Publications

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Below, by year, are the publications listed in the HAL open archive.

2010

The Plasma Wave Investigation (PWI) onboard the BepiColombo/MMO: First measurement of electric fields, electromagnetic waves, and radio waves around Mercury
- Kasaba Y.
- Bougeret J.-L.
- Blomberg L. G.
- Kojima H.
- Yagitani S.
- Moncuquet M.
- Trotignon Jean-Gabriel
- Chanteur Gérard
- Kumamoto A.
- Kasahara Y.
- Lichtenberger J.
- Omura Y.
- Ishisaka K.
- Matsumoto H.
Planetary and Space Science, Elsevier, 2010, 58 (1-2), pp.238-278. The BepiColombo Mercury Magnetospheric Orbiter (MMO) spacecraft includes the plasma and radio wave observation system called Plasma Wave Investigation (PWI). Since the receivers for electric field, plasma waves, and radio waves are not installed in any of the preceding spacecraft to Mercury, the PWI will provide the first opportunity for conducting in-situ and remote-sensing observations of electric fields, plasma waves, and radio waves in the Hermean magnetosphere and exosphere. These observations are valuable in studying structure, dynamics, and energy exchange processes in the unique magnetosphere of Mercury. They are characterized by the key words of the non-MHD environment and the peculiar interaction between the relatively large planet without ionosphere and the solar wind with high dynamic pressure. The PWI consists of three sets of receivers (EWO, SORBET, and AM<sup>2</sup>P), connected to two sets of electric field sensors (MEFISTO and WPT) and two kinds of magnetic field sensors (LF-SC and DB-SC). The PWI will observe both waveforms and frequency spectra in the frequency range from DC to 10 MHz for the electric field and from 0.3 Hz to 640 kHz for the magnetic field. From 2008, we will start the development of the engineering model, which is conceptually consistent with the flight model design. The present paper discusses the significance and objectives of plasma/radio wave observations in the Hermean magnetosphere, and describes the PWI sensors, receivers and their performance as well as the onboard data processing. (10.1016/j.pss.2008.07.017)
DOI : 10.1016/j.pss.2008.07.017
MD simulations of GaN sputtering by Ar<SUP>+</SUP> ions : Ion-induced damage and near-surface modification under continuous bombardment
- Despiau-Pujo Emilie
- Chabert Pascal
Journal of Vacuum Science & Technology A, American Vacuum Society, 2010, 28 (5), pp.1105. Results from molecular dynamics simulations of continuous 50200 eV Ar bombardment on wurtzite and zinc blende GaN surfaces are reported. A new analytical bond-order potential, originally developed for growth process studies, is used to investigate the low-energy physical sputtering of GaN compounds. Preferential sputtering of N atoms is initially observed up to 3.5×1015 ions/cm2 fluence, after which the layers reach steady state sputtering. The crystalline structure of the GaN sample does not have a major influence on the sputtering yield due to the rapid amorphization of the top surface after a few hundred impacts. Concentration depth profiles indicate a surface enrichment in gallium with a N/Ga concentration ratio equal to 0.59±0.1 for 100 eV bombardment, in agreement with published experimental studies. For the same conditions, Ga, N, and GaN species represent 25, 60, and 7% of the sputtered products. A significant fraction of those products leave the surface with kinetic energies sufficiently high to damage the passivation layers on sidewalls during etching processes dominated by physical bombardment. (10.1116/1.3460904)
DOI : 10.1116/1.3460904
Particle transport in low core turbulence Tore-Supra plasmas
- Guirlet R.
- Sirinelli A.
- Parisot T.
- Sabot R.
- Artaud J.F.
- Bourdelle C.
- Garbet X.
- Hennequin Pascale
- Hoang G.T.
- Imbeaux Frédéric
- Segui J.-L.
- Mazon D.
- Villegas D.
