cassini imaging instrument. Within the magnetosphere, whistler-mode auroral hiss emissions were observed near the rings, suggesting that a strong electrodynamic interaction is occurring in or near the rings.
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41. Possible role of electromagnetic low frequency waves in the Io torus in the production of Jovian aurorae

Author: P. Canu, G. Belmont, André Balogh, Laurence Rezeau, R. J. Forsyth, Nicole Cornilleau-Wehrlin, R. Prange, Centre d'étude des environnements terrestre et planétaires (CETP), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut d'astrophysique spatiale (IAS), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Sud - Paris 11 (UP11), Blackett Laboratory, Imperial College London, and Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Physics, 010504 meteorology & atmospheric sciences, [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Field line, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Astronomy, Magnetic dip, Astronomy and Astrophysics, Torus, 01 natural sciences, Jovian, Physics::Geophysics, Magnetic field, Latitude, Jupiter, [PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], 13. Climate action, Space and Planetary Science, Physics::Space Physics, 0103 physical sciences, Astrophysics::Earth and Planetary Astrophysics, Longitude, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences
Abstract: International audience; The possible role of ULF waves observed in the Io torus in the generation of Jovian aurorae is investigated. Auroral emissions have been observed, not only at high latitude, but also at the footprint of magnetic field lines connected to the Io torus in a limited longitudinal range around 150°. As Ulysses passed by Jupiter, it explored the Io torus in latitude and longitude, allowing to test a possible localization of the waves on field lines mapping down into the aurora. A maximum intensity of the waves is observed in the high latitude part of the torus around the longitude where the aurorae were observed. Another maximum is also observed at the magnetic equator. The propagation mode of the waves is discussed and their amplitude is compared to the values necessary for scattering ions, showing that the ULF waves could possibly be at the origin of the aurorae.
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