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1. Double cusp encounter by Cluster: double cusp or motion of the cusp?

Author

C. P. Escoubet, J. Berchem, K. J. Trattner, F. Pitout, R. Richard, M. G. G. T. Taylor, J. Soucek, B. Grison, H. Laakso, A. Masson, M. Dunlop, I. Dandouras, H. Reme, A. Fazakerley, and P. Daly

Subjects
Science, Physics, QC1-999, Geophysics. Cosmic physics, QC801-809
Abstract

Modelling plasma entry in the polar cusp has been successful in reproducing ion dispersions observed in the cusp at low and mid-altitudes. The use of a realistic convection pattern, when the IMF-By is large and stable, allowed Wing et al. (2001) to predict double cusp signatures that were subsequently observed by the DMSP spacecraft. In this paper we present a cusp crossing where two cusp populations are observed, separated by a gap around 1° Invariant Latitude (ILAT) wide. Cluster 1 (C1) and Cluster 2 (C2) observed these two cusp populations with a time delay of 3 min, and about 15 and 42 min later Cluster 4 (C4) and Cluster 3 (C3) observed, respectively, a single cusp population. A peculiarity of this event is the fact that the second cusp population seen on C1 and C2 was observed at the same time as the first cusp population on C4. This would tend to suggest that the two cusp populations had spatial features similar to the double cusp. Due to the nested crossing of C1 and C2 through the gap between the two cusp populations, C2 being first to leave the cusp and last to re-enter it, these observations are difficult to be explained by two distinct cusps with a gap in between. However, since we observe the cusp in a narrow area of local time post-noon, a second cusp may have been present in the pre-noon sector but could not be observed. On the other hand, these observations are in agreement with a motion of the cusp first dawnward and then back duskward due to the effect of the IMF-By component.

Published
2013
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2. Overlapping ion structures in the mid-altitude cusp under northward IMF: signature of dual lobe reconnection?

Author

F. Pitout, C. P. Escoubet, M. G. G. T. Taylor, J. Berchem, and A. P. Walsh

Subjects
Science, Physics, QC1-999, Geophysics. Cosmic physics, QC801-809
Abstract

On some rare occasions, data from the Cluster Ion Spectrometer (CIS) in the mid-altitude cusp reveal overlapping ion populations under northward interplanetary magnetic field (IMF). While the poleward part of the cusp exhibits the expected reverse dispersion due to lobe reconnection, its equatorward part shows a second ion population at higher-energy that coexists with the low energy tail of the dispersion. This second population is either dispersionless or slightly dispersed with energies increasing with increasing latitudes, indicative of lobe reconnection as well. Our analysis of a case that occurred 3 September 2002 when the IMF stayed northward for more than two hours suggests that the second population comes from the opposite hemisphere and is very likely on newly-closed field lines. We interpret this overlap of cusp populations as a clear mid-altitude signature of re-closed magnetic field lines by double lobe reconnection (reconnection in both hemispheres) under northward IMF. This interpretation is supported by modelling performed with the Cooling model and an MHD model.

Published
2012
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3. Polarisation in the auroral red line during coordinated EISCAT Svalbard Radar/optical experiments

Author

M. Barthélémy, J. Lilensten, F. Pitout, C. Simon Wedlund, R. Thissen, D. Lorentzen, F. Sigernes, J. Moen, G. Gronoff, I. McCrea, H. Rothkael, H. Ménager, and A. Aruliah

Subjects
Science, Physics, QC1-999, Geophysics. Cosmic physics, QC801-809
Abstract

The polarisation of the atomic oxygen red line in the Earth's thermosphere is observed in different configurations with respect to the magnetic field line at high latitude during several coordinated Incoherent Scatter radar/optical experiment campaigns. When pointing northward with a line-of-sight nearly perpendicular to the magnetic field, we show that, as expected, the polarisation is due to precipitated electrons with characteristic energies of a few hundreds of electron Volts. When pointing toward the zenith or southward with a line-of-sight more parallel to the magnetic field, we show that the polarisation practically disappears. This confirms experimentally the predictions deduced from the recent discovery of the red line polarisation. We show that the polarisation direction is parallel to the magnetic field line during geomagnetic activity intensification and that these results are in agreement with theoretical work.

Published
2011
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4. Cusp observations during a sequence of fast IMF BZ reversals

Author

H. T. Cai, I. W. McCrea, M. W. Dunlop, J. A. Davies, Y. V. Bogdanova, F. Pitout, S. E. Milan, M. Lockwood, and S. Y. Ma

Subjects
Science, Physics, QC1-999, Geophysics. Cosmic physics, QC801-809
Abstract

In recent years, a large number of papers have reported the response of the cusp to solar wind variations under conditions of northward or southward Interplanetary Magnetic Field (IMF) Z-component (BZ). These studies have shown the importance of both temporal and spatial factors in determining the extent and morphology of the cusp and the changes in its location, connected to variations in the reconnection geometry. Here we present a comparative study of the cusp, focusing on an interval characterised by a series of rapid reversals in the BZ-dominated IMF, based on observations from space-borne and ground-based instrumentation. During this interval, from 08:00 to 12:00 UT on 12 February 2003, the IMF BZ component underwent four reversals, remaining for around 30 min in each orientation. The Cluster spacecraft were, at the time, on an outbound trajectory through the Northern Hemisphere magnetosphere, whilst the mainland VHF and Svalbard (ESR) radars of the EISCAT facility were operating in support of the Cluster mission. Both Cluster and the EISCAT were, on occasion during the interval, observing the cusp region. The series of IMF reversals resulted in a sequence of poleward and equatorward motions of the cusp; consequently Cluster crossed the high-altitude cusp twice before finally exiting the dayside magnetopause, both times under conditions of northward IMF BZ. The first magnetospheric cusp encounter, by all four Cluster spacecraft, showed reverse ion dispersion typical of lobe reconnection; subsequently, Cluster spacecraft 1 and 3 (only) crossed the cusp for a second time. We suggest that, during this second cusp crossing, these two spacecraft were likely to have been on newly closed field lines, which were first reconnected (opened) at low latitudes and later reconnected again (re-closed) poleward of the northern cusp. At ionospheric altitudes, the latitudinal excursions of the cusp/cleft region in response to the series of the IMF polarity changes were clearly captured by both the ESR and the Pykkvibaer radar of the SuperDARN HF network. The Open-Closed field-line Boundary (OCB) inferred from the HF radar observations underwent latitudinal variations in response to the IMF polarity changes that are in accordance with those predicted by Newell et al. (1989). Furthermore, variations in the ionospheric parameters yielded by the EISCAT VHF and ESR radars are basically consistent with inferences drawn from the HF radar observations. We conclude that Cluster spacecraft 1 and 3 crossed the cusp for a second time as a result of the latitudinal migration of the cusp in response to the IMF polarity reversals; at that time, however, the cusp lay poleward of spacecraft 4. Snapshots of the cusp from two DMSP satellite passes provide further support for this interpretation.

Published
2009
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5. Cluster survey of the mid-altitude cusp – Part 2: Large-scale morphology

Author

F. Pitout, C. P. Escoubet, B. Klecker, and I. Dandouras

Subjects
Science, Physics, QC1-999, Geophysics. Cosmic physics, QC801-809
Abstract

In this second part of our statistical study of the mid-altitude cusp, we compare the cusp morphology, as seen in the Cluster ion spectrometer (CIS), to the interplanetary magnetic field (IMF) orientation. We first recall the method we have used a) to define the cusp properties, b) to sort IMF conditions or behaviour in classes, c) to determine the proper time delay between the solar wind monitors and Cluster. Then, we define a few morphological features of the cusp and we relate these to the prevailing IMF. Our results reveal, among other things, that the occurrence of clearly dispersed ion structures in the cusp is 48%. From these dispersions, we infer the distance to reconnection site, which we relate to external conditions. In all other cases, the cusp exhibits a more disturbed behaviour in terms of ion structures and fall in our "discontinuous" or "irregular" categories. Among these, a few interesting cases of discontinuous cusps occurring under stable IMF conditions have been identified. They all occur when the IMF is dominated by its Y-component, which plays in principle in favour of anti-parallel reconnection but their wide MLT and latitudinal distributions is a priori incompatible with the anti-parallel reconnection hypothesis solely.

Published
2009
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6. Shape, size, velocity and field-aligned currents of dayside plasma injections: a multi-altitude study

Author

A. Marchaudon, J.-C. Cerisier, M. W. Dunlop, F. Pitout, J.-M. Bosqued, and A. N. Fazakerley

Subjects
Science, Physics, QC1-999, Geophysics. Cosmic physics, QC801-809
Abstract

On 20 February 2005, Cluster in the outer magnetosphere and Double Star-2 (TC-2) at mid-altitude are situated in the vicinity of the northern cusp/mantle, with Cluster moving sunward and TC-2 anti-sunward. Their magnetic footprints come very close together at about 15:28 UT, over the common field-of-view of SuperDARN radars. Thanks to this conjunction, we determine the velocity, the transverse sizes, perpendicular and parallel to this velocity, and the shape of three magnetic flux tubes of magnetosheath plasma injection. The velocity of the structures determined from the Cluster four-spacecraft timing analysis is almost purely antisunward, in contrast with the antisunward and duskward convection velocity inside the flux tubes. The transverse sizes are defined from the Cluster-TC-2 separation perpendicular to the magnetic field, and from the time spent by a Cluster spacecraft in one structure; they are comprised between 0.6 and 2 RE in agreement with previous studies. Finally, using a comparison between the eigenvectors deduced from a variance analysis of the magnetic perturbation at the four Cluster and at TC-2, we show that the upstream side of the injection flux tubes is magnetically well defined, with even a concave front for the third one giving a bean-like shape, whereas the downstream side is far more turbulent. We also realise the first quantitative comparison between field-aligned currents at Cluster calculated with the curlometer technique and with the single-spacecraft method, assuming infinite parallel current sheets and taking into account the velocity of the injection flux tubes. The results agree nicely, confirming the validity of both methods. Finally, we compare the field-aligned current distribution of the three injection flux tubes at the altitudes of Cluster and TC-2. Both profiles are fairly similar, with mainly a pair of opposite field-aligned currents, upward at low-latitude and downward at high-latitude. In terms of intensity, the field-aligned currents at Cluster are two to three times less intense than at TC-2 for the first two flux tubes, in agreement with magnetic field line convergence. For the third flux tube, the intensity is equal, which is explained by the fact that TC-2 crosses the tube on its edge. Finally, the analysis of the ion and electron moments at Cluster shows that the field-aligned currents result from a small difference between upward ion and electron fluxes.

