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We present a statistical survey of large-amplitude, asymmetric plasma and magnetic field enhancements detected outside the diamagnetic cavity at comet 67P/Churyumov–Gerasimenko from December 2014 to June 2016. Based on the concurrent observations of plasma and magnetic field enhancements, we interpret them to be magnetosonic waves. The aim is to provide a general overview of these waves' properties over the mission duration. As the first mission of its kind, the ESA Rosetta mission was able to study the plasma properties of the inner coma for a prolonged time and during different stages of activity. This enables us to study the temporal evolution of these waves and their characteristics. In total, we identified ∼ 70 000 steepened waves in the magnetic field data by means of machine learning. We observe that the occurrence of these steepened waves is linked to the activity of the comet, where steepened waves are primarily observed at high outgassing rates. No clear indications of a relationship between the occurrence rate and solar wind conditions were found. The waves are found to propagate predominantly perpendicular to the background magnetic field, which indicates their compressional nature. Characteristics like amplitude, skewness, and width of the waves were extracted by fitting a skew normal distribution to the magnetic field magnitude of individual steepened waves. With increasing mass loading, the average amplitude of the waves decreases, while the skewness increases. Using a modified 1D magnetohydrodynamic (MHD) model, we investigated if the waves can be described by the combination of nonlinear and dissipative effects. By combining the model with observations of amplitude, width and skewness, we obtain an estimate of the effective plasma diffusivity in the comet–solar wind interaction region and compare it with suitable reference values as a consistency check. At 67P/Churyumov–Gerasimenko, these steepened waves are of particular importance as they dominate the innermost interaction region for intermediate to high activity.

Understanding physical processes that drive dynamics of the radiation belts - the high-energy charged particle population trapped by the geomagnetic field in the inner magnetosphere, is of great importance for science and society. In fact, this population dynamically interacts with the solar wind and geomagnetic field over various temporal and spatial scales, and can have significant impacts on its surrounding environment, including hazards to satellites and astronaut health. Understanding the relevant acceleration mechanisms of these particles can help not only to uncover the underlying physics, but also to improve our ability to predict and to protect. Despite numerous attempts over several decades, unfolding the dynamics of interactions in such systems is still one of the challenging research areas and has not yet been achieved, due to the complex and nonlinear underlying physics of the radiation belts. However, information theory is not constrained by such limitations and has proven itself to be a powerful non-parametric approach to discover the causal interactions among different nonlinear complex systems, and can be considered complementary to physics-based approaches. In this work, we apply entropy-based causality measures such as conditional mutual information to determine the information transfer between various variables including different solar wind parameters and geomagnetic activity indices obtained from NASA’s OmniWeb service and omnidirectional electron fluxes from the MagEIS units onboard Van Allen Probe B in the outer radiation belt, ranging in energy from a few keV to several MeV. We find significant information flow from low energy electrons into high energy ones as well as from some solar wind/geomagnetic field parameters into electron fluxes of various energies. We are confident that our results provide great prospects for future targeted research on the dynamical mechanisms underlying radiation belts dynamics.This work has benefitted from discussions within the International Space Science Institute (ISSI) Team # 455 “Complex Systems Perspectives Pertaining to the Research of the Near-Earth Electromagnetic Environment.” P.M. and M.P. are supported by the Czech Science Foundation, Project No. GA19-16066S and by the Czech Academy of Sciences, Praemium Academiae awarded to M. Paluš.

Owing to the ever-present solar wind, our vast solar system is full of plasmas. The turbulent solar wind, together with sporadic solar eruptions, introduces various space plasma processes and phenomena in the solar atmosphere all the way to the Earth's ionosphere and atmosphere and outward to interact with the interstellar media to form the heliopause and termination shock. Remarkable progress has been made in space plasma physics in the last 65 years, mainly due to sophisticated in-situ measurements of plasmas, plasma waves, neutral particles, energetic particles, and dust via space-borne satellite instrumentation. Additionally high technology ground-based instrumentation has led to new and greater knowledge of solar and auroral features. As a result, a new branch of space physics, i.e., space weather, has emerged since many of the space physics processes have a direct or indirect influence on humankind. After briefly reviewing the major space physics discoveries before rockets and satellites, we aim to review all our updated understanding on coronal holes, solar flares and coronal mass ejections, which are central to space weather events at Earth, solar wind, storms and substorms, magnetotail and substorms, emphasizing the role of the magnetotail in substorm dynamics, radiation belts/energetic magnetospheric particles, structures and space weather dynamics in the ionosphere, plasma waves, instabilities, and wave-particle interactions, long-period geomagnetic pulsations, auroras, geomagnetically induced currents (GICs), planetary magnetospheres and solar/stellar wind interactions with comets, moons and asteroids, interplanetary discontinuities, shocks and waves, interplanetary dust, space dusty plasmas and solar energetic particles and shocks, including the heliospheric termination shock. This paper is aimed to provide a panoramic view of space physics and space weather., Accepted for publication in IEEE Transactions on Plasma Science (2022)

