pinecone/core-2020-05-10-deduplication huggingface dataset:
Fundamental properties of substorm time energetic electrons in the inner magnetosphere

We studied fundamental properties of spatial-temporal evolution of energetic electrons trapped in the inner magnetosphere (L ≤ 7.4) during an isolated substorm by using a four-dimensional drift kinetic simulation under the time-dependent electric and magnetic fields provided by a global magnetohydrodynamics (MHD) simulation. When the interplanetary magnetic field turns southward, both the potential and induction electric fields start to increase in the inner magnetosphere, resulting in a gradual injection of low-energy electrons (≤51.9 keV) and deceleration of high-energy electrons (≥114 keV). The deceleration of high-energy electrons results in a decrease in the phase space density of the high-energy electrons during the growth phase. After a while, an abrupt transition of phase state (a substorm onset) occurs in the magnetosphere, which triggers abrupt changes in the magnetosphere and ionosphere. The AL index decreases rapidly, and magnetic field lines become dipole-like. The dipolarization does not proceed smoothly in the inner magnetosphere because of significant force imbalance between the J × B force and the grad P force. As a consequence, the electric field oscillates with a period of 2–3 min, resulting in multiple injections of the low-energy electrons. The low- and high-energy electrons are accelerated under the strong influence of the drift betatron and gyro betatron, so that the acceleration process is essentially nonlinear. Our simulation results suggest that the force-induced processes play an essential role in the substorm-associated redistribution of energetic particles in the inner magnetosphere
Asymmetry of magnetosheath flows and magnetopause shape during low Alfven Mach number solar wind

Copyright © 2013 American Geophysical Union (AGU)Previous works have emphasized the significant influence of the solar wind Alfvén Mach number (MA) on magnetospheric dynamics. Here we report statistical, observational results that pertain to changes in the magnetosheath flow distribution and magnetopause shape as a function of solar wind MA and interplanetary magnetic field (IMF) clock angle orientation. We use all Cluster 1 data in the magnetosheath during the period 2001–2010, using an appropriate spatial superposition procedure, to produce magnetosheath flow distributions as a function of location in the magnetosheath relative to the IMF and other parameters. The results demonstrate that enhanced flows in the magnetosheath are expected at locations quasi-perpendicular to the IMF direction in the plane perpendicular to the Sun-Earth line; in other words, for the special case of a northward IMF, enhanced flows are observed on the dawn and dusk flanks of the magnetosphere, while much lower flows are observed above the poles. The largest flows are adjacent to the magnetopause. Using appropriate magnetopause crossing lists (for both high and low MA), we also investigate the changes in magnetopause shape as a function of solar wind MA and IMF orientation. Comparing observed magnetopause crossings with predicted positions from an axisymmetric semi-empirical model, we statistically show that the magnetopause is generally circular during high MA, while is it elongated (albeit with moderate statistical significance) along the direction of the IMF during low MA. These findings are consistent with enhanced magnetic forces that prevail in the magnetosheath during low MA. The component of the magnetic forces parallel to the magnetopause produces the enhanced flows along and adjacent to the magnetopause, while the component normal to the magnetopause exerts an asymmetric pressure on the magnetopause that deforms it into an elongated shape
Terrestrial myriametric radio burst observed by IMAGE and Geotail satellites

We report the simultaneous detection of a terrestrial myriametric radio burst (TMRB) by IMAGE and Geotail on 19 August 2001. The TMRB was confined in time (0830–1006 UT) and frequency (12–50 kHz). Comparisons with all known nonthermal myriametric radiation components reveal that the TMRB might be a distinct radiation with a source that is unrelated to the previously known radiation. Considerations of beaming from spin-modulation analysis and observing satellite and source locations suggest that the TMRB may have a fan beamlike radiation pattern emitted by a discrete, dayside source located along the poleward edge of magnetospheric cusp field lines. TMRB responsiveness to IMF Bz and By orientations suggests that a possible source of the TMRB could be due to dayside magnetic reconnection instigated by northward interplanetary field condition
Simulated Energetic Particle Transport in the Interplanetary Space: The
  Palmer Consensus Revisited