Nuclear Fusion, IOP Publishing, 2010, 50, pp.095009. Electron and impurity transport has been studied in sawtoothing plasmas in the Tore-Supra tokamak. High time and space resolution measurements of the electron density reveal the existence of a flat profile region encompassing the q = 1 surface, on which is superimposed a density peak building up between sawtooth relaxations. For the first time in this regime, we have determined the underlying transport of both nickel and electrons independently of the effect of sawteeth in the central part of the plasma. Electron transport is consistent with the neoclassical expectations only in the close vicinity of the magnetic axis. Further out, it exceeds the neoclassical values as calculated with the NCLASS code, although the turbulence level is very low in the whole central region region. In contrast, nickel transport is in good agreement with the neoclassical calculations in the same region. The neoclassical effect on trapped particles of a persisting mode due to incomplete reconnection of the magnetic surfaces is consistent with these observations. (10.1088/0029-5515/50/9/095009)
DOI : 10.1088/0029-5515/50/9/095009
Three-dimensional structure of electron density fluctuations in the Hall thruster plasma: ExB mode
- Tsikata Sedina
- Honoré Cyrille
- Lemoine N.
- Grésillon D.
Physics of Plasmas, American Institute of Physics, 2010, 17, pp.112110. Collective scattering measurements have been conducted on the plasma of a Hall thruster, in which the electron density fluctuations are fully characterized by the dynamic form factor. The dynamic form factor amplitude distribution has been measured depending on the k-vector spatial and frequency components at different locations. Fluctuations are seen as propagating waves. The largest amplitude mode propagates nearly along the cross-field direction but at a phase velocity that is much smaller than the E×B drift velocity. Refined directional analysis of this largest amplitude mode shows a thin angular emission diagram with a mean direction that is not strictly along the E×B direction but at small angles near it. The deviation is oriented toward the anode in the (E,E×B) plane and toward the exterior of the thruster channel in the (B,E×B) plane. The density fluctuation rate is on the order of 1%. These experimentally determined directional fluctuation characteristics are discussed with regard to the linear kinetic theory model and particle-in-cell simulation results. (10.1063/1.3499350)
DOI : 10.1063/1.3499350
Whistler waves guided by density depletion ducts in a magnetoplasma
- Bakharev P. V.
- Zaboronkova T. M.
- Kudrin A. V.
- Krafft C.
Fizika Plazmy / Plasma Physics Reports, MAIK Nauka/Interperiodica, 2010, 36 (11), pp.919-930. The guided propagation of whistler waves along cylindrical density depletion ducts in a magneto-plasma is studied. It is shown that, under certain conditions, such ducts can support volume and surface eigenmodes. The dispersion properties and field structure of whistler modes guided by density depletion ducts are analyzed. The effect of collisional losses in the plasma on the properties of modes is discussed. (10.1134/S1063780X10110012)
DOI : 10.1134/S1063780X10110012
Ion dynamics during compression of Mercury's magnetosphere
- Delcourt Dominique C.
- Moore T. E.
- Fok M.-C. H.
Annales Geophysicae, European Geosciences Union, 2010, 28, pp.1467-1474. Because of the small planetary magnetic field as well as proximity to the Sun that leads to enhanced solar wind pressure as compared to Earth, the magnetosphere of Mercury is very dynamical and at times subjected to prominent compression. We investigate the dynamics of magnetospheric ions during such compression events. Using three-dimensional single-particle simulations, we show that the electric field induced by the time varying magnetic field can lead to significant ion energization, up to several hundreds of eVs or a few keVs. This energization occurs in a nonadiabatic manner, being characterized by large enhancements of the ion magnetic moment and bunching in gyration phase. It is obtained when the ion cyclotron period is comparable to the field variation time scale. This condition for nonadiabatic heating is realized in distinct regions of space for ions with different mass-to-charge ratios. During compression of Mercury's magnetosphere, heavy ions originating from the planetary exosphere may be subjected to such an abrupt energization, leading to loading of the magnetospheric lobes with energetic material. (10.5194/angeo-28-1467-2010)
DOI : 10.5194/angeo-28-1467-2010
Design of magnetic concentrators for high sensitivity anisotropic magnetoresistor devices
- Mansour Malik
- Coillot Christophe
- Chanteur Gérard
- Roux A.