The primary scientific goal of ICARUS (Investigation of Coronal AcceleRation and heating of solar wind Up to the Sun), a mother-daughter satellite mission, proposed in response to the ESA “Voyage 2050” Call, will be to determine how the magnetic field and plasma dynamics in the outer solar atmosphere give rise to the corona, the solar wind, and the entire heliosphere. Reaching this goal will be a Rosetta Stone step, with results that are broadly applicable within the fields of space plasma physics and astrophysics. Within ESA’s Cosmic Vision roadmap, these science goals address Theme 2: “How does the Solar System work?” by investigating basic processes occurring “From the Sun to the edge of the Solar System”. ICARUS will not only advance our understanding of the plasma environment around our Sun, but also of the numerous magnetically active stars with hot plasma coronae. ICARUS I will perform the first direct in situ measurements of electromagnetic fields, particle acceleration, wave activity, energy distribution, and flows directly in the regions in which the solar wind emerges from the coronal plasma. ICARUS I will have a perihelion altitude of 1 solar radius and will cross the region where the major energy deposition occurs. The polar orbit of ICARUS I will enable crossing the regions where both the fast and slow winds are generated. It will probe the local characteristics of the plasma and provide unique information about the physical processes involved in the creation of the solar wind. ICARUS II will observe this region using remote-sensing instruments, providing simultaneous, contextual information about regions crossed by ICARUS I and the solar atmosphere below as observed by solar telescopes. It will thus provide bridges for understanding the magnetic links between the heliosphere and the solar atmosphere. Such information is crucial to our understanding of the plasma physics and electrodynamics of the solar atmosphere. ICARUS II will also play a very important relay role, enabling the radio-link with ICARUS I. It will receive, collect, and store information transmitted from ICARUS I during its closest approach to the Sun. It will also perform preliminary data processing before transmitting it to Earth. Performing such unique in situ observations in the area where presumably hazardous solar energetic particles are energized, ICARUS will provide fundamental advances in our capabilities to monitor and forecast the space radiation environment. Therefore, the results from the ICARUS mission will be extremely crucial for future space explorations, especially for long-term crewed space missions.

International audience; Low Frequency (LF) ~22 Hz to 200 Hz plasmaspheric hiss was studied using a year of Polar plasma wave data occurring during solar cycle minimum. The waves are found to be most intense in the noon and early dusk sectors. When only the most intense LF (ILF) hiss were examined, they are found to be substorm dependent and most prominent in the noon sector. The noon sector ILF waves were also determined to be independent of solar wind ram pressure. The ILF hiss intensity are independent of magnetic latitude. ILF hiss is found to be highly coherent in nature. ILF hiss propagates at all angles relative to the ambient magnetic field. Circular, elliptical and linear/highly elliptically polarized hiss have been detected, with elliptical polarization the dominant characteristic. A case of linear polarized ILF hiss that occurred deep in the plasmasphere during geomagnetic quiet was noted. The waveforms and polarizations of ILF hiss are similar to those of intense high frequency (IHF) hiss.We propose the hypothesis that ~10‐100 keV substorm injected electrons gradient drift to dayside minimum B pockets close to the magnetopause to generate LF chorus. The closeness of this chorus to low altitude entry points into the plasmasphere will minimize wave damping and allow intense noon‐sector ILF hiss. The coherency of ILF hiss leads the authors to predict energetic electron precipitation into the midlatitude ionosphere and the electron slot formation during substorms. Several means of testing the above hypotheses are discussed.