Reproducing measurements of the scattering mean free paths for energetic
particles propagating through the solar system has been a major problem in
space physics. The pioneering work of Bieber et al. [Astrophys. J. 420, 294
(1994)] provided a theoretical explanation of such observations, which,
however, was based on assumptions such as the questionable hypothesis that
quasi-linear theory is correct for parallel diffusion. By employing a hybrid
plasma-wave/magnetostatic turbulence model, a test-particle code is used to
investigate the scattering of energetic particles. The results show excellent
agreement with solar wind observations.Comment: 8 pages, 3 figures, accepted for publication in J. Geophys. Re
UVCS/SoHO Catalog of Coronal Mass Ejections from 1996 to 2005:
  Spectroscopic Proprieties

Ultraviolet spectra of the extended solar corona have been routinely obtained
by SoHO/UVCS since 1996. Sudden variations of spectral parameters are mainly
due to the detection of Coronal Mass Ejections (CMEs) crossing the instrumental
slit. We present a catalog of CME ultraviolet spectra based upon a systematic
search of events in the LASCO CME catalog, and we discuss their statistical
properties. Our catalog includes 1059 events through the end of 2005, covering
nearly a full solar cycle. It is online available at the URL
http://solarweb.oato.inaf.it/UVCS_CME and embedded in the online LASCO CME
catalog (http://cdaw.gsfc.nasa.gov/CME_list). The emission lines observed
provide diagnostics of CME plasma parameters, such as the light-of-sight
velocity, density and temperature and allow to link the CME onset data to the
extended corona white-light images. The catalog indicates whether there are
clear signatures of features such as shock waves, current sheets, O VI flares,
helical motions and which part of the CME structures (front, cavity or
prominence material) are detected. The most common detected structure is the
cool prominence material (in about 70% of the events). For each event, the
catalog also contains movie, images, plots and information relevant to address
detailed scientific investigations. The number of events detected in UV is
about 1/10 of the LASCO CMEs, and about 1/4 of the halo events. We find that
UVCS tends to detect faster, more massive and energetic CME than LASCO and for
about 40% of the events events it has been possible to determine the plasma
light-of-sight velocity.Comment: 19 pages, 16 figure, 3 tables, Accepted by JG
Production of small-scale Alfvén waves by ionospheric depletion, nonlinear magnetosphere-ionosphere coupling and phase mixing

The authors acknowledge the International Space Science Institute (Switzerland) for funding the program that inspired this work. AJBR is grateful to the Royal Commission for the Exhibition of 1851 for present support and acknowledges an STFC studentship that funded part of this work.Rockets and satellites have previously observed small-scale Alfven waves inside large-scale downward field-aligned currents, and numerical simulations have associated their formation with self-consistent magnetosphere-ionosphere coupling. The origin of these waves was previously attributed to ionospheric feedback instability; however, we show that they arise in numerical experiments in which the instability is excluded. A new interpretation is proposed in which strong ionospheric depletion and associated current broadening (a nonlinear steepening/wave-breaking process) form magnetosphereionosphere waves inside a downward current region and these oscillations drive upgoing inertial Alfven waves in the overlying plasma. The resulting waves are governed by characteristic periods, which are a good match to previously observed periods for reasonable assumed conditions. Meanwhile, wavelengths perpendicular to the magnetic field initially map to an ionospheric scale comparable to the electron inertial length for the low-altitude magnetosphere, but become shorter with time due to frequency-based phase mixing of boundary waves (a new manifestation of phase mixing). Under suitable conditions, these could act as seeds for the ionospheric feedback instability.Publisher PDFPeer reviewe
Thermospheric atomic oxygen density estimates using the EISCAT Svalbard Radar