- Nguyen van Dau Frédéric
Journal of Applied Physics, American Institute of Physics, 2010, 107, pp.09E707. In this work, a very promising shape of magnetic concentrators taking advantage of the symmetrical flux leakage of Mn-Zn ferrite magnetic cores is presented. This configuration consists of two ferromagnetic rods separated by two air gaps allowing to place anisotropic magnetoresistance sensors in the core axis. Results from three-dimensional finite elements modeling are presented. We show that an appropriate shape optimization of core extremities enables to improve significantly the amplification factor without any increase in length. (10.1063/1.3337747)
DOI : 10.1063/1.3337747
Global response to local ionospheric mass ejection
- Moore T. E.
- Fok M.-C. H.
- Delcourt Dominique C.
- Slinker Steve P.
- Fedder Joel A.
Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2010, 115 (A12). We revisit a reported "Ionospheric Mass Ejection" using prior event observations to guide a global simulation of local ionospheric outflows, global magnetospheric circulation, and plasma sheet pressurization, and comparing our results with the observed global response. Our simulation framework is based on test particle motions in the Lyon-Fedder-Mobarry (LFM) global circulation model electromagnetic fields. The inner magnetosphere is simulated with the Comprehensive Ring Current Model (CRCM) of Fok and Wolf, driven by the transpolar potential developed by the LFM magnetosphere, and includes an embedded plasmaspheric simulation. Global circulation is stimulated using the observed solar wind conditions for the period 24-25 September 1998. This period begins with the arrival of a Coronal Mass Ejection, initially with northward, but later with southward interplanetary magnetic field. Test particles are launched from the ionosphere with fluxes specified by local empirical relationships of outflow to electrodynamic and particle precipitation imposed by the MHD simulation. Particles are tracked until they are lost from the system downstream or into the atmosphere, using the full equations of motion. Results are compared with the observed ring current and a simulation of polar and auroral wind outflows driven globally by solar wind dynamic pressure. We find good quantitative agreement with the observed ring current, and reasonable qualitative agreement with earlier simulation results, suggesting that the solar wind driven global simulation generates realistic energy dissipation in the ionosphere and that the Strangeway relations provide a realistic local outflow description. (10.1029/2010JA015640)
DOI : 10.1029/2010JA015640
Design criteria and validation of a vacuum load current multiplier on a mega-ampere microsecond inductive storage generator
- Chuvatin Alexandre S.
- Kim A. A.
- Kokshenev V. A.
- Kovalchuk Boris M.
- Lassalle Francis
- Calamy Hervé
- Krishnan M.
Laser and Particle Beams, Cambridge University Press (CUP), 2010, 28 (3), pp.361-369. The load current multiplier concept (LCM) was suggested for improving the energy transfer efficiency from pulse power generators to loads. The concept was initially demonstrated at atmospheric pressure and dielectric insulation on a compact, 100 kA, microsecond capacitor bank. This paper reports on the LCM design criteria for mega-ampere vacuum pulse power when the LCM comprises a large-inductance magnetic flux extruder cavity without a magnetic core. The analytical and numerical design approach presented was experimentally validated on GIT12 mega-ampere inductive energy storage generator with a constant-inductance load. The LCM technique increased the peak load current from typically 4.6 MA at 1.87 µs on this generator, to 6.43 MA at 2.0 µs. The electromagnetic power into a ~10 nH load increased from 100 GW to 230 GW. This result is in good agreement with the presented numerical simulations and it corresponds to a 95% increase of the achievable magnetic pressure at 8 cm radius in the load. The compact, LCM hardware allows the GIT12 generator to operate more efficiently without modifying the stored energy or architecture. The demonstrated load power and energy increase using the LCM concept is of importance for further studies on power amplification in vacuum and high energy density physics. (10.1017/S0263034610000224)
DOI : 10.1017/S0263034610000224
Three dimensional anisotropic k-spectra of turbulence at sub-proton scales in the solar wind
- Sahraoui Fouad
- Goldstein M.L.