A search for extremely slow (V sw < 300 km s−1) solar winds (ESSWs) at 1 au has been conducted using hourly average solar wind data from 1963 through 2021. 297 ESSW events were identified with an average duration of ∼2.0 ± 1.4 days. The lowest speed detected was 156 km s−1. Ten of the lowest-speed events were analyzed in detail. It was found that all 10 events were located at the ends of high-speed solar wind (HSSW) streams. The termination of the ESSWs was caused by high-density plasmas, either a corotating interaction region associated with the next HSSW stream or a heliospheric plasma sheet encounter. There was a greater occurrence of ESSW events in solar cycles 23 and 24 than in previous solar cycles. This phenomenon is associated with the much lower solar activity during these two cycles. The decrease in solar polar open magnetic fields was accompanied by an increase in low and midlatitude open magnetic fields. The ESSWs were accompanied by low interplanetary magnetic fields (4.4 ± 2.1 nT) and low negative interplanetary B z fields (−1.7 ± 1.5 nT), which led to extreme geomagnetic quiet: AE = 67 ± 78 nT and Dst = 2.2 ± 9.9 nT. We encourage magnetospheric researchers to use ESSW events to better understand the ground states of the magnetosphere and ionosphere.

In this erratum we rectify the parts of the paper that were not corrected before the publication of the paper. The conclusions of the paper are unchanged.

Collisionless plasma shocks (CPSs), forming when supersonic plasma streams encounter a magnetized obstacle, are invoked to explain the acceleration of ubiquitously energetic cosmic rays. It has long been theorized from magnetohydrodynamics, but not directly observed that the CPSs develop from the growth of small-amplitude, low-frequency plasma waves which excited by reflected ion beams from the obstacle. We present in situ observations of an entire formation sequence of the periodic plasma shocks by the MAVEN spacecraft’s magnetic field and particle instruments. The magnetometer first detected small-amplitude circularly polarized magnetosonic waves that further steepened and eventually evolved into periodic shocks. Moreover, differing from the traditional understanding, characterizations of the fast mode waves show that the free energy of the wave/shock generation is provided by newborn protons, and the increasing sunward proton fluxes provided persistent energy for wave steepening. The unusual evidence presents itself from the combination of two circumstances: radial-aligned (Sun-Mars) magnetic fields and Martian atmospheric atom (hydrogen) photoionization and solar wind pickup. These observations lead to the conclusion that newborn ions play a crucial role in the formation process of some CPSs in the astrophysical and space plasma.

Low frequency (LF) ~22 Hz to 200 Hz plasmaspheric hiss was studied using a year of Polarplasma wave data occurring during solar cycle minimum. The waves are found to be most intense in the noon and early dusk sectors. When only the most intense LF (ILF) hiss was examined, they are found to be substorm dependent and most prominent in the noon sector. The noon sector ILF waves were also determined to be independent of solar wind ram pressure. The ILF hiss intensity is independent of magnetic latitude. ILF hiss is found to be highly coherent in nature. ILF hiss propagates at all angles relative tothe ambient magnetic field. Circular, elliptical, and linear/highly elliptically polarized hiss have been detected, with elliptical polarization the dominant characteristic. A case of linear polarized ILF hiss that occurred deep in the plasmasphere during geomagnetic quiet was noted. The waveforms and polarizations of ILF hiss are similar to those of intense high frequency hiss. We propose the hypothesis that ~10–100 keV substorm injected electrons gradient drift to dayside minimum B pockets close to the magnetopause to generate LF chorus. The closeness of this chorus to low altitude entry points into the plasmasphere will minimize wave damping and allow intense noon‐sector ILF hiss. The coherency of ILF hiss leads the authors to predict energetic electron precipitation into the midlatitude ionosphere and the electron slot formation during substorms. Several means of testing the above hypotheses are discussed. References[1] Tsurutani, B.T., S.A. Park, B.J. Falkowski, J. Bortnik, G.S. Lakhina, A. Sen, J.S. Pickett, R. Hajra, M. Parrot, and P. Henri (2020), Low frequency (f < 200 Hz) Polar plasmasheric hiss: Coherent and intense, J. Geophys. Res. Spa. Phys., in press.

Learning from successful applications of methods originating in statistical mechanics or information theory in one scientific field (e.g. atmospheric physics or weather) can provide important insights or conceptual ideas for other areas (e.g. space sciences) or even stimulate new research questions and approaches. For instance, quantification and attribution of dynamical complexity in output time series of nonlinear dynamical systems is a key challenge across scientific disciplines. Especially in the field of space physics, an early and accurate detection of characteristic dissimilarity between normal and abnormal states (e.g. pre-storm activity vs. magnetic storms) has the potential to vastly improve space weather diagnosis and, consequently, the mitigation of space weather hazards. This presentation reports on the progress of a largely interdisciplinary International Team, combining expertise from both space physics and nonlinear physics communities, which was selected for funding by the International Space Science Institute (ISSI) in 2019. The Team attempts to combine advanced mathematical tools and identify key directions for future methodological progress relevant to space weather forecasting using Swarm, SuperMAG, and other space/ground datasets. By utilizing a variety of complementary modern complex systems based approaches, an entirely novel view on nonlinear magnetospheric variability is obtained. Taken together, the multiplicity of recently developed approaches in the field of nonlinear time series analysis offers great potential for uncovering relevant yet complex processes interlinking different geospace subsystems, variables and spatio-temporal scales. The Team provides a first-time systematic assessment of these techniques and their applicability in the context of geomagnetic variability.