Published
2009
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7. Cluster observations of a field aligned current at the dawn flank of a bursty bulk flow

Author

K. Snekvik, S. Haaland, N. Østgaard, H. Hasegawa, R. Nakamura, T. Takada, L. Juusola, O. Amm, F. Pitout, H. Rème, B. Klecker, and E. A. Lucek

Subjects
Science, Physics, QC1-999, Geophysics. Cosmic physics, QC801-809
Abstract

This article describes observations of a bursty bulk flow (BBF) in the outer central plasma sheet. The observations are made with the Cluster satellites, located approximately 19 RE downtail, close to the midnight sector in the Southern Hemisphere. 40–60 s after Cluster first detected the BBF, there was a large bipolar perturbation in the magnetic field. A Grad-Shafranov reconstruction has revealed that this is created by a field-aligned current at the flank of the BBF. Further analysis of the plasma moments has shown that the BBF has the properties of a depleted flux tube. Depleted flux tubes are an important theoretical model for how plasma and magnetic flux can be transported Earthward in the magnetotail as part of the Dungey cycle. The field aligned current is directed Earthward and is located at the dawn side of the BBF. Thus, it is consistent with the magnetic shear at the flank of an Earthward moving BBF. The total current has been estimated to be about 0.1 MA.

Published
2007
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8. Cluster survey of the mid-altitude cusp: 1. size, location, and dynamics

Author

F. Pitout, C. P. Escoubet, B. Klecker, and H. Rème

Subjects
Science, Physics, QC1-999, Geophysics. Cosmic physics, QC801-809
Abstract

We present a statistical study of four years of Cluster crossings of the mid-altitude cusp. In this first part of the study, we start by introducing the method we have used a) to define the cusp properties, b) to sort the interplanetary magnetic field (IMF) conditions or behaviors into classes, c) to determine the proper time delay between the solar wind monitors and Cluster. Out of the 920 passes that we have analyzed, only 261 fulfill our criteria and are considered as cusp crossings. We look at the size, location and dynamics of the mid-altitude cusp under various IMF orientations and solar wind conditions. For southward IMF, Bz rules the latitudinal dynamics, whereas By governs the zonal dynamics, confirming previous works. We show that when |By| is larger than |Bz|, the cusp widens and its location decorrelates from By. We interpret this feature in terms of component reconnection occurring under By-dominated IMF. For northward IMF, we demonstrate that the location of the cusp depends primarily upon the solar wind dynamic pressure and upon the Y-component of the IMF. Also, the multipoint capability of Cluster allows us to conclude that the cusp needs typically more than ~20 min to fully adjust its location and size in response to changes in external conditions, and its speed is correlated to variations in the amplitude of IMF-Bz. Indeed, the velocity in °ILAT/min of the cusp appears to be proportional to the variation in Bz in nT: Vcusp=0.024 ΔBz. Finally, we observe differences in the behavior of the cusp in the two hemispheres. Those differences suggest that the cusp moves and widens more freely in the summer hemisphere.

Published
2006
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9. Coordinated Cluster/Double Star observations of dayside reconnection signatures

Author

M. W. Dunlop, M. G. G. T. Taylor, J. A. Davies, C. J. Owen, F. Pitout, A. N. Fazakerley, Z. Pu, H. Laakso, Y. V. Bogdanova, Q.-G. Zong, C. Shen, K. Nykyri, B. Lavraud, S. E. Milan, T. D. Phan, H. Rème, C. P. Escoubet, C. M. Carr, P. Cargill, M. Lockwood, and B. Sonnerup

Subjects
Science, Physics, QC1-999, Geophysics. Cosmic physics, QC801-809
Abstract

The recent launch of the equatorial spacecraft of the Double Star mission, TC-1, has provided an unprecedented opportunity to monitor the southern hemisphere dayside magnetopause boundary layer in conjunction with northern hemisphere observations by the quartet of Cluster spacecraft. We present first results of one such situation where, on 6 April 2004, both Cluster and the Double Star TC-1 spacecraft were on outbound transits through the dawnside magnetosphere. The observations are consistent with ongoing reconnection on the dayside magnetopause, resulting in a series of flux transfer events (FTEs) seen both at Cluster and TC-1, which appear to lie north and south of the reconnection line, respectively. In fact, the observed polarity and motion of each FTE signature advocates the existence of an active reconnection region consistently located between the positions of Cluster and TC-1, with Cluster observing northward moving FTEs with +/- polarity, whereas TC-1 sees -/+ polarity FTEs. This assertion is further supported by the application of a model designed to track flux tube motion for the prevailing interplanetary conditions. The results from this model show, in addition, that the low-latitude FTE dynamics are sensitive to changes in convected upstream conditions. In particular, changing the interplanetary magnetic field (IMF) clock angle in the model suggests that TC-1 should miss the resulting FTEs more often than Cluster and this is borne out by the observations.

Published
2005
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10. Ionospheric plasma density structures associated with magnetopause motion: a case study using the Cluster spacecraft and the EISCAT Svalbard Radar

Author

F. Pitout, C. P. Escoubet, and E. A. Lucek

Subjects
Science, Physics, QC1-999, Geophysics. Cosmic physics, QC801-809
Abstract

On 5 January 2003, the footprint of the Cluster spacecraft, then orbiting in the dayside magnetosphere near the magnetopause, was in the close vicinity of the EISCAT Svalbard Radar (ESR) in the dayside afternoon sector. This configuration made possible the study of the magnetopause motion and its direct consequences on the ionospheric plasma at high latitude. Cluster observed multiple magnetopause crossings despite its high latitude, while on the ground the magnetic activity was very low, whereas the ionospheric plasma sounded by the ESR exhibited poleward moving plasma density structures. In this paper, we compare the satellite and radar data, in order to show that the plasma density structures are directly related to the magnetopause motion and its associated pulsed ionospheric flow. We propose that the variations in electric field make the convection velocity vary enough to alter the electron population by accelerating the chemistry in the F-region and act as a source of electron depletion. The magnetopause motion is in this case, a source of plasma density structures in the polar dayside ionosphere.

Published
2004
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11. High-latitude dayside ionosphere response to Pc5 field line resonance

Author

F. Pitout, P. Eglitis, and P.-L. Blelly

Subjects
Science, Physics, QC1-999, Geophysics. Cosmic physics, QC801-809
Abstract

We report observations of pulsations due to Field Line Resonance (FLR) in the morning sector of the high-latitude dayside ionosphere on 1 February 1998. The Geotail spacecraft, ideally skimming the dayside magnetopause, monitored the magnetopause motion, which is seen to induce a modulated response of the ionosphere by means of ULF waves. Pulsations in the Pc5 frequency range were observed in the ground magnetic field measured by the IMAGE array, as well as in the electron and ion temperatures measured by the EISCAT Svalbard Radar. The ion temperature oscillations are an indicator of a modulated convection electric field while field-aligned currents (FAC) associated with the FLR control the electron temperature. We have performed a simulation of the ionosphere experiencing sinusoidal FAC and electric field in order to confirm our hypothesis. In addition to the ionospheric response, the possible cause of the FLR and processes involved are also discussed.Key words. Magnetospheric physics (MHD waves and instabilities; magnetosphere-ionosphere interactions) – Ionosphere (polar ionosphere)

Published
2003
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12. Simultaneous high- and low-latitude reconnection: ESR and DMSP observations

Author

F. Pitout, P. T. Newell, and S. C. Buchert

Subjects
Science, Physics, QC1-999, Geophysics. Cosmic physics, QC801-809
Abstract

We present EISCAT Svalbard Radar and DMSP observations of a double cusp during an interval of predominantly northward IMF on 26 November 2000. In the cusp region, the ESR dish, pointing northward, recorded sun-ward ionospheric flow at high latitudes (above 82° GL), indicating reconnection occuring in the magnetospheric lobe. Meanwhile, the same dish also recorded bursts of poleward flow, indicative of bursty reconnection at the subsolar magnetopause. Within this time interval, the DMSP F13 satellite passed in the close vicinity of the Svalbard archipelago. The particle measurement on board exhibited a double cusp structure in which two oppositely oriented ion dispersions are recorded. We interpret this set of data in terms of simultaneous merging at low- and high-latitude magnetopause. We discuss the conditions for which such simultaneous high-latitude and low-latitude reconnection can be anticipated. We also discuss the consequences of the presence of two X-lines in the dayside polar ionosphere.Key words. Magnetospheric physics (solar wind-magnetosphere interactions) – Ionosphere (polar ionosphere; plasma convection)

Published
2002
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13. Coordinated Cluster and ground-based instrument observations of transient changes in the magnetopause boundary layer during an interval of predominantly northward IMF: relation to reconnection pulses and FTE signatures

Author

M. Lockwood, A. Fazakerley, H. Opgenoorth, J. Moen, A. P. van Eyken, M. Dunlop, J.-M. Bosqued, G. Lu, C. Cully, P. Eglitis, I. W. McCrea, M. A. Hapgood, M. N. Wild, R. Stamper, W. Denig, M. Taylor, J. A. Wild, G. Provan, O. Amm, K. Kauristie, T. Pulkkinen, A. Strømme, P. Prikryl, F. Pitout, A. Balogh, H. Rème, R. Behlke, T. Hansen, R. Greenwald, H. Frey, S. K. Morley, D. Alcaydé, P.-L. Blelly, E. Donovan, M. Engebretson, M. Lester, J. Watermann, and M. F. Marcucci

Subjects
Science, Physics, QC1-999, Geophysics. Cosmic physics, QC801-809
Abstract