- Belmont Gérard
- Canu Patrick
- Rezeau Laurence
Physical Review Letters, American Physical Society, 2010 (105), pp.131101. We show the first three dimensional (3D) dispersion relations and k spectra of magnetic turbulence in the solar wind at subproton scales. We used the Cluster data with short separations and applied the k-filtering technique to the frequency range where the transition to subproton scales occurs. We show that the cascade is carried by highly oblique kinetic Alfve´n waves with !plas 0:1!ci down to k?i 2. Each k spectrum in the direction perpendicular to B0 shows two scaling ranges separated by a breakpoint (in the interval ½0:4; 1k?i): a Kolmogorov scaling k1:7 ? followed by a steeper scaling k4:5 ? . We conjecture that the turbulence undergoes a transition range, where part of the energy is dissipated into proton heating via Landau damping and the remaining energy cascades down to electron scales where electron Landau damping may predominate. (10.1103/PhysRevLett.105.131101)
DOI : 10.1103/PhysRevLett.105.131101
Surface loss rates of H and Cl atoms in an inductively coupled plasma etcher using time-resolved electron density and optical emission measurements
- Curley G. A.
- Gatilova L.
- Guilet S.
- Bouchoule S.
- Gogna G. S.
- Sirse Nishant
- Karkari S.
- Booth Jean-Paul
Journal of Vacuum Science & Technology A, American Vacuum Society, 2010, 28 (2), pp.360-372. A study is undertaken of the loss kinetics of H and Cl atoms in an inductively coupled plasma (ICP) reactor used for the etching of III-V semiconductor materials. A time-resolved optical emission spectroscopy technique, also referred to as pulsed induced fluorescence (PIF), has been combined with time-resolved microwave hairpin probe measurements of the electron density in a pulsed Cl2/H2-based discharge for this purpose. The surface loss rate of H, kwH, was measured in H2 plasma and was found to lie in the 125500 s−1 range (γH surface recombination coefficient of ∼ 0.0060.023), depending on the reactor walls conditioning. The PIF technique was then evaluated for the derivation of kwCl, and γCl in Cl2-based plasmas. In contrast to H2 plasma, significant variations in the electron density may occur over the millisecond time scale corresponding to Cl2 dissociation at the rising edge of the plasma pulse. By comparing the temporal evolution of the electron density and the Ar-line intensity curves with 10% of Ar added in the discharge, the authors show that a time-resolved actinometry procedure using Ar as an actinometer is valid at low to moderate ICP powers to estimate the Cl loss rate. They measured a Cl loss rate of ∼ 125200 s−1 (0.03 ≤ γCl ≤ 0.06) at 150 W ICP power for a reactor state close to etching conditions. The Cl surface loss rate was also estimated for high ICP power (800 W) following the same procedure, giving a value of ∼ 130150 s−1 (γCl ∼ 0.04), which is close to that measured at 150 W ICP power. (10.1116/1.3330766)
DOI : 10.1116/1.3330766
Simultaneous FAST and Double Star TC1 observations of broadband electrons during a storm time substorm
- Nakajima A.
- Shiokawa K.
- Seki K.
- Nakamura R.
- Keika K.
- Baumjohann W.
- Takada T.
- Mcfadden J. P.
- Carlson C. W.
- Fazakerley A.
- Rème H.
- Dandouras I.
- Strangeway R. J.
- Le Contel Olivier
- Cornilleau-Wehrlin Nicole
- Yearby K. H.
Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2010, 115, pp.7217. Broadband electrons (BBEs) exhibit remarkable electron flux enhancements over a broad energy range (0.03-30 keV) near the equatorward edge of the auroral oval during geomagnetic storms. Here, we report a BBE event observed by the Fast Auroral Snapshot (FAST) satellite at 1355-1359 UT, 61°-66° invariant latitudes, 0600 magnetic local time (MLT), and 3800 km altitude during a storm on 25 July 2004. The Double Star (DS) TC1 satellite was located near the magnetic equator at L = 5.7, close to the same local time as FAST. We investigate the acceleration process of BBEs from the inner magnetosphere to near the ionosphere by comparing electron data obtained by FAST and DS TC1. We also investigate both plasma and field variations in the inner magnetosphere associated with substorm onset using DS TC1 data to examine the relationship between the BBEs and the storm time substorm. Ground geomagnetic field data show a positive H-bay at 1349 UT at 0600 MLT, indicating that a storm time substorm started just before the appearance of the BBEs. At 1350 UT, a tailward ion flow was observed by DS TC1. Then, DS TC1 observed a local dipolarization and a drastic ion density enhancement at 1351 UT, indicating that particle heating associated with the substorm was occurring in the inner magnetosphere. From 1352 UT, electron fluxes were isotropically enhanced at energies above 0.5 keV as observed by DS TC1. On the other hand, the pitch angle distribution of BBEs at the FAST altitude showed field-aligned lower-energy electrons below 0.5 keV and isotropic higher-energy electrons above 0.5 keV. From these data, it was inferred that the BBEs might consist of two energy components due to the acceleration or heating of electrons at different altitudes in association with the storm time substorm. (10.1029/2009JA014907)
DOI : 10.1029/2009JA014907
Bilan et Perspective 2006 - 2009, Programme National Soleil Terre
- Fontaine Dominique
- Vilmer N.
, 2010.
Bepi-Colombo : Mercury Exploration
- Chanteur Gérard
Flash X - La revue scientifique de l'Ecole polytechnique, Ecole polytechnique, 2010, 12, pp.32-33. ISSN : 1775-0385
Plasmas Naturels : Le Programme National Soleil - Terre
- Fontaine Dominique
Flash X - La revue scientifique de l'Ecole polytechnique, Ecole polytechnique, 2010, 12, pp.27-31. ISSN : 1775-0385
Plasmas froids
- Booth Jean-Paul
- Chabert Pascal
Flash X - La revue scientifique de l'Ecole polytechnique, Ecole polytechnique, 2010, 12, pp.3-5. ISSN : 1775-0385
Plasma assisted ignition and combustion
- Starikovskaia Svetlana
- Starikovskii A.Yu.
, 2010, pp.71-93.
Modelling of an afterglow plasma in air produced by a pulsed discharge
- Pintassilgo C.D.
- Guerra V.
- Guaitella Olivier
- Rousseau Antoine
Plasma Sources Science and Technology, IOP Publishing, 2010, 19, pp.055001. A kinetic model is developed to study the afterglow plasma of a pulsed discharge in air. This model includes a detailed analysis of the temporal evolution of heavy species during the pulse, followed by their relaxation in the afterglow. The predicted results are compared with two experimental sets performed in the time afterglow of a pulsed discharge in N220%O2 at a pressure p = 133 Pa involving the measurements of (i) N2(B) and N2(C) fluorescences for a discharge current I = 40 mA and a pulse duration τ = 200 µs and 10 ms, together with (ii) the absolute concentration of NO(X) for I = 40 and 80 mA with τ varying from 1 to 4 ms. The results of the model agree reasonably well with the measurements of N2(B) and N2(C) decays. It is shown that under these experimental conditions, N2(B) is always populated mainly via the process N2(A) N2(X, 5 ≤ v ≤ 14) → N2(B) N2(X, v = 0), while the relaxation of N2(C) is dominated by the pooling reaction N2(A) N2(A) → N2(C) N2(X, v = 0). An almost constant concentration of NO(X) is experimentally observed until the remote afterglow, but the present model is only capable of predicting the same order of magnitude for afterglow times t 0.05 s. Several hypotheses are discussed and advanced in order to explain this discrepancy. (10.1088/0963-0252/19/5/055001)
DOI : 10.1088/0963-0252/19/5/055001
Planar Wire-Array Z-Pinch Implosion Dynamics and X-Ray Scaling at Multiple-MA Drive Currents for a Compact Multisource Hohlraum Configuration
- Jones B.
- Ampleford D. J.
- Vesey R. A.
- Cuneo Michael E.
- Coverdale C. A.
- Waisman E. M.
- Jones M. C.
- Fowler W. E.
- Stygar W. A.
- Serrano J. D.
- Vigil M. P.
- Esaulov A. A.
- Kantsyrev Viktor L.
- Safronova Alla S.
- Williamson Kenneth M.