Pioneer in space plasma research and AGU Fellow (1992)

International audience; It has been long theorized, but not directly observed, that low-frequency magnetosonic plasma waves can steepen and form shocks. We show an example of small-amplitude, sinusoidal magnetosonic waves at the proton gyrofrequency upstream of the Martian bow shock. We hypothesize that these waves are produced by an ion beam instability associated with the ionization of hydrogen atoms by charge exchange with solar wind protons, solar photoionization, and/or electron impact ionization. As the waves are convected toward the planet by solar wind flow, the wave amplitude grows due to additional free energy put into the system by further ion beam particles. Finally, the steepened waves form shocks. Because of their development, the shocks are periodic with the separation at the proton gyroperiod. These observations lead to the conclusion that newborn ions may play a crucial role in the formation process of some collisionless plasma shocks in astrophysical and space plasmas.

We study the evolution of a cometary ionosphere, using approximately two years of plasma measurements by the Mutual Impedance Probe on board the Rosetta spacecraft monitoring comet 67P/Churyumov-Gerasimenko (67P) during August 2014–September 2016. The in situ plasma density measurements are utilized to estimate the altitude-integrated electron number density or cometary ionospheric total electron content (TEC) of 67P based on the assumption of radially expanding plasma. The TEC is shown to increase with decreasing heliocentric distance (rh) of the comet, reaching a peak value of ~(133 ± 84) × 109cm−2averaged around perihelion (rh< 1.5 au). At large heliocentric distances (rh> 2.5 au), the TEC decreases by ~2 orders of magnitude. For the same heliocentric distance, TEC values are found to be significantly larger during the post-perihelion periods compared to the pre-perihelion TEC values. This “ionospheric hysteresis effect” is more prominent in the southern hemisphere of the comet and at large heliocentric distances. A significant hemispheric asymmetry is observed during perihelion with approximately two times larger TEC values in the northern hemisphere compared to the southern hemisphere. The asymmetry is reversed and stronger during post-perihelion (rh> 1.5 au) periods with approximately three times larger TEC values in the southern hemisphere compared to the northern hemisphere. Hemispheric asymmetry was less prominent during the pre-perihelion intervals. The correlation of the cometary TEC with the incident solar ionizing fluxes is maximum around and slightly after perihelion (1.5 au 2.5 au) where the photo-ionization contribution to the TEC variability decreases. The results are discussed based on cometary ionospheric production and loss processes.

The near-Earth solar wind is in general super-Alfvénic and supermagnetosonic. Using all available near-Earth solar wind measurements between 1973 and 2020, we identified 30 intervals with sub-Alfvénic solar winds. The majority (83%) of the events occurred within interplanetary coronal mass ejection magnetic clouds (MCs)/driver gases. These MC sub-Alfvénic events are characterized by exceptionally low plasma densities (N sw) of ∼0.04–1.20 cm−3, low temperatures (T sw) of ∼0.08 × 105 K to 12.46 × 105 K, enhanced magnetic field intensities (B 0) of ∼8.3–53.9 nT, and speeds (V sw) of ∼328–949 km s−1. The resultant high Alfvén wave speeds (V A) ranged from ∼410 to 1471 km s−1. This is consistent with a mechanism of the MC expansions as they propagate radially outward, causing small pockets of sub-Alfvénic wind regions within the MCs. The remainder of the sub-Alfvénic intervals (17%) occurred within the extreme trailing portions of solar wind high-speed streams (HSSs). These HSS sub-Alfvénic winds had low N sw of ∼0.04–0.97 cm−3, low T sw of ∼0.06 × 105 K to 0.46 × 105 K, B 0 of ∼6.3–18.2 nT, V sw of ∼234–388 km s−1, and a V A range of ∼364–626 km s−1. This is consistent with a mechanism of solar wind super-radial expansions in the trailing HSS regions. During sub-Alfvénic solar wind intervals, Earth's bow shock nose exhibited rapid evanescence, and the estimated geocentric magnetopause distance increased by ∼33%–86%. The inner magnetosphere was more or less unaffected by the sub-Alfvénic solar winds. No significant impact was observed in the outer radiation belt relativistic electrons, and no geomagnetic storms or substorms were triggered during the sub-Alfvénic solar wind events.