We study a series of transient entries into the low-latitude boundary layer (LLBL) of all four Cluster spacecraft during an outbound pass through the mid-afternoon magnetopause ( [ XGSM, YGSM, ZGSM ] ≈ [ 2, 7, 9 ] RE). The events take place during an interval of northward IMF, as seen in the data from the ACE satellite and lagged by a propagation delay of 75 min that is welldefined by two separate studies: (1) the magnetospheric variations prior to the northward turning (Lockwood et al., 2001, this issue) and (2) the field clock angle seen by Cluster after it had emerged into the magnetosheath (Opgenoorth et al., 2001, this issue). With an additional lag of 16.5 min, the transient LLBL events correlate well with swings of the IMF clock angle (in GSM) to near 90°. Most of this additional lag is explained by ground-based observations, which reveal signatures of transient reconnection in the pre-noon sector that then take 10–15 min to propagate eastward to 15 MLT, where they are observed by Cluster. The eastward phase speed of these signatures agrees very well with the motion deduced by the cross-correlation of the signatures seen on the four Cluster spacecraft. The evidence that these events are reconnection pulses includes: transient erosion of the noon 630 nm (cusp/cleft) aurora to lower latitudes; transient and travelling enhancements of the flow into the polar cap, imaged by the AMIE technique; and poleward-moving events moving into the polar cap, seen by the EISCAT Svalbard Radar (ESR). A pass of the DMSP-F15 satellite reveals that the open field lines near noon have been opened for some time: the more recently opened field lines were found closer to dusk where the flow transient and the poleward-moving event intersected the satellite pass. The events at Cluster have ion and electron characteristics predicted and observed by Lockwood and Hapgood (1998) for a Flux Transfer Event (FTE), with allowance for magnetospheric ion reflection at Alfvénic disturbances in the magnetopause reconnection layer. Like FTEs, the events are about 1 RE in their direction of motion and show a rise in the magnetic field strength, but unlike FTEs, in general, they show no pressure excess in their core and hence, no characteristic bipolar signature in the boundary-normal component. However, most of the events were observed when the magnetic field was southward, i.e. on the edge of the interior magnetic cusp, or when the field was parallel to the magnetic equatorial plane. Only when the satellite begins to emerge from the exterior boundary (when the field was northward), do the events start to show a pressure excess in their core and the consequent bipolar signature. We identify the events as the first observations of FTEs at middle altitudes.Key words. Magnetospheric physics (magnetopause, cusp and boundary layers; magnetosphere-ionosphere interactions; solar wind-magnetosphere interactions)

Published
2001
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14. Coordinated Cluster, ground-based instrumentation and low-altitude satellite observations of transient poleward-moving events in the ionosphere and in the tail lobe

Author

M. Lockwood, H. Opgenoorth, A. P. van Eyken, A. Fazakerley, J.-M. Bosqued, W. Denig, J. A. Wild, C. Cully, R. Greenwald, G. Lu, O. Amm, H. Frey, A. Strømme, P. Prikryl, M. A. Hapgood, M. N. Wild, R. Stamper, M. Taylor, I. McCrea, K. Kauristie, T. Pulkkinen, F. Pitout, A. Balogh, M. Dunlop, H. Rème, R. Behlke, T. Hansen, G. Provan, P. Eglitis, S. K. Morley, D. Alcaydé, P.-L. Blelly, J. Moen, E. Donovan, M. Engebretson, M. Lester, J. Watermann, and M. F. Marcucci

Subjects
Science, Physics, QC1-999, Geophysics. Cosmic physics, QC801-809
Abstract

During the interval between 8:00–9:30 on 14 January 2001, the four Cluster spacecraft were moving from the central magnetospheric lobe, through the dusk sector mantle, on their way towards intersecting the magnetopause near 15:00 MLT and 15:00 UT. Throughout this interval, the EISCAT Svalbard Radar (ESR) at Longyearbyen observed a series of poleward-moving transient events of enhanced F-region plasma concentration ("polar cap patches"), with a repetition period of the order of 10 min. Allowing for the estimated solar wind propagation delay of 75 ( ± 5) min, the interplanetary magnetic field (IMF) had a southward component during most of the interval. The magnetic footprint of the Cluster spacecraft, mapped to the ionosphere using the Tsyganenko T96 model (with input conditions prevailing during this event), was to the east of the ESR beams. Around 09:05 UT, the DMSP-F12 satellite flew over the ESR and showed a sawtooth cusp ion dispersion signature that also extended into the electrons on the equatorward edge of the cusp, revealing a pulsed magnetopause reconnection. The consequent enhanced ionospheric flow events were imaged by the SuperDARN HF backscatter radars. The average convection patterns (derived using the AMIE technique on data from the magnetometers, the EISCAT and SuperDARN radars, and the DMSP satellites) show that the associated poleward-moving events also convected over the predicted footprint of the Cluster spacecraft. Cluster observed enhancements in the fluxes of both electrons and ions. These events were found to be essentially identical at all four spacecraft, indicating that they had a much larger spatial scale than the satellite separation of the order of 600 km. Some of the events show a correspondence between the lowest energy magnetosheath electrons detected by the PEACE instrument on Cluster (10–20 eV) and the topside ionospheric enhancements seen by the ESR (at 400–700 km). We suggest that a potential barrier at the magnetopause, which prevents the lowest energy electrons from entering the magnetosphere, is reduced when and where the boundary-normal magnetic field is enhanced and that the observed polar cap patches are produced by the consequent enhanced precipitation of the lowest energy electrons, making them and the low energy electron precipitation fossil remnants of the magnetopause reconnection rate pulses.Key words. Magnetospheric physics (polar cap phenomena; solar wind – magnetosphere interactions; magnetosphere – ionosphere interactions)

Published
2001
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15. Observations of the cusp region under northward IMF

Author

F. Pitout, J.-M. Bosqued, D. Alcaydé, W. F. Denig, and H. Rème

Subjects
Science, Physics, QC1-999, Geophysics. Cosmic physics, QC801-809
Abstract

We present a comparative study of the cusp region using the EISCAT Svalbard Radars (ESR) and the Cluster spacecraft. We focus in this paper on 2 February 2001, over the time period from 07:30 UT to 12:00 UT when the oblique ESR antenna pointing northward at a low elevation recorded latitudinal motions of the cusp region in response to the IMF. Meanwhile, the Cluster satellites were flying over the EISCAT Svalbard Radar field-of-view around local magnetic noon. The spacecraft first flew near ESR, northeast of Svalbard and then passed over the field-of-view of the antenna at about 11:30 UT. From 08:00 UT to 09:00 UT, the IMF remains primarily southward yet several variations in the Z-component are seen to move the cusp. Around 09:00 UT, an abrupt northward turning of the IMF moves the cusp region to higher latitudes. As a result, the Cluster satellites ended up in the northernmost boundary of the high-altitude cusp region where the CIS instrument recorded highly structured plasma due to ion injections in the lobe of the magnetosphere. After 09:00 UT, the IMF remains northward for more than two hours. Over this period, the ESR records sunward plasma flow in the cusp region due to lobe reconnection, while Cluster spacecraft remain in the high-altitude cusp.Key words. Magnetospheric physics (magnetopause, cusp, and boundary layers; plasma convection) Ionosphere (polar ionosphere)

Published
2001
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16. Coordinated ground-based, low altitude satellite and Cluster observations on global and local scales during a transient post-noon sector excursion of the magnetospheric cusp

Author

H. J. Opgenoorth, M. Lockwood, D. Alcaydé, E. Donovan, M. J. Engebretson, A. P. van Eyken, K. Kauristie, M. Lester, J. Moen, J. Waterman, H. Alleyne, M. André, M. W. Dunlop, N. Cornilleau-Wehrlin, A. Masson, A. Fazerkerley, H. Rème, R. André, O. Amm, A. Balogh, R. Behlke, P. L. Blelly, H. Boholm, E. Borälv, J. M. Bosqued, S. Buchert, M. Candidi, J. C. Cerisier, C. Cully, W. F. Denig, P. Eglitis, R. A. Greenwald, B. Jackal, J. D. Kelly, I. Krauklis, G. Lu, I. R. Mann, M. F. Marcucci, I. W. McCrea, M. Maksimovic, S. Massetti, P. M. E. Décréau, D. K. Milling, S. Orsini, F. Pitout, G. Provan, J. M. Ruohoniemi, J. C. Samson, J. J. Schott, F. Sedgemore-Schulthess, R. Stamper, P. Stauning, A. Strømme, M. Taylor, A. Vaivads, J. P. Villain, I. Voronkov, J. A. Wild, and M. Wild

Subjects
Science, Physics, QC1-999, Geophysics. Cosmic physics, QC801-809
Abstract

On 14 January 2001, the four Cluster spacecraft passed through the northern magnetospheric mantle in close conjunction to the EISCAT Svalbard Radar (ESR) and approached the post-noon dayside magnetopause over Green-land between 13:00 and 14:00 UT. During that interval, a sudden reorganisation of the high-latitude dayside convection pattern occurred after 13:20 UT, most likely caused by a direction change of the Solar wind magnetic field. The result was an eastward and poleward directed flow-channel, as monitored by the SuperDARN radar network and also by arrays of ground-based magnetometers in Canada, Greenland and Scandinavia. After an initial eastward and later poleward expansion of the flow-channel between 13:20 and 13:40 UT, the four Cluster spacecraft, and the field line footprints covered by the eastward looking scan cycle of the Söndre Strömfjord incoherent scatter radar were engulfed by cusp-like precipitation with transient magnetic and electric field signatures. In addition, the EISCAT Svalbard Radar detected strong transient effects of the convection reorganisation, a poleward moving precipitation, and a fast ion flow-channel in association with the auroral structures that suddenly formed to the west and north of the radar. From a detailed analysis of the coordinated Cluster and ground-based data, it was found that this extraordinary transient convection pattern, indeed, had moved the cusp precipitation from its former pre-noon position into the late post-noon sector, allowing for the first and quite unexpected encounter of the cusp by the Cluster spacecraft. Our findings illustrate the large amplitude of cusp dynamics even in response to moderate solar wind forcing. The global ground-based data proves to be an invaluable tool to monitor the dynamics and width of the affected magnetospheric regions.Key words. Magnetospheric cusp, ionosphere, reconnection, convection flow-channel, Cluster, ground-based observations

Published
2001
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17. ESR and EISCAT observations of the response of the cusp and cleft to IMF orientation changes

Author

I. W. McCrea, M. Lockwood, J. Moen, F. Pitout, P. Eglitis, A. D. Aylward, J.-C. Cerisier, A. Thorolfssen, and S. E. Milan

Subjects
Science, Physics, QC1-999, Geophysics. Cosmic physics, QC801-809
Abstract