- Chuvatin Alexandre S.
- Rudakov Leonid I.
Physical Review Letters, American Physical Society, 2010, 104 (12), pp.125001. An indirect drive configuration is proposed wherein multiple compact Z-pinch x-ray sources surround a secondary hohlraum. Planar compact wire arrays allow reduced primary hohlraum surface area compared to cylindrical loads. Implosions of planar arrays are studied at up to 15 TW x-ray power on Saturn with radiated yields exceeding the calculated kinetic energy, suggesting other heating paths. X-ray power and yield scaling studied from 16 MA motivates viewfactor modeling of four 6-MA planar arrays producing 90 eV radiation temperature in a secondary hohlraum. (10.1103/PhysRevLett.104.125001)
DOI : 10.1103/PhysRevLett.104.125001
Nonlinear fan instability of electromagnetic waves
- Krafft C.
- Volokitin A.
Physics of Plasmas, American Institute of Physics, 2010, 17, pp.102303. This paper studies the linear and nonlinear stages of the fan instability, considering electromagnetic waves of the whistler frequency range interacting resonantly with energetic electron fluxes in magnetized plasmas. The main attention is paid to determine the wave-particle interaction processes that can lead to the excitation of intense electromagnetic waves by nonequilibrium particle distributions involving suprathermal tails, and to explain under what conditions and through what mechanisms they can occur, develop, and saturate. This paper presents and discusses two main processes: (i) the linear fan instability and (ii) the nonlinear process of dynamical resonance merging, which can significantly amplify the energy carried by linearly destabilized waves after they saturate due to particle trapping. This study consists of (i) determining analytically and numerically, for parameters typical of space and laboratory plasmas, the linear growth rates of whistlers excited by suprathermal particle fluxes through the fan instability, as well as the corresponding thresholds and the physical conditions at which the instability can appear, (ii) building a theoretical self-consistent 3D model and a related numerical code for describing the nonlinear evolution of the wave-particle system, and (iii) performing numerical simulations to reveal and characterize the nonlinear amplification process at work, its conditions of development, and its consequences, notably in terms of electromagnetic wave radiation. The simulations show that when the waves have reached sufficient energy levels owing to the linear fan instability, they saturate by trapping particles and due to the complex dynamics of these particles in the electromagnetic fields, the resonant velocities' domains of the waves overlap and merge, meanwhile a strong increase of the wave energy occurs. (10.1063/1.3479829)
DOI : 10.1063/1.3479829
Quantum Cascade Laser Absorption Spectroscopy - a New Method to Study Molecular Plasma Components
- Röpcke J.
- Glitsch S.
- Davies P.B.
- Hempel F.
- Lang N.
- Rousseau Antoine
- Wege S.
- Welzel S.
Journal of Physics: Conference Series, IOP Science, 2010, 227, pp.012005. The recent development of quantum cascade lasers (QCLs) offers an attractive new option for the monitoring and control of industrial plasma processes and for trace-gas analysis as well as for highly time-resolved studies on the kinetics of plasma processes. The contribution reviews selected examples of the application of QCLs for infrared absorption studies in basic research and for plasma monitoring and control in industry. (10.1088/1742-6596/227/1/012005)
DOI : 10.1088/1742-6596/227/1/012005
Plasmas de Fusion Magnétique
- Hennequin Pascale
Flash X - La revue scientifique de l'Ecole polytechnique, Ecole polytechnique, 2010, 12, pp.25-26. ISSN : 1775-0385
Formation of a sodium ring in Mercury's magnetosphere
- Yagi Manabu
- Seki K.
- Matsumoto Y.
- Delcourt Dominique C.