It is found that the coupling between the solar wind and polar geomagnetic activity cause the annual and semiannual variation of auroral electrojet. The wavelet spectrum of the SuperMAG index, SML and SMU shows that both of the semiannual and annual variations are permanent features, and spectral power of the annual period of SML and SMU are stronger than that of the semiannual period. Due to coupling of the annual variation and the semiannual variation of SML, the diurnal variation of SML in summer months is not well correlated with results anticipated from the previous principle hypotheses [McIntosh, 1959; Russell and McPherron, 1973; Svalgaard, 1977; Cliver et al., 2000; Newell et al., 2013]. The annual/semiannual variation of SML and SMU is typically coupled together and is dependent on the local time and latitudinal variations of ionospheric conductivity and the electric field. A new index, the annual-corrected SMO index (SMO*), was suggested to indicate the semiannual variation of the westward auroral electrojet (SML). The seasonal-UT distribution of SMO* has good correlation with that predicted by the equinoctial hypothesis [McIntosh, 1959; Svalgaard, 2011].

The occurrence of geomagnetically induced currents (GICs) poses serious threats to modern technological infrastructure. Large GICs result from sharp variations of the geomagnetic field (dB/dt) caused by changes of large-scale magnetospheric and ionospheric currents. Intense dB/dt perturbations are known to occur often in high-latitude regions as a result of storm time substorms. Magnetospheric compressions usually caused by interplanetary shocks increase the magnetopause current leading to dB/dt perturbations more evident in midlatitude to low-latitude regions, while they increase the equatorial electrojet current leading to dB/dt perturbations in dayside equatorial regions. We investigate the effects of shock impact angles and speeds on the subsequent dB/dt perturbations with a database of 547 shocks observed at the L1 point. By adopting the threshold of dB/dt = 100 nT/min, identified as a risk factor to power systems, we find that dB/dt generally surpasses this threshold when following impacts of high-speed and nearly frontal shocks in dayside high-latitude locations. The same trend occurs at lower latitudes and for all nightside events but with fewer high-risk events. Particularly, we found nine events in equatorial locations with dB/dt > 100 nT/min. All events were caused by high-speed and nearly frontal shock impacts and were observed by stations located around noon local time. These high-risk perturbations were caused by sudden strong and symmetric magnetospheric compressions, more effectively intensifying the equatorial electrojet current, leading to sharp dB/dt perturbations. We suggest that these results may provide insights for GIC forecasting aiming at preventing degradation of power systems due to GICs.

International audience; An alternative scenario to the Ngwira et al. (2014, https://doi-org.insu.bib.cnrs.fr/10.1002/2013JA019661) high sheath densities is proposed for modeling the Carrington magnetic storm. Typical slow solar wind densities (~5 cm−3) and lower interplanetary magnetic cloud magnetic field intensities (~90 nT) can be used to explain the observed initial and main phase storm features. A second point is that the fast storm recovery may be explained by ring current losses due to electromagnetic ion cyclotron wave scattering.

The purpose of this study is to present a wavelet interactive filtering and reconstruction technique and apply this to the solar wind magnetic field components detected at the L1 Lagrange point ∼ 0.01 AU upstream of the Earth. These filtered interplanetary magnetic field (IMF) data are fed into a model to calculate a time series which we call AE∗. This model was adjusted assuming that magnetic reconnection associated with southward-directed IMF Bz is the main mechanism transferring energy into the magnetosphere. The calculated AE∗ was compared to the observed AE (auroral electrojet) index using cross-correlation analysis. The results show correlations as high as 0.90. Empirical removal of the high-frequency, short-wavelength Alfvénic component in the IMF by wavelet decomposition is shown to dramatically improve the correlation between AE∗ and the observed AE index. It is envisioned that this AE∗ can be used as the main input for a model to forecast relativistic electrons in the Earth's outer radiation belts, which are delayed by ∼ 1 to 2 days from intense AE events.