Coupling between the ionized and neutral atmosphere through particle collisions allows an indirect study of the neutral atmosphere through measurements of ionospheric plasma parameters. We estimate the neutral density of the upper thermosphere above ~250 km with the European Incoherent Scatter Svalbard Radar (ESR) using the year-long operations of the International Polar Year from March 2007 to February 2008. The simplified momentum equation for atomic oxygen ions is used for field-aligned motion in the steady state, taking into account the opposing forces of plasma pressure gradients and gravity only. This restricts the technique to quiet geomagnetic periods, which applies to most of the International Polar Year during the recent very quiet solar minimum. The method works best in the height range ~300–400 km where our assumptions are satisfied. Differences between Mass Spectrometer and Incoherent Scatter and ESR estimates are found to vary with altitude, season, and magnetic disturbance, with the largest discrepancies during the winter months. A total of 9 out of 10 in situ passes by the CHAMP satellite above Svalbard at 350 km altitude agree with the ESR neutral density estimates to within the error bars of the measurements during quiet geomagnetic periods
Midlatitude propagation of VLF to MF waves through nighttime ionosphere above powerful VLF transmitters

International audience[1] Midlatitude nighttime observations made by the DEMETER satellite in the very low frequency (VLF) to medium frequency (MF) bands (3 kHz to 3 MHz) have demonstrated the propagation of radio waves from the bottom of ionosphere up to the satellite altitude (~700 km). Propagation characteristics derived from the magneto-ionic theory [Budden, 1985] are used to explain the absence of wave observations between ~1 and 2 MHz. Under hypotheses made for the Appleton and Hartree (or Appleton and Lassen) formula, studies of the vertical variations of the real and imaginary parts of the refractive index are performed to point out modifications in the propagation characteristics of the waves: (i) at the crossing of the plasma cutoffs regions, (ii) at the crossing of the ordinary and extraordinary mode resonance regions, and (iii) in the region where the product of the collision frequency (n) and the electronic density (Ne) is maximum. It is shown that enhancements in the collision frequencies, produced by powerful VLF transmitters in the region where the product of n and Ne is maximum, open the half angle of the MF wave transmission cones and increase the power densities of those waves at the DEMETER altitude. Citation: Lefeuvre F., J. L. Pinc¸n , and M. Parrot (2013), Midlatitude propagation of VLF to MF waves through nighttime ionosphere above powerful VLF transmitters
EMIC triggered chorus emissions in Cluster data

Electromagnetic ion cyclotron (EMIC) triggered chorus emissions have recently been a subject of several experimental, theoretical and simulation case studies, noting their similarities with whistler-mode chorus. We perform a survey of 8 years of Cluster data in order to increase the database of EMIC triggered emissions. The results of this is that EMIC triggered emissions have been unambiguously observed for only three different days. These three events are studied in detail. All cases have been observed at the plasmapause between 22 and 24 magnetic local time (MLT) and between − 15∘ and 15∘ magnetic latitude (λm). Triggered emissions are also observed for the first time below the local He+ gyrofrequency (fHe+). The number of events is too low to produce statistical results, nevertheless we point out a variety of common properties of those waves. The rising tones have a high level of coherence and the waves propagate away from the equatorial region. The propagation angle and degree of polarization are related to the distance from the equator, whereas the slope and the frequency extent vary from one event to the other. From the various spacecraft separations, we determine that the triggering process is a localized phenomenon in space and time. However, we are unable to determine the occurrence rates of these waves. Small frequency extent rising tones are more common than large ones. The newly reported EMIC triggered events are generally observed during periods of large AE index values and in time periods close to solar maximum
Simultaneous observations of quasi-periodic ELF/VLF wave emissions and electron precipitation by DEMETER satellite: A case study