- Leblanc François
Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2010, 115 (A10), pp.A10253. We have performed a statistical analysis of exospheric sodium ion paths in Mercury's magnetosphere under northward interplanetary magnetic field conditions. Electric and magnetic field models used in the simulation were obtained from a global MHD simulation model, whereas the initial conditions of test Na+ ions were derived from a sodium exosphere model. We observe the formation of a ring-shaped high-pressure region consisting of energetic sodium ions traveling around the planet close to the equatorial plane. The configuration of this "sodium ring" as well as the acceleration processes leading to its formation strongly depend on the solar wind conditions. When the dynamic pressure is low, most of the Na+ are picked up in the magnetosphere and accelerated by the large-scale convective electric field. In contrast, in the case of high dynamic pressure, ions that are picked up in the magnetosheath and penetrate into the magnetosphere significantly contribute to the sodium ring. The configuration of this ring also depends upon the intensity of the solar wind electric field. Our analysis reveals that the pressure built by the Na+ ions may be significant as compared to the MHD pressure around the planet. (10.1029/2009JA015226)
DOI : 10.1029/2009JA015226
Non adiabatic electron behavior through a supercritical perpendicular collisionless shock: Impact of the shock front turbulence
- Savoini Philippe
- Lembège Bertrand
Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2010, 115 (A11), pp.A11103. Adiabatic and nonadiabatic electrons transmitted through a supercritical perpendicular shock wave are analyzed with the help of test particle simulations based on field components issued from 2 − D full-particle simulation. A previous analysis (Savoini et al., 2005) based on 1 − D shock profile, including mainly a ramp (no apparent foot) and defined at a fixed time, has identified three distinct electron populations: adiabatic, overadiabatic, and underadiabatic, respectively, identified by μds/μus ≈ 1, >1 and <1, where μus and μds are the magnetic momenta in the upstream and downstream regions. Presently, this study is extended by investigating the impact of the time evolution of 2 − D shock front dynamics on these three populations. Analysis of individual time particle trajectories is performed and completed by statistics based on the use of different upstream velocity distributions (spherical shell of radius vshell and a Maxwellian with thermal velocity vthe). In all statistics, the three electron populations are clearly recovered. Two types of shock front nonstationarity are analyzed. First, the impact of the nonstationarity along the shock normal (due to the front self-reformation only) strongly depends on the values of vshell or vthe. For low values, the percentages of adiabatic and overadiabatic electrons are almost comparable but become anticorrelated under the filtering impact of the self-reformation; the percentage of the underadiabatic population remains almost unchanged. In contrast, for large values, this impact becomes negligible and the adiabatic population alone becomes dominant. Second, when 2 − D nonstationarity effects along the shock front (moving rippling) are fully included, all three populations are strongly diffused, leading to a larger heating; the overadiabatic population becomes largely dominant (and even larger than the adiabatic one) and mainly contributes to the energy spectrum. (10.1029/2010JA015381)
DOI : 10.1029/2010JA015381
Chorus source region localization in the Earth's outer magnetosphere using THEMIS measurements
- Agapitov O
- Krasnoselskikh V
- Zaliznyak Yu
- Angelopoulos V
- Le Contel Olivier
- Rolland G
Annales Geophysicae, European Geosciences Union, 2010, 28, pp.1377–1386. Discrete ELF/VLF chorus emissions, the most intense electromagnetic plasma waves observed in the Earth's radiation belts and outer magnetosphere, are thought to propagate roughly along magnetic field lines from a localized source region near the magnetic equator towards the magnetic poles. THEMIS project Electric Field Instrument (EFI) and Search Coil Magnetometer (SCM) measurements were used to determine the spatial scale of the chorus source lo-calization region on the day side of the Earth's outer magne-tosphere. We present simultaneous observations of the same chorus elements registered onboard several THEMIS spacecraft in 2007 when all the spacecraft were in the same orbit. Discrete chorus elements were observed at 0.15–0.25 of the local electron gyrofrequency, which is typical for the outer magnetosphere. We evaluated the Poynting flux and wave vector distribution and obtained chorus wave packet quasi-parallel propagation to the local magnetic field. Amplitude and phase correlation data analysis allowed us to estimate the characteristic spatial correlation scale transverse to the local magnetic field to be in the 2800–3200 km range. Keywords. Electromagnetics (Random media and rough surfaces) – Magnetospheric physics (Plasma waves and in-stabilities) – Radio science (Remote sensing) (10.5194/angeo-28-1377-2010)
DOI : 10.5194/angeo-28-1377-2010

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