We report observations of the cusp/cleft ionosphere made on December 16th 1998 by the EISCAT (European incoherent scatter) VHF radar at Tromsø and the EISCAT Svalbard radar (ESR). We compare them with observations of the dayside auroral luminosity, as seen by meridian scanning photometers at Ny Ålesund and of HF radar backscatter, as observed by the CUTLASS radar. We study the response to an interval of about one hour when the interplanetary magnetic field (IMF), monitored by the WIND and ACE spacecraft, was southward. The cusp/cleft aurora is shown to correspond to a spatially extended region of elevated electron temperatures in the VHF radar data. Initial conditions were characterised by a northward-directed IMF and cusp/cleft aurora poleward of the ESR. A strong southward turning then occurred, causing an equatorward motion of the cusp/cleft aurora. Within the equatorward expanding, southward-IMF cusp/cleft, the ESR observed structured and elevated plasma densities and ion and electron temperatures. Cleft ion fountain upflows were seen in association with elevated ion temperatures and rapid eastward convection, consistent with the magnetic curvature force on newly opened field lines for the observed negative IMF By. Subsequently, the ESR beam remained immediately poleward of the main cusp/cleft and a sequence of poleward-moving auroral transients passed over it. After the last of these, the ESR was in the polar cap and the radar observations were characterised by extremely low ionospheric densities and downward field-aligned flows. The IMF then turned northward again and the auroral oval contracted such that the ESR moved back into the cusp/cleft region. For the poleward-retreating, northward-IMF cusp/cleft, the convection flows were slower, upflows were weaker and the electron density and temperature enhancements were less structured. Following the northward turning, the bands of high electron temperature and cusp/cleft aurora bifurcated, consistent with both subsolar and lobe reconnection taking place simultaneously. The present paper describes the large-scale behaviour of the ionosphere during this interval, as observed by a powerful combination of instruments. Two companion papers, by Lockwood et al. (2000) and Thorolfsson et al. (2000), both in this issue, describe the detailed behaviour of the poleward-moving transients observed during the interval of southward Bz, and explain their morphology in the context of previous theoretical work.Key words: Ionosphere (ionosphere - magnetosphere interactions; auroral ionosphere; plasma temperature and density)

Published
2000
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20. Interhemispheric Asymmetry of the Equatorial Ionization Anomaly (EIA) on the African Sector Over 3 Years (2014-2016): Effects of Thermospheric Meridional Winds

Author

A. Loutfi, F. Pitout, A. Bounhir, Z. Benkhaldoun, J. J. Makela, S. Abamni, K. Zyane, A. Elfakhiri, Institut de recherche en astrophysique et planétologie (IRAP), 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
EIA, Geophysics, FPI, thermospheric neutral winds, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Swarm, ionosphere, electron density
Abstract

International audience; Observations made by the Langmuir probes on board the Swarm satellites and the Fabry-Perot interferometer installed at the Oukaimeden Observatory in Morocco have been systematically analyzed to study the effect of geomagnetic activity on the thermosphere-ionosphere system over 3 years. The annual variation of the electron density (Ne) shows that during the day, the ionospheric density starts to increase at midlatitudes, with a single crest between 8 LT and 12 LT. It is also noticeable that the double crest structure is present between 12 LT and 00 LT: symmetric from 12 LT to 20 LT and asymmetric from 20 LT to 24 LT. Observations show strong seasonal variations, with Ne being lower around the June solstice. We have noticed the semiannual anomaly: Ne is higher around equinox than around solstice. For solstice seasons, the asymmetries in Ne are stronger at the December solstice than at the June solstice. For equinox seasons, we can notice equinoctial symmetry in all local time sectors, meaning that the same trend is observed for both equinoxes with or without symmetrical crests. The effect of meridional neutral winds on equatorial ionization anomaly (EIA) crests have been classified during both quiet and disturbed conditions. Over the studied region, the southward meridional winds have the tendency to enhance the northern crest of the EIA during quiet time and in a more pronounced way during geomagnetically disturbed conditions. Finally, we have quantified the relations between the thermospheric neutral winds data and the EIA by introducing an asymmetrical index.

Published
2022
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21. The Polar Cusp Seen by Cluster

Author

Y. V. Bogdanova, F. Pitout, Institut de recherche en astrophysique et planétologie (IRAP), 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
Physics, Geophysics, polar cusp, [SDU]Sciences of the Universe [physics], Space and Planetary Science, dayside magnetosphere, Physics::Space Physics, Cluster (physics), Cluster mission, Polar, Cusp (anatomy), Astrophysics
Abstract

International audience; The investigation of the magnetospheric polar cusps was one of the main objectives of the Cluster mission. The four satellites have crossed those regions numerous times over the years and, with their suitable instrumentation, favorable orbits, and unique multipoint measurements, many aspects of the cusp have been unveiled. The first of those is its highly dynamic nature. With four satellites, whatever their altitude and thus their configuration, the spatial/temporal ambiguity has been lifted and a completely new insight into the motion of the cusp and evolution of the transient small-scale structures within it was given. Second, the high altitude or exterior cusp, its properties and dynamics, magnetic configuration, the energetic particles observed within, and its boundary with the magnetosheath were characterized in a number of case studies and on a statistical basis. Third, the Cluster cusp observations brought a fresh eye on the reconnection process at the magnetopause, including its location and spatio-temporal variability. Finally, the complete payload with particle, field and wave detectors have made it possible to treat cusp as a plasma physics laboratory to progress our understanding of wave-particle interaction and turbulence within the cusp. We have no choice but to note that Cluster has been extremely successful for all these matters.

Published
2021
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22. Ionosphere-thermosphere coupling during the 22–23 June 2015 geomagnetic storm: Swarm and FPI coordinated observations above the Oukaimeden observatory

Author

F. Pitout, Z. Benkhaldoun, Jonathan J. Makela, Stephan Buchert, A. Bounhir, and A. Loutfi

Subjects
Geomagnetic storm, Northern Hemisphere, Magnetic dip, Storm, Atmospheric sciences, Physics::Geophysics, Observatory, Physics::Space Physics, Astrophysics::Earth and Planetary Astrophysics, Thermosphere, Ionosphere, Southern Hemisphere, Physics::Atmospheric and Oceanic Physics, Geology
Abstract

We investigate the response of the ionosphere-thermosphere coupled system to the 22-23 June 2015 geomagnetic storm in the region above the Oukaimeden observatory in Morocco with a Fabry-Perot interferometer and the Swarm satellites. The measured thermospheric neutral winds are strong enough to have two direct consequences. First, they create a strong asymmetry in the equatorial ionisation crests on both sides of the magnetic equator (actually, they make the southern hemisphere crest disappear). This asymmetry is explained by the southerly thermospheric neutral wind that was blowing during the storm and is shown to be favoured by the season. Second, within the northern hemisphere ionisation crest, Swarm A and C detect km-size electron density structures. Those may be ascribed to gradient drift instability.

Published
2021
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23. Simultaneous Polar and Cluster Observations in the Northern and Southern Middle‐Altitude Polar Cusps Around Equinox

Author

Jean Berchem, K. J. Trattner, C. P. Escoubet, F. Pitout, Aurélie Marchaudon, H. E. Laakso, Institut de recherche en astrophysique et planétologie (IRAP), 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), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), and 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)

Subjects
Physics, 010504 meteorology & atmospheric sciences, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Equinox, Atmospheric sciences, 01 natural sciences, [PHYS.PHYS.PHYS-SPACE-PH]Physics [physics]/Physics [physics]/Space Physics [physics.space-ph], Geophysics, Altitude, Space and Planetary Science, Hemispheric asymmetry, 0103 physical sciences, Cluster (physics), Polar, 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences
Abstract

International audience

Published
2020
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24. Solar surveillance with CLIMSO: instrumentation, database and on-going developments

Author

Luc Dettwiller, Arturo López Ariste, F. Pitout, Jean-Michel Glorian, L. Koechlin, Institut de recherche en astrophysique et planétologie (IRAP), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-Météo France-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-Météo France-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-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)-Centre National de la Recherche Scientifique (CNRS), Télescope héliographique pour l'étude du magnétisme et des instabilites solaires (THEMIS), Centre National de la Recherche Scientifique (CNRS), SFO Enseignement, SFO, 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, observation, 010504 meteorology & atmospheric sciences, Computer science, lcsh:QC851-999, Space weather, computer.software_genre, 7. Clean energy, 01 natural sciences, Solar prominence, coronagraphs, Observatory, 0103 physical sciences, Data file, Instrumentation (computer programming), 010303 astronomy & astrophysics, database, 0105 earth and related environmental sciences, MIDI, Database, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Suite, Sun, telescopes, computer.file_format, 13. Climate action, Space and Planetary Science, lcsh:Meteorology. Climatology, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], computer, Space environment
Abstract

International audience; CLIMSO is a suite of solar telescopes installed at Pic du Midi observatory in the southwest of France. It consists of two refractors that image the full solar disk in Hα and CaII K, and two coronagraphs that capture the prominences and ejections of chromospheric matter in Hα and HeI. Synoptic observations are carried out since 2007 and they follow those of previous instruments. CLIMSO, together with its predecessors, offer a temporal coverage of several solar cycles. With a direct access to its images, CLIMSO contributes to real time monitoring of the Sun. For that matter, the national research council for astrophysics (CNRS/INSU) has labelled CLIMSO as a national observation service for “surveillance of the Sun and the terrestrial space environment”. Products, under the form of images, movies or data files, are available via the CLIMSO DataBase. In this paper, we present the current instrumental configuration; we detail the available products and show how to access them; we mention some possible applications for solar and space weather; and finally, we evoke developments underway, both numerical to valorise our data, and instrumental to offer more and better capabilities.

Published
2020
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25. Thermospheric Neutral Winds Above the Oukaimeden Observatory: Effects of Geomagnetic Activity

Author

Aziza Bounhir, F. Pitout, A. Loutfi, Zouhair Benkhaldoun, Jonathan J. Makela, Institut de recherche en astrophysique et planétologie (IRAP), 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
superposed, observation of the thermosphereic neutral winds, Atmospheric sciences, quiet days, Solar cycle, comparison of the FPI with the HWM model, Geophysics, Earth's magnetic field, effects of the geomagnetic storms, Space and Planetary Science, Observatory, [SDU]Sciences of the Universe [physics], solar cycle, Environmental science
Abstract

International audience; In the context of space weather, we investigate the effect of geomagnetic activity on Earth's thermosphere above the Oukaimeden Observatory in Morocco (geographic coordinates: 31.206°N, 7.866°W; magnetic latitude: 22.77°N) over 3 years from 2014 to 2016. The observatory is equipped with a Fabry-Perot interferometer (FPI) that provides measurements of thermospheric wind speed. In this study 41 disturbed nights (with SYM-H ≤ -50 nT, Kp ≥ 5) were identified and analyzed. We have characterized the meridional and zonal winds variability and dependence on the solar cycle, during both quiet and disturbed conditions. We have classified the storm time meridional neutral winds into three types of variation. The first type is characterized by traveling atmospheric disturbance (TAD)-induced circulation: the first TAD coming from the north and the second TAD being transequatorial, coming from the south. This type of storm with TAD-induced circulation accounts for 59% of the cases. The second type exhibits only slight discrepancies between the disturbed and quiet night flows. These cases account for 33% of the cases. The third type is characterized by the transequatorial wind in whole the night. This last type accounts for 8% of the cases. Finally, we apply a superposed epoch analysis method on the FPI data, and the effect of each phase of the geomagnetic storm on the wind flow and vertical total electron content VTEC has been quantified.