International audience[1] We present results of case studies of quasi-periodic (QP) ELF/VLF hiss emissions detected onboard the DEMETER satellite. Three events with simultaneous periodic modulation in VLF wave intensity and energetic electron precipitation are found. In each event we observe exact coincidence of one or two busts of VLF wave intensity with energetic electron precipitation peaks. To our knowledge, such observations made onboard satellites have not been reported earlier. All events are observed at fairly quiet geomagnetic conditions (Kp < 3). The dynamic spectrum of the VLF waves in these QP events was characterized by a regular frequency increase in each burst, and the repetition period was less than or about 20 s. These features allow us to suggest that the observed events belong to the QP2-class, i.e., events which are not associated with geomagnetic pulsations. We also analyze energetic electron data from NOAA-17 spacecraft which has helio-synchronous circular orbit similar to DEMETER spacecraft and measured in the same region of the magnetosphere within 30 min for the analyzed events. NOAA-17 data confirm that the QP emissions were detected by DEMETER in the region of isotropization of energetic electrons, which is typically associated with the development of the cyclotron instability. Modulation of electron flux with a period close to the QP emission period is observed in two events. Based on the observed correlation between bursts of wave intensity and energetic particle flux, we estimate the location and spatial extent of the source region for QP emissions. Citation: Hayosh, M., D. L. Pasmanik, A. G. Demekhov, O. Santolik, M. Parrot, and E. E. Titova (2013), Simultaneous observations of quasi-periodic ELF/VLF wave emissions and electron precipitation by DEMETER satellite: A case study
Universal time control of AKR: Earth is a spin-modulated variable radio source

Auroral kilometric radiation (AKR) is known to be transient emissions generated by rapidly accelerated electrons together with sudden auroral activation in the polar magnetosphere. In contrast, the characteristics and relationship with the auroral acceleration of rather continuous AKR emissions are not well understood. We examine the emission using long-term data and report that the continuous AKR emission frequency changes with universal time (UT) as the Earth rotates, indicating that the Earth is a spin-modulated variable radio source. The observed UT variation of AKR frequency means that the acceleration altitude changes periodically with planetary rotation. The observations indicate that the diurnal wobble of the tilted geomagnetic field in the solar wind flow alters the magnetosphere-ionosphere (M-I) coupling state in the polar magnetosphere, giving rise to periodic variation of auroral particle acceleration altitude. These observations of planetary radio wave properties provide insight into the physics of planetary particle acceleration
Planetary period magnetic field oscillations in Saturn's magnetosphere: Postequinox abrupt nonmonotonic transitions to northern system dominance

We examine the “planetary period” magnetic field oscillations observed in the “core”\ud
region of Saturn’s magnetosphere (dipole L ≤ 12), on 56 near-equatorial Cassini periapsis\ud
passes that took place between vernal equinox in August 2009 and November 2012.\ud
Previous studies have shown that these consist of the sum of two oscillations related to the\ud
northern and southern polar regions having differing amplitudes and periods that had\ud
reached near-equal amplitudes and near-converged periods ~10.68 h in the interval to\ud
~1 year after equinox. The present analysis shows that an interval of strongly differing\ud
behavior then began ~1.5 years after equinox, in which abrupt changes in properties took\ud
place at ~6- to 8-month intervals, with three clear transitions occurring in February 2011,\ud
August 2011, and April 2012, respectively. These are characterized by large simultaneous\ud
changes in the amplitudes of the two systems, together with small changes in period about\ud
otherwise near-constant values of ~10.63 h for the northern system and ~10.69 h for the\ud
southern (thus, not reversed postequinox) and on occasion jumps in phase. The first\ud
transition produced a resumption of strong southern system dominance unexpected under\ud
northern spring conditions, while the second introduced comparably strong northern\ud
system dominance for the first time in these data. The third resulted in suppression of all\ud
core oscillations followed by re-emergence of both systems on a time scale of ~85 days,\ud
with the northern system remaining dominant but not as strongly as before. This behavior\ud
poses interesting questions for presently proposed theoretical scenarios.Work at Leicester was supported by STFC grant ST/H002480/1.Peer-reviewedPublisher Versio
Transient electron precipitation during oscillatory BBF braking: THEMIS observations and theoretical estimates