During intense magnetic storms, prompt penetration electric fields (PPEFs) through E × B forces near the magnetic equator uplift the dayside ionosphere. This effect has been called the dayside super-fountain effect. Ion-neutral drag forces between the upward moving O+ (oxygen ions) and oxygen neutrals will elevate the oxygen atoms to higher altitudes. This paper gives a linear calculation indicating how serious the effect may be during an 1859-type (Carrington) superstorm. It is concluded that the oxygen neutral densities produced at low-Earth-orbiting (LEO) satellite altitudes may be sufficiently high to present severe satellite drag. It is estimated that with a prompt penetrating electric field of ∼ 20 mV m−1 turned on for 20 min, the O atoms and O+ ions are uplifted to 850 km where they produce about 40-times-greater satellite drag per unit mass than normal. Stronger electric fields will presumably lead to greater uplifted mass.

The impact of a high-speed solar wind stream (HSS) on the topside near-equatorial ionosphere (Arecibo: 28.17°N, L = 1.3) is investigated for the first time. Although the HSS did not lead to any significant geomagnetic storm activity, the ionosphere over Arecibo became hotter and expanded significantly in altitude as compared to a non-HSS interval. The O+/H+ transition height hT increased by ~200 km in the daytime and by ~100 km at night. At the hT, the peak ionospheric electron and ion temperatures increased by ~200-500 K during day and by ~50-70 K at night. While the O+ ion concentration exhibited an overall enhancement, deep penetration of the H+ ions below hT are observed during the day. The noontime peak electron density was ~4 times higher during the HSS event compared to the non-HSS interval. We present three possible mechanisms to explain this topside ionospheric heating.

Bursty Bulk Flows (BBFs) have been correlated with Pi2 pulsations and damping oscillations of plasma velocity in many investigations. But the oscillation time scales in BBFs is still an open question. The purpose of this study is to statistically study the oscillated frequency distribution of magnetic field and plasma parameters inside BBFs. The data are obtained by the Time History of Events and Macroscale Interactions during Substorms (THEMIS) probes during the period of 2008 to 2011. For 424 selected BBF events, we use the wavelet spectrum analysis to select the main, second and third period components of the magnetic field and plasma parameters according to their largest, second and third-largest values of the wavelet power spectral density, respectively. The power spectra show repeated information in the form of multiple peaks or oscillations. The quasi-Gaussian distribution is a good model for the occurrences of the main and secondary periods. The most probable main periods of the magnetic field and plasma parameters are between 143 s and 160 s, which located in the frequency band of Pi2 and Pi3 pulsations. The second and third period ranges from 63 s to 70 s and from 34 s to 37 s, respectively. Main periods of these parameters change little with the radial distance. We conclude that periods of these parameters are formed at the beginning of BBF history. Although the distribution model cannot give the dynamic processes, it identifies the intrinsic frequencies in oscillations of magnetic field and ion velocity inside of BBFs.

Coherency (C) and ellipticity (e) of electromagnetic ion cyclotron (EMIC) waves are studied using Cassini data in the Earth's dayside low-latitude magnetosphere from L = 7 to 10. The results are compared with linear kinetic theory, 1-D and 2-D simulations. The EMIC waves are observed to occur in packets with multiple wave cycles. The wave cycles within a wave packet are observed to have the same general propagation angle θkB0 and polarization. In observations and 2-D simulations, EMIC waves have a mixture of circular and elliptical polarization for θkB0 60°, the waves are nearly linearly polarized (|e|≤0.1). This general trend is in good agreement with linear kinetic theory and 1-D simulations. Observations indicate right-hand (RH) wave packets to be interspersed with the left-hand (LH) wave packets. We show for the first time from linear theory that ion temperature anisotropies can generate RH waves at large propagation angles and for plasma beta βi>0.05. The observed mixture of RH and LH waves in the magnetosphere could be due to this direct generation of RH waves. Observations and simulations show that EMIC waves are coherent with 0.5 < C < 1.0 for θkB0≤50°. Here C is measured as the maximum value of cross-correlation coefficient between the transverse magnetic field components of the wave.

A study of dayside plasmaspheric hiss at frequencies from ~22 Hz to ~1.0 kHz was carried out using one year of Polar data. It is shown that intense, dayside plasmaspheric hiss is correlated with solar wind pressure with P > 2.5 nPa. The dayside effect is most prominent in the ~300 to ~650 Hz range. Intense dayside waves are also present during SYM-H

Entidad financiadora : Indian National Science Academy, New Delhi, India under the INSA Honorary Scientist Scheme