Published
2020
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26. Correction to: Statistical Analysis of Solar Events Associated with Storm Sudden Commencements over One Year of Solar Maximum During Cycle 23: Propagation from the Sun to the Earth and Effects

Author

Monique Pick, Stephane Regnier, Brigitte Schmieder, F. Pitout, D. Fontaine, Michel Menvielle, Aurélie Marchaudon, Nicole Cornilleau-Wehrlin, Benjamin Grison, I. Zouganelis, Aude Chambodut, Karine Bocchialini, Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institute of Atmospheric Physics [Prague] (IAP), Czech Academy of Sciences [Prague] (CAS), HELIOS - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Institut de physique du globe de Strasbourg (IPGS), Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), 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, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), 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)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-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)-Centre National de la Recherche Scientifique (CNRS), Department of Mathematics, Physics and Electrical Engineering [Newcastle], University of Northumbria at Newcastle [United Kingdom], European Space Astronomy Centre (ESAC), European Space Agency (ESA), Czech Academy of Sciences [Prague] (ASCR), Institut Pierre-Simon-Laplace (IPSL), École normale supérieure - Paris (ENS Paris)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National d'Études Spatiales [Toulouse] (CNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X), Université Paris-Sud - Paris 11 (UP11), 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), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), HEPPI - LATMOS, Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)

Subjects
Physics, 010504 meteorology & atmospheric sciences, Meteorology, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Astronomy and Astrophysics, Storm, Solar maximum, 01 natural sciences, [PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], 13. Climate action, Space and Planetary Science, 0103 physical sciences, Statistical analysis, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, 0105 earth and related environmental sciences
Abstract

International audience; Taking the 32 storm sudden commencements (SSCs) listed by the International Service of Geomagnetic Indices (ISGI) of the Observatory de l’Ebre during 2002 (solar activity maximum in Cycle 23) as a starting point, we performed a multi-criterion analysis based on observations (propagation time, velocity comparisons, sense of the magnetic field rotation, radio waves) to associate them with solar sources, identified their effects in the interplanetary medium, and looked at the response of the terrestrial ionized and neutral environment. We find that 28 SSCs can be related to 44 coronal mass ejections (CMEs), 15 with a unique CME and 13 with a series of multiple CMEs, among which 19 (68%) involved halo CMEs. Twelve of the 19 fastest CMEs with speeds greater than 1000 km s−1 are halo CMEs. For the 44 CMEs, including 21 halo CMEs, the corresponding X-ray flare classes are: 4 X-class, 19 M-class, and 21 C-class flares. The probability for an SSC to occur is 75% if the CME is a halo CME. Among the 500, or even more, front-side, non-halo CMEs recorded in 2002, only 23 could be the source of an SSC, i.e. 5%. The complex interactions between two (or more) CMEs and the modification of their trajectories have been examined using joint white-light and multiple-wavelength radio observations. The detection of long-lasting type IV bursts observed at metric–hectometric wavelengths is a very useful criterion for the CME–SSC association. The events associated with the most depressed Dst values are also associated with type IV radio bursts. The four SSCs associated with a single shock at L1 correspond to four radio events exhibiting characteristics different from type IV radio bursts. The solar-wind structures at L1 after the 32 SSCs are 12 magnetic clouds (MCs), 6 interplanetary coronal mass ejections (ICMEs) without an MC structure, 4 miscellaneous structures, which cannot unambiguously be classified as ICMEs, 5 corotating or stream interaction regions (CIRs/SIRs), one CIR caused two SSCs, and 4 shock events; notethat one CIR caused two SSCs. The 11 MCs listed in 3 or more MC catalogs covering the year 2002 are associated with SSCs. For the three most intense geomagnetic storms (based on Dst minima) related to MCs, we note two sudden increases of the Dst, at the arrival of the sheath and the arrival of the MC itself. In terms of geoeffectiveness, the relation between the CME speed and the magnetic-storm intensity, as characterized using the Dst magnetic index, is very complex, but generally CMEs with velocities at the Sun larger than 1000 km s−1 have larger probabilities to trigger moderate or intense storms. The most geoeffective events are MCs, since 92% of them trigger moderate or intense storms, followed by ICMEs (33%). At best, CIRs/SIRs only cause weak storms. We show that these geoeffective events (ICMEs or MCs) trigger an increased and combined auroral kilometric radiation (AKR) and non-thermal continuum (NTC) wave activity in the magnetosphere, an enhanced convection in the ionosphere, and a stronger response in the thermosphere. However, this trend does not appear clearly in the coupling functions, which exhibit relatively weak correlations between the solar-wind energy input and the amplitude of various geomagnetic indices, whereas the role of the southward component of the solar-wind magnetic field is confirmed. Some saturation appears for Dst values

Published
2019
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27. Ionospheric plasma density structures associated with magnetopause motion: a case study using the Cluster spacecraft and the EISCAT Svalbard Radar

Author

C. P. Escoubet, F. Pitout, E. A. Lucek, and EGU, Publication

Subjects
Convection, Atmospheric Science, Magnetosphere, law.invention, Physics::Geophysics, Magnetosheath, law, Electric field, Earth and Planetary Sciences (miscellaneous), Radar, lcsh:Science, [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, Space and Planetary Science, Physics::Space Physics, [SDU.STU] Sciences of the Universe [physics]/Earth Sciences, Magnetopause, lcsh:Q, Ionosphere, lcsh:Physics
Abstract

On 5 January 2003, the footprint of the Cluster spacecraft, then orbiting in the dayside magnetosphere near the magnetopause, was in the close vicinity of the EISCAT Svalbard Radar (ESR) in the dayside afternoon sector. This configuration made possible the study of the magnetopause motion and its direct consequences on the ionospheric plasma at high latitude. Cluster observed multiple magnetopause crossings despite its high latitude, while on the ground the magnetic activity was very low, whereas the ionospheric plasma sounded by the ESR exhibited poleward moving plasma density structures. In this paper, we compare the satellite and radar data, in order to show that the plasma density structures are directly related to the magnetopause motion and its associated pulsed ionospheric flow. We propose that the variations in electric field make the convection velocity vary enough to alter the electron population by accelerating the chemistry in the F-region and act as a source of electron depletion. The magnetopause motion is in this case, a source of plasma density structures in the polar dayside ionosphere.

Published
2018

28. Statistical Analysis of Solar Events Associated with Storm Sudden Commencements over One Year of Solar Maximum During Cycle 23: Propagation from the Sun to the Earth and Effects

Author

F. Pitout, Stephane Regnier, Benjamin Grison, Brigitte Schmieder, Dominique Fontaine, Aurélie Marchaudon, Aude Chambodut, Karine Bocchialini, I. Zouganelis, Michel Menvielle, N. Cornilleau-Wehrlin, Monique Pick, Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institute of Atmospheric Physics [Prague] (IAP), Czech Academy of Sciences [Prague] (ASCR), HEPPI - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Département des sciences de la Terre, Université Paris-Sud - Paris 11 (UP11), Institut de physique du globe de Strasbourg (IPGS), Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), 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)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique des Plasmas (LPP), 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), 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), Department of Mathematics, Physics and Electrical Engineering [Newcastle], University of Northumbria at Newcastle [United Kingdom], European Space Astronomy Centre (ESAC), European Space Agency (ESA), Czech Academy of Sciences [Prague] (CAS), HELIOS - LATMOS, Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), 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, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), 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), Institut d'astrophysique spatiale ( IAS ), Université Paris-Sud - Paris 11 ( UP11 ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ), Institute of Atmospheric Physics [Prague] ( IAP ), Czech Academy of Sciences [Prague] ( ASCR ), 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 ), Université Paris-Sud - Paris 11 ( UP11 ), Institut de physique du globe de Strasbourg ( IPGS ), Université de Strasbourg ( UNISTRA ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ), 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 Diderot - Paris 7 ( UPD7 ) -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-École polytechnique ( X ) -Sorbonne Universités-PSL Research University ( PSL ) -Université Paris-Saclay-Centre National de la Recherche Scientifique ( CNRS ), Institut de recherche en astrophysique et planétologie ( IRAP ), Université Paul Sabatier - Toulouse 3 ( UPS ) -Observatoire Midi-Pyrénées ( OMP ) -Centre National de la Recherche Scientifique ( CNRS ), European Space Astronomy Center ( ESAC ), and European Space Agency ( ESA )

Subjects
010504 meteorology & atmospheric sciences, Interplanetary medium, FOS: Physical sciences, Auroral kilometric radiation, F500, Astrophysics, 01 natural sciences, Physics - Space Physics, 0103 physical sciences, Coronal mass ejection, Earth: SSC, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), 0105 earth and related environmental sciences, Geomagnetic storm, Physics, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Astronomy and Astrophysics, Solar maximum, Space Physics (physics.space-ph), Earth's magnetic field, Astrophysics - Solar and Stellar Astrophysics, Sun: CME, 13. Climate action, Space and Planetary Science, geoeffectiveness, Solar wind: ICME, Ionosphere, Thermosphere, [ SDU.ASTR.SR ] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR]
Abstract