International audience[1] We use Time History of Events and Macroscale Interactions during Substorms (THEMIS) data acquired on 17 March 2008 between 10:22 and 10:32 UT to study the mechanism of transient electron injection into the loss cone during oscillatory bursty bulk flow (BBF) braking. During braking, transient regions of piled-up magnetic fluxes are formed. Perpendicular electron anisotropy observed in these regions (presumably caused by betatron perpendicular electron heating) may be a free-energy source of coexisting whistler waves. Parallel electrons with energies between 1 and 5 keV disappear inside these regions, and transient auroral forms (both rather discrete arcs and diffuse-like aurora around the arcs) are observed simultaneously by the ground all-sky imager at Fort Yukon. We use quasi-linear theory of electron resonant interaction with whistler waves and also estimate the effectiveness of electron nonlinear capture by strong whistler waves. We suggest that electron injection into the loss cone is caused by: (1) scattering by whistler waves and (2) parallel acceleration of electrons captured by stronger whistler waves
Microturbulence in the electron cyclotron frequency range at perpendicular supercritical shocks

International audienceSupercritical perpendicular collisionless shocks are characterized by a fraction of the incoming ions being reflected at the steep front. These reflected ions accumulate and form a foot, where the relative drift of the reflected ion beam versus the electrons can easily excite an electron cyclotron drift instability (ECDI). Here, we analyse the resulting wave emissions by two approaches. First, our linear dispersion analysis shows that several electron Bernstein harmonics can be unstable, their number being proportional to the drift, yet limited by the ion beam temperature. Second, the three local populations (incoming electrons/ions and reflected ions) of the foot region are introduced in full electromagnetic PIC periodic simulations in order to analyze the nonlinear regime of the ECDI. Main results are: (1) High gyro-harmonics develop over a short timescale less than the lower-hybrid period. (2) The spectral power shifts towards lower k-modes to accumulate on the first harmonic under the effects of two complementary processes: (i) trapping of the reflected ion beam, and (ii) resonance broadening. The latter acts to demagnetize the electrons in the dispersion relation. It initially applies to very high k-modes (kρe ≫ 1) and progressively, as time evolves, to lower k-modes, invalidating the existence of all gyro-harmonics, except the first one. (3) In the late stage a magnetic field component surprisingly develops in the energy spectrum that had so far been electrostatic. (4) The electrons are heated, which represents a source of preheating in the foot region of the shock front
Links between the plasmapause and the radiation belt boundaries as observed by the instruments CIS, RAPID, and WHISPER onboard Cluster

International audience[1] In the present work, we study the relations between the position of the plasmapause and the position of the radiation belt boundaries. The Cluster mission offers the exceptional opportunity to analyze those different regions of the inner magnetosphere with identical sensors on multiple spacecraft. We compare the positions of the radiation belt edges deduced from CIS (Cluster Ion Spectrometry) observations (electrons with energy > 2 MeV) with the positions of the plasmapause derived from WHISPER (Waves of HIgh frequency and Sounder for Probing of the Electron density by Relaxation) data (electron plasma frequency). In addition, we compare those results with the edges positions determined from RAPID (Research with Adaptive Particle Imaging Detectors) observations (electrons with energy between 244.1 and 406.5 keV). The period of 1 April 2007 to 31 March 2009 has been chosen for the analysis because at that time Cluster's perigee was located at lower radial distances than during the earlier part of the mission. The perigee was then as close as 2 R E , deep inside the plasmasphere and the radiation belts. This time period corresponds to a long solar activity minimum. Differences are observed between the radiation belt boundary positions obtained from the two different instruments: The radiation belt positions are related to the energy bands. The results show that the plasmapause position is more variable than the radiation belt boundary positions, especially during small geomagnetic activity enhancements. A correspondence is observed between the plasmapause position determined by WHISPER and the outer edge of the outer radiation belt of energetic electrons (> 2 MeV) observed by CIS. This result is unexpected since previous studies based on other spacecraft observations indicated a correlation between the inner edge of the outer belt and the plasmapause. However, during higher geomagnetic activity time periods, the plasmapause is located closer to the inner boundary of the outer radiation belt. Also, the thickness of the slot region is found to follow the global evolution of the geomagnetic activity. (2013), Links between the plasmapause and the radiation belt boundaries as observed by the instruments CIS, RAPID and WHISPER onboard Cluster