Taking the 32 storm sudden commencements (SSCs) listed by ISGI during 2002 as a starting point, we performed a multi-criterion analysis based on observations (propagation time, velocity comparisons, sense of the magnetic field rotation, radio waves) to associate them with solar sources. We identified their effects in the interplanetary medium, and looked at the response of the terrestrial ionized and neutral environment. We find that 28 SSCs can be related to 44 coronal mass ejections (CMEs), 15 with a unique CME and 13 with a series of multiple CMEs, among which 19 involved halo CMEs; 12 of the 19 fastest CMEs with speeds greater than 1000 km/s are halo CMEs. The probability for an SSC to occur is 75% if the CME is a halo CME. The complex interactions between two CMEs and the modification of their trajectories have been examined using joint white-light and multiple-wavelength radio observations. The solar-wind structures at L1 after the shocks leading the 32 SSCs are 12 magnetic clouds (MCs), 6 interplanetary CMEs (ICMEs) without an MC structure, 4 miscellaneous structures, which cannot unambiguously be classified as ICMEs, 5 corotating or stream interaction regions (CIRs/SIRs), and 4 isolated shock events; note than one CIR caused two SSCs. The 11 MCs listed in 3 or more MC catalogs covering the year 2002 are associated with SSCs. For the 3 most intense geomagnetic storms related to MCs, we note 2 sudden increases of the Dst, at the arrival of the sheath and the arrival of the MC itself. The most geoeffective events are MCs, since 92% of them trigger moderate or intense storms, followed by ICMEs (33%). At best, CIRs/SIRs only cause weak storms. We show that these geoeffective events (ICMEs or MCs) trigger or reinforce terrestrial radiowave activity in the magnetosphere, an enhanced convection in the ionosphere, and a stronger response in the thermosphere., Comment: Solar Physics, in press

Published
2018
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29. Statistical Analysis of Solar Events Associated with Storm Sudden Commencements over One Year of Solar Maximum During Cycle 23: Propagation from the Sun to the Earth and Effects

Author

K. Bocchialini, B. Grison, M. Menvielle, A. Chambodut, N. Cornilleau-Wehrlin, D. Fontaine, A. Marchaudon, M. Pick, F. Pitout, B. Schmieder, S. Régnier, and I. Zouganelis

Subjects
010504 meteorology & atmospheric sciences, 0103 physical sciences, 010303 astronomy & astrophysics, 01 natural sciences, 0105 earth and related environmental sciences
Published
2018
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31. High-latitude ionospheric response to the solar eclipse of 1 August 2008: EISCAT observations and TRANSCAR simulation

Author

Pierre-Louis Blelly, D. Alcaydé, and F. Pitout

Subjects
Atmospheric Science, Electron density, Solar eclipse, Incoherent scatter, Astronomy, Geophysics, Physics::Geophysics, Latitude, Space and Planetary Science, Physics::Space Physics, Astrophysics::Solar and Stellar Astrophysics, Electron temperature, Astrophysics::Earth and Planetary Astrophysics, Ionosphere, Physics::Atmospheric and Oceanic Physics, Geology, Zenith, Eclipse
Abstract

On 1 August 2008, a total solar eclipse occurred and the footprint of its umbra passed North–East of the Svalbard archipelago, where the EISCAT Svalbard Radars (ESR) are installed. This eclipse is peculiar because it was seen at high-latitude, thus with large solar zenith angles and it was the first time that incoherent scatter radars were able to sound the ionospheric response at such a high latitude. The ESR data, after correction, show the typical signatures of a solar eclipse: depletion in electron density in the E- and F-regions, a decrease in electron temperature in the F-region, and a downflow of ions. Also, the UHF dish of the mainland EISCAT system measured a decrease in the same parameters, showing the influence of the penumbra (partial eclipse) on the ionosphere. We have modelled the response of the high-latitude ionosphere to this solar eclipse with the TRANSCAR code. Our simulations reproduce rather well the observations above the UHF radar in Tromso and the ESR on Svalbard. In particular, we show the influence of particle precipitation above the ESR and we suspect an effect above Tromso of the photoelectrons coming from the opposite hemisphere. Another interesting and quite unusual feature is the observation of the summer ionospheric cusp undergoing the eclipse. Radar data show structures of enhanced electron temperature, due to soft particle precipitation through the polar cusp.

Published
2013
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32. Cusp observations during a sequence of fast IMF BZ reversals

Author

S. E. Milan, M. Lockwood, F. Pitout, Y. V. Bogdanova, J. A. Davies, M. W. Dunlop, I. W. McCrea, H. T. Cai, and S. Y. Ma

Subjects
lcsh:Geophysics. Cosmic physics, Physics::Space Physics, lcsh:QC801-809, lcsh:Q, lcsh:Science, lcsh:Physics, lcsh:QC1-999
Abstract

In recent years, a large number of papers have reported the response of the cusp to solar wind variations under conditions of northward or southward Interplanetary Magnetic Field (IMF) Z-component (BZ). These studies have shown the importance of both temporal and spatial factors in determining the extent and morphology of the cusp and the changes in its location, connected to variations in the reconnection geometry. Here we present a comparative study of the cusp, focusing on an interval characterised by a series of rapid reversals in the BZ-dominated IMF, based on observations from space-borne and ground-based instrumentation. During this interval, from 08:00 to 12:00 UT on 12 February 2003, the IMF BZ component underwent four reversals, remaining for around 30 min in each orientation. The Cluster spacecraft were, at the time, on an outbound trajectory through the Northern Hemisphere magnetosphere, whilst the mainland VHF and Svalbard (ESR) radars of the EISCAT facility were operating in support of the Cluster mission. Both Cluster and the EISCAT were, on occasion during the interval, observing the cusp region. The series of IMF reversals resulted in a sequence of poleward and equatorward motions of the cusp; consequently Cluster crossed the high-altitude cusp twice before finally exiting the dayside magnetopause, both times under conditions of northward IMF BZ. The first magnetospheric cusp encounter, by all four Cluster spacecraft, showed reverse ion dispersion typical of lobe reconnection; subsequently, Cluster spacecraft 1 and 3 (only) crossed the cusp for a second time. We suggest that, during this second cusp crossing, these two spacecraft were likely to have been on newly closed field lines, which were first reconnected (opened) at low latitudes and later reconnected again (re-closed) poleward of the northern cusp. At ionospheric altitudes, the latitudinal excursions of the cusp/cleft region in response to the series of the IMF polarity changes were clearly captured by both the ESR and the Pykkvibaer radar of the SuperDARN HF network. The Open-Closed field-line Boundary (OCB) inferred from the HF radar observations underwent latitudinal variations in response to the IMF polarity changes that are in accordance with those predicted by Newell et al. (1989). Furthermore, variations in the ionospheric parameters yielded by the EISCAT VHF and ESR radars are basically consistent with inferences drawn from the HF radar observations. We conclude that Cluster spacecraft 1 and 3 crossed the cusp for a second time as a result of the latitudinal migration of the cusp in response to the IMF polarity reversals; at that time, however, the cusp lay poleward of spacecraft 4. Snapshots of the cusp from two DMSP satellite passes provide further support for this interpretation.

Published
2009

33. Cluster survey of the mid-altitude cusp – Part 2: Large-scale morphology

Author

Iannis Dandouras, Berndt Klecker, F. Pitout, C. P. Escoubet, Laboratoire de Planétologie de Grenoble (LPG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), European Space Research and Technology Centre (ESTEC), European Space Agency (ESA), Max-Planck-Institut für Extraterrestrische Physik (MPE), 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, MPE in Garching, Centre National d'Etudes Spatiales (CNES), Agence Spatiale Européenne = European Space Agency (ESA), 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, Scale (descriptive set theory), Astrophysics, cusp and boundary layers, 01 natural sciences, and boundary layers, 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), Cluster (physics), cusp, Proper time, Solar wind-magnetosphere interactions), Interplanetary magnetic field, lcsh:Science, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Physics, Cusp (singularity), lcsh:QC801-809, Geology, Astronomy and Astrophysics, Magnetospheric configuration and dy- namics, Geophysics, lcsh:QC1-999, Solar wind, lcsh:Geophysics. Cosmic physics, Magnetopause, Magnetospheric physics (Magnetopause, [SDU]Sciences of the Universe [physics], Space and Planetary Science, Magnetospheric configuration and dynamics, Magnetospheric physics, Physics::Space Physics, lcsh:Q, Solar wind-magnetosphere interactions, lcsh:Physics
Abstract

In this second part of our statistical study of the mid-altitude cusp, we compare the cusp morphology, as seen in the Cluster ion spectrometer (CIS), to the interplanetary magnetic field (IMF) orientation. We first recall the method we have used a) to define the cusp properties, b) to sort IMF conditions or behaviour in classes, c) to determine the proper time delay between the solar wind monitors and Cluster. Then, we define a few morphological features of the cusp and we relate these to the prevailing IMF. Our results reveal, among other things, that the occurrence of clearly dispersed ion structures in the cusp is 48%. From these dispersions, we infer the distance to reconnection site, which we relate to external conditions. In all other cases, the cusp exhibits a more disturbed behaviour in terms of ion structures and fall in our "discontinuous" or "irregular" categories. Among these, a few interesting cases of discontinuous cusps occurring under stable IMF conditions have been identified. They all occur when the IMF is dominated by its Y-component, which plays in principle in favour of anti-parallel reconnection but their wide MLT and latitudinal distributions is a priori incompatible with the anti-parallel reconnection hypothesis solely.

Published
2009
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34. Shape, size, velocity and field-aligned currents of dayside plasma injections: a multi-altitude study

Author

Andrew Fazakerley, Jean-Claude Cerisier, Malcolm Dunlop, F. Pitout, Aurélie Marchaudon, Jean-Michel Bosqued, 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), 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), Laboratoire de Planétologie de Grenoble (LPG), Université Joseph Fourier - Grenoble 1 (UJF)-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), 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)-Université Paris-Saclay-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 line, Magnetosphere, cusp and boundary layers, 01 natural sciences, Current sheet, Magnetosheath, 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), lcsh:Science, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Physics, Flux tube, Current systems, lcsh:QC801-809, Geology, Astronomy and Astrophysics, Geophysics, Magnetic flux, lcsh:QC1-999, Computational physics, Magnetic field, lcsh:Geophysics. Cosmic physics, Magnetopause, Plasma convec- tion, [SDU]Sciences of the Universe [physics], Space and Planetary Science, Magnetospheric physics, Physics::Space Physics, lcsh:Q, lcsh:Physics
Abstract

On 20 February 2005, Cluster in the outer magnetosphere and Double Star-2 (TC-2) at mid-altitude are situated in the vicinity of the northern cusp/mantle, with Cluster moving sunward and TC-2 anti-sunward. Their magnetic footprints come very close together at about 15:28 UT, over the common field-of-view of SuperDARN radars. Thanks to this conjunction, we determine the velocity, the transverse sizes, perpendicular and parallel to this velocity, and the shape of three magnetic flux tubes of magnetosheath plasma injection. The velocity of the structures determined from the Cluster four-spacecraft timing analysis is almost purely antisunward, in contrast with the antisunward and duskward convection velocity inside the flux tubes. The transverse sizes are defined from the Cluster-TC-2 separation perpendicular to the magnetic field, and from the time spent by a Cluster spacecraft in one structure; they are comprised between 0.6 and 2 RE in agreement with previous studies. Finally, using a comparison between the eigenvectors deduced from a variance analysis of the magnetic perturbation at the four Cluster and at TC-2, we show that the upstream side of the injection flux tubes is magnetically well defined, with even a concave front for the third one giving a bean-like shape, whereas the downstream side is far more turbulent. We also realise the first quantitative comparison between field-aligned currents at Cluster calculated with the curlometer technique and with the single-spacecraft method, assuming infinite parallel current sheets and taking into account the velocity of the injection flux tubes. The results agree nicely, confirming the validity of both methods. Finally, we compare the field-aligned current distribution of the three injection flux tubes at the altitudes of Cluster and TC-2. Both profiles are fairly similar, with mainly a pair of opposite field-aligned currents, upward at low-latitude and downward at high-latitude. In terms of intensity, the field-aligned currents at Cluster are two to three times less intense than at TC-2 for the first two flux tubes, in agreement with magnetic field line convergence. For the third flux tube, the intensity is equal, which is explained by the fact that TC-2 crosses the tube on its edge. Finally, the analysis of the ion and electron moments at Cluster shows that the field-aligned currents result from a small difference between upward ion and electron fluxes.

Published
2009
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35. Swarm and ESR observations of the ionospheric response to a field‐aligned current system in the high‐latitude midnight sector

Author

Aurélie Marchaudon, F. Pitout, Pierre-Louis Blelly, F. Forme, Stephan Buchert, X. Bai, Dag Arne Lorentzen, Institut de recherche en astrophysique et planétologie (IRAP), 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), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), and 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)

Subjects
010504 meteorology & atmospheric sciences, Incoherent scatter, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], 01 natural sciences, law.invention, Physics::Geophysics, symbols.namesake, law, Midnight, 0103 physical sciences, Langmuir probe, Radar, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Physics, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Conjunction (astronomy), Swarm behaviour, Geophysics, [PHYS.PHYS.PHYS-SPACE-PH]Physics [physics]/Physics [physics]/Space Physics [physics.space-ph], Physics::Space Physics, symbols, Orbit (dynamics), General Earth and Planetary Sciences, Ionosphere
Abstract

International audience; We present a conjunction between the Swarm fleet and the European Incoherent Scatter Svalbard Radar (ESR) on 9 January 2014. The Swarm orbit in the early phase of the mission gives us the unique opportunity of sequencing the temporal evolution of the observed field-aligned current system in the nightside, near magnetic local midnight. These field-aligned currents are seen to move poleward through the radar field of view and to affect the observed ionosphere. The upward field-aligned current (FAC) is responsible, at least in part, for the heating of the ionospheric electrons. It is less clear whether the downward FAC cools the ionosphere. We use the TRANSCAR model of the ionosphere to quantify the thermoelectric effect that comes into play. Finally, we compare the plasma parameters measured by the Langmuir probe on board Swarm and the ESR and conclude on an agreement within the errors.

Published
2015
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36. The science case for the EISCAT_3D radar

Author

Anita Aikio, Iwona Stanislawska, N. Engler, Stephan Buchert, C. J. Heinselman, Johan Kero, Hervé Lamy, Mark A. Clilverd, Yasunobu Ogawa, Lucilla Alfonsi, Kjellmar Oksavik, Michael Kosch, F. Pitout, Markus Rapp, Thomas Leyser, Ian McCrea, Asta Pellinen-Wannberg, Evgenia Belova, Björn Gustavsson, and Juha Vierinen

Subjects
Meteorology, Space weather, Computer science, Incoherent scatter, law.invention, Plasma physics, Solar system research, Fusion, plasma och rymdfysik, Space physics, Astronomi, astrofysik och kosmologi, law, Atmospheric science, Astronomy, Astrophysics and Cosmology, Radar, Remote sensing, Data processing, Radar techniques, VDP::Mathematics and natural science: 400::Physics: 430::Space and plasma physics: 437, Fusion, Plasma and Space Physics, EISCAT_3D, EISCAT, Pathfinder, Ultra high frequency, VDP::Matematikk og Naturvitenskap: 400::Fysikk: 430::Rom- og plasmafysikk: 437, General Earth and Planetary Sciences, Ionosphere
Abstract

The EISCAT (European Incoherent SCATer) Scientific Association has provided versatile incoherent scatter (IS) radar facilities on the mainland of northern Scandinavia (the EISCAT UHF and VHF radar systems) and on Svalbard (the electronically scanning radar ESR (EISCAT Svalbard Radar) for studies of the high-latitude ionised upper atmosphere (the ionosphere). The mainland radars were constructed about 30 years ago, based on technological solutions of that time. The science drivers of today, however, require a more flexible instrument, which allows measurements to be made from the troposphere to the topside ionosphere and gives the measured parameters in three dimensions, not just along a single radar beam. The possibility for continuous operation is also an essential feature. To facilitatefuture science work with a world-leading IS radar facility, planning of a new radar system started first with an EU-funded Design Study (2005–2009) and has continued with a follow-up EU FP7 EISCAT_3D Preparatory Phase project (2010–2014). The radar facility will be realised by using phased arrays, and a key aspect is the use of advanced software and data processing techniques. This type of software radar will act as a pathfinder for other facilities worldwide. The new radar facility will enable the EISCAT_3D science community to address new, significant science questions as well as to serve society, which is increasingly dependent on space-based technology and issues related to space weather. The location of the radar within the auroral oval and at the edge of the stratospheric polar vortex is also ideal for studies of the long-term variability in the atmosphere and global change. This paper is a summary of the EISCAT_3D science case, which was prepared as part of the EU-funded Preparatory Phase project for the new facility. Three science working groups, drawn from the EISCAT user community, participated in preparing this document. In addition to these working group members, who are listed as authors, thanks are due to many others in the EISCAT scientific community for useful contributions, discussions, and support. publishedVersion

Published
2015

37. Science opportunities from Cluster Swarm synergies

Author

O. Amm, H. Vanhamäki, K. Kauristie, N. Partamies, Claudia Stolle, F. Christiansen, S. C. Buchert, H. J. Opgenoorth, M. Dunlop, F. Pitout, P. Ritter, R. Haagmans, and M. G. G. T. Taylor

Published
2013

38. 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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39. Coordinated Cluster and Double Star observations of the dayside magnetosheath and magnetopause at different latitudes near noon

Author

Iannis Dandouras, F. Pitout, Chris Carr, Y. V. Bogdanova, A. Blagau, Andrew Fazakerley, C. P. Escoubet, and M. W. Dunlop

Subjects
Atmospheric Science, 010504 meteorology & atmospheric sciences, Equator, Soil Science, Magnetosphere, Astrophysics, Aquatic Science, Oceanography, 01 natural sciences, Magnetosheath, 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, Ecology, Paleontology, Forestry, Magnetic reconnection, Geophysics, Bow shocks in astrophysics, Earth's magnetic field, 13. Climate action, Space and Planetary Science, Physics::Space Physics, Magnetopause, Flux transfer event
Abstract

We present results of a favorable conjunction where the equatorial spacecraft (TC-1) of the Double Star mission exits the dayside magnetopause near the equator, while Cluster is inbound, near the southern cusp. This configuration makes it possible to compare observations of the magnetopause, around the same magnetic local time but at different latitudes. In this paper, we report on the general properties of the magnetosheath plasma at the two latitudes: unlike predictions from gasdynamic modeling, the density is found lower near the nose of the magnetopause than further downstream. Then, we present three interesting events. First, an FTE is observed at TC-1 and not at Cluster; we discuss the implications this has on the evolution of FTEs and on the size of the reconnection site. Then, a structure observed at both spacecraft is interpreted as a bulge progressing along the magnetopause. It is not clear whether this bulge is actually the remnant of an FTE or a running pulse that makes Cluster sense the reconnection layer. In any case, a rotational discontinuity is observed within it. At last, a northward turning of the magnetosheath magnetic field is observed at TC-1 and a reverse FTE is subsequently seen at Cluster, suggesting that magnetic reconnection is very fast to set up following a change in the IMF orientation.

Published
2008
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40. Effect of a northward turning of the interplanetary magnetic field on cusp precipitation as observed by Cluster

Author

M. W. Dunlop, Arnaud Masson, Andrew Fazakerley, H. E. Laakso, Matthew Taylor, Jean Berchem, H. Rème, P. W. Daly, Iannis Dandouras, C. P. Escoubet, F. Pitout, Karlheinz Trattner, and J. M. Bosqued

Subjects
Convection, Atmospheric Science, 010504 meteorology & atmospheric sciences, Soil Science, Magnetosphere, Aquatic Science, Oceanography, 01 natural sciences, Geochemistry and Petrology, 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), Interplanetary magnetic field, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, Physics, Ecology, Paleontology, Forestry, Geophysics, Geodesy, Magnetic field, 13. Climate action, Space and Planetary Science, Physics::Space Physics, Magnetopause, Cusp (anatomy), Polar, Magnetohydrodynamics
Abstract

The immediate effect of the rotation of the interplanetary magnetic field (IMF) from southward to northward on cusp precipitation has been rarely observed by a polar orbiting satellite in the past. The four Cluster spacecraft observed such an event on 23 September 2004 as they were crossing the polar cusp within 2–16 min from each other. Between the first three and the last spacecraft crossing the cusp, the IMF rotated from southward to northward with a dominant By (GSM) component. For the first time we can examine the changes in the particle precipitation immediately after such IMF change. The first two spacecraft observed typical IMF-southward ion dispersion, while the last one observed both an IMF-southward-like dispersion in the boundary layer and an IMF-northward dispersion in the cusp. After the IMF turning, the cusp is shown to have grown in size in both the poleward and equatorward directions. A three-dimensional magnetohydrodynamic simulation is used to determine the locations of the sources of the ions and the topology of the magnetic field during the event.

Published
2008
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41. Ionospheric Response to Flux Transfer Events at the Earth’s Magnetopause

Author

P. L. Blelly and F. Pitout

Subjects
Physics, Solar wind, Flux tube, Field line, Physics::Space Physics, Magnetopause, Magnetosphere, Magnetic reconnection, Geophysics, Ionosphere, Interplanetary magnetic field, Physics::Geophysics
Abstract

Flux transfer events (FTE) are thought to be the manifestation of the pulsed reconnection process by which interplanetary magnetic field lines and Earth’s magnetic field lines merge. They are observed at the magnetopause as bipolar signatures in the magnetic field component perpendicular to the magnetopause (normal component) as the distorted newly reconnected field lines get dragged by the magnetic tension and the solar wind. FTEs are also observed in the ionosphere by ground‐based instrumentations. Optical instruments commonly record poleward moving auroral forms in the red line (630nm) corresponding to low‐energy electron precipitation. SuperDARN radars observe the convection associated to FTEs as enhanced flow channels. The EISCAT radars on the Svalbard archipelago have revealed the transient and impulsive nature of the ionosphere under the polar cusp for southward IMF. We have performed a simulation of the ionospheric footprint of a FTE by including the Southwood model of FTE in the TRANSCAR model of ionosphere. We can trace the evolution of an open flux tube and the behaviour and dynamics of the surrounding ionospheric plasma. We particularly focus on the signature of the two areas of return flow on both side of the FTE footprint. Those return flow may actually be responsible of some of the structures observed by Incoherent Scatter radars such as the Eiscat Svalbard Radar (ESR). We then compare our simulations with observations and finally discuss the pros and cons of the Southwood model of FTE.

Published
2003
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42. Observations of the cusp region under northward IMF

Author

D. Alcaydé, William Denig, F. Pitout, Henri Rème, J. M. Bosqued, Swedish Institute of Space Physics [Kiruna] (IRF), 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, Air Force Research Laboratory (AFRL), United States Air Force (USAF), 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, Noon, 01 natural sciences, Latitude, Physics::Geophysics, Plasma flow, Ion injection, 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), lcsh:Science, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Computer Science::Information Theory, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, lcsh:QC801-809, Elevation, Geology, Astronomy and Astrophysics, Geophysics, Geodesy, lcsh:QC1-999, lcsh:Geophysics. Cosmic physics, Space and Planetary Science, Physics::Space Physics, Cusp (anatomy), lcsh:Q, lcsh:Physics
Abstract

We present a comparative study of the cusp region using the EISCAT Svalbard Radars (ESR) and the Cluster spacecraft. We focus in this paper on 2 February 2001, over the time period from 07:30 UT to 12:00 UT when the oblique ESR antenna pointing northward at a low elevation recorded latitudinal motions of the cusp region in response to the IMF. Meanwhile, the Cluster satellites were flying over the EISCAT Svalbard Radar field-of-view around local magnetic noon. The spacecraft first flew near ESR, northeast of Svalbard and then passed over the field-of-view of the antenna at about 11:30 UT. From 08:00 UT to 09:00 UT, the IMF remains primarily southward yet several variations in the Z-component are seen to move the cusp. Around 09:00 UT, an abrupt northward turning of the IMF moves the cusp region to higher latitudes. As a result, the Cluster satellites ended up in the northernmost boundary of the high-altitude cusp region where the CIS instrument recorded highly structured plasma due to ion injections in the lobe of the magnetosphere. After 09:00 UT, the IMF remains northward for more than two hours. Over this period, the ESR records sunward plasma flow in the cusp region due to lobe reconnection, while Cluster spacecraft remain in the high-altitude cusp.Key words. Magnetospheric physics (magnetopause, cusp, and boundary layers; plasma convection) Ionosphere (polar ionosphere)

Published
2001

43. High-latitude dayside ionosphere response to Pc5 field line resonance

Author

F. Pitout, P.-L. Blelly, P. Eglitis, European Space Agency, European Space Agency (ESA), Swedish Institute of Space Physics [Kiruna] (IRF), 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, Agence Spatiale Européenne = European Space Agency (ESA), 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, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, 01 natural sciences, Physics::Geophysics, Electric field, 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), lcsh:Science, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Physics, lcsh:QC801-809, Resonance, Geology, Astronomy and Astrophysics, Geophysics, lcsh:QC1-999, Magnetic field, lcsh:Geophysics. Cosmic physics, Earth's magnetic field, 13. Climate action, Space and Planetary Science, Physics::Space Physics, Electron temperature, Magnetopause, lcsh:Q, Ionosphere, lcsh:Physics
Abstract

We report observations of pulsations due to Field Line Resonance (FLR) in the morning sector of the high-latitude dayside ionosphere on 1 February 1998. The Geotail spacecraft, ideally skimming the dayside magnetopause, monitored the magnetopause motion, which is seen to induce a modulated response of the ionosphere by means of ULF waves. Pulsations in the Pc5 frequency range were observed in the ground magnetic field measured by the IMAGE array, as well as in the electron and ion temperatures measured by the EISCAT Svalbard Radar. The ion temperature oscillations are an indicator of a modulated convection electric field while field-aligned currents (FAC) associated with the FLR control the electron temperature. We have performed a simulation of the ionosphere experiencing sinusoidal FAC and electric field in order to confirm our hypothesis. In addition to the ionospheric response, the possible cause of the FLR and processes involved are also discussed.Key words. Magnetospheric physics (MHD waves and instabilities; magnetosphere-ionosphere interactions) – Ionosphere (polar ionosphere)

44. Coordinated ground-based, low altitude satellite and Cluster observations on global and local scales during a transient post-noon sector excursion of the magnetospheric cusp

Author

Peter Stauning, Olaf Amm, Pierrette Décréau, J. D. Kelly, Nicole Cornilleau-Wehrlin, G. Provan, P. Eglitis, Mark Lester, Ian R. Mann, Jim Wild, A. Masson, A. P. van Eyken, Mike Lockwood, W. F. Denig, Andris Vaivads, Matthew Taylor, F. Sedgemore-Schulthess, E. Borälv, Eric Donovan, J. J. Schott, D. Alcaydé, H. Alleyne, Stephan Buchert, I. C. Krauklis, Maurizio Candidi, R. Stamper, Joran Moen, J. P. Villain, Stefano Orsini, A. Strømme, A. Fazerkerley, A. Balogh, Milan Maksimovic, R. A. Greenwald, J. M. Ruohoniemi, Mark J. Engebretson, Jean-Claude Cerisier, D. K. Milling, Mats André, Malcolm Dunlop, H. Boholm, I. Voronkov, Jean-Michel Bosqued, M. N. Wild, Pierre-Louis Blelly, Gang Lu, Ian McCrea, John C. Samson, F. Pitout, H. J. Opgenoorth, Maria Federica Marcucci, J. Waterman, B. Jackal, Henri Rème, Kirsti Kauristie, R. André, Stefano Massetti, Christopher Cully, R. Behlke, Swedish Institute of Space Physics [Kiruna] (IRF), Finnish Meteorological Institute (FMI), STFC Rutherford Appleton Laboratory (RAL), Science and Technology Facilities Council (STFC), 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)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Department of Physics and Astronomy [Calgary], University of Calgary, Department of Physics [Minneapolis], Augsburg College, EISCAT Scientific Association [Norway], University of Leicester, University of Oslo (UiO), Danish Meteorological Institute (DMI), University of Sheffield [Sheffield], 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), European Space Research and Technology Centre (ESTEC), European Space Agency (ESA), Mullard Space Science Laboratory (MSSL), University College of London [London] (UCL), Istituto di Fisica dello Spazio Interplanetario (IFSI), Consiglio Nazionale delle Ricerche (CNR), Air Force Research Laboratory (AFRL), United States Air Force (USAF), Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), SRI International [Menlo Park] (SRI), National Center for Atmospheric Research [Boulder] (NCAR), University of York [York, UK], 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 Alberta, Ecole et Observatoire des sciences de la terre (EOST), Centre National de la Recherche Scientifique (CNRS)-Université Louis Pasteur - Strasbourg I-Institut national des sciences de l'Univers (INSU - CNRS), Danish Space Research Institute (DSRI), University of Tromsø (UiT), 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), Agence Spatiale Européenne = European Space Agency (ESA), National Research Council of Italy | Consiglio Nazionale delle Ricerche (CNR), Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Louis Pasteur - Strasbourg I-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), and Université Fédérale Toulouse Midi-Pyrénées

Subjects
Atmospheric Science, 010504 meteorology & atmospheric sciences, Field line, Incoherent scatter, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Noon, 01 natural sciences, 010305 fluids & plasmas, law.invention, Physics::Geophysics, law, 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), Radar, lcsh:Science, Physics::Atmospheric and Oceanic Physics, 0105 earth and related environmental sciences, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, lcsh:QC801-809, Geology, Astronomy and Astrophysics, Magnetic reconnection, Geophysics, lcsh:QC1-999, lcsh:Geophysics. Cosmic physics, Solar wind, 13. Climate action, Space and Planetary Science, Physics::Space Physics, Magnetopause, lcsh:Q, Ionosphere, lcsh:Physics
Abstract

On 14 January 2001, the four Cluster spacecraft passed through the northern magnetospheric mantle in close conjunction to the EISCAT Svalbard Radar (ESR) and approached the post-noon dayside magnetopause over Green-land between 13:00 and 14:00 UT. During that interval, a sudden reorganisation of the high-latitude dayside convection pattern occurred after 13:20 UT, most likely caused by a direction change of the Solar wind magnetic field. The result was an eastward and poleward directed flow-channel, as monitored by the SuperDARN radar network and also by arrays of ground-based magnetometers in Canada, Greenland and Scandinavia. After an initial eastward and later poleward expansion of the flow-channel between 13:20 and 13:40 UT, the four Cluster spacecraft, and the field line footprints covered by the eastward looking scan cycle of the Söndre Strömfjord incoherent scatter radar were engulfed by cusp-like precipitation with transient magnetic and electric field signatures. In addition, the EISCAT Svalbard Radar detected strong transient effects of the convection reorganisation, a poleward moving precipitation, and a fast ion flow-channel in association with the auroral structures that suddenly formed to the west and north of the radar. From a detailed analysis of the coordinated Cluster and ground-based data, it was found that this extraordinary transient convection pattern, indeed, had moved the cusp precipitation from its former pre-noon position into the late post-noon sector, allowing for the first and quite unexpected encounter of the cusp by the Cluster spacecraft. Our findings illustrate the large amplitude of cusp dynamics even in response to moderate solar wind forcing. The global ground-based data proves to be an invaluable tool to monitor the dynamics and width of the affected magnetospheric regions.Key words. Magnetospheric cusp, ionosphere, reconnection, convection flow-channel, Cluster, ground-based observations

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