Publications

2010

• Evidence for surface oxidation on Pyrex of NO into NO<SUB>2</SUB> by adsorbed O atoms
  
  • Guaitella Olivier
  • Hübner M.
  • Welzel S.
  • Marinov Daniil
  • Röpcke J.
  • Rousseau Antoine
  Plasma Sources Science and Technology, IOP Publishing, 2010, 19, pp.045026. The surface of a Pyrex discharge tube was treated by a capacitively coupled RF plasma at low pressure. In cases where the plasma contained oxygen, O atoms deposition on the tube surface could be confirmed via the time-dependent conversion of NO to NO2 in a post-plasma experiment. Inside the discharge tube, the evolution of the concentrations of NO and of NO2 was measured using quantum cascade laser absorption spectroscopy in the mid-infrared spectral range. The surface density of atomic oxygen was estimated to be about 2 × 1014&#8201;cm&#8722;2 based on NO oxidation in the closed reactor. The production rate of NO2 is in the range of 2 × 1011&#8201;molecules&#8201;cm&#8722;3&#8201;s&#8722;1. (10.1088/0963-0252/19/4/045026)
  DOI : 10.1088/0963-0252/19/4/045026
• On the Boltzmann relation in a cold magnetized plasma
  
  • Nasi L.
  • Raimbault Jean-Luc
  Physics of Plasmas, American Institute of Physics, 2010, 17, pp.113513. A systematic and exact comparison between the forces acting on magnetized electrons in a current-free plasma is considered within a fluid model. We show that the Boltzmann relation is fulfilled in the drift-diffusion approximation when (hi/he)(1 he2)/(1 hi2)&#10913;1 where he (or hi) is the ratio of the electron (or ion) cyclotron to the collision frequency. When the nonlinear inertia terms are taken into account, the previous criterion is too rough and must be modified. In particular it is proved that the Boltzmann relation is not uniformly valid in the plasma. The case of bounded plasmas where the electron temperature must be determined self-consistently is discussed in detail. (10.1063/1.3517174)
  DOI : 10.1063/1.3517174
• A model for the self-pulsing regime of microhollow cathode discharges
  
  • Chabert Pascal
  • Lazzaroni Claudia
  • Rousseau Antoine
  Journal of Applied Physics, American Institute of Physics, 2010, 108, pp.113307. Microhollow cathode discharges may operate in different regimes depending of the discharge current. They are subject to relaxation oscillations in the so-called self-pulsing regime in which the discharge oscillates between two quasiequilibria: at low current it remains confined in the microhole whereas it expands on the cathode backside during short high-current pulses. A model based on a nonlinear discharge resistance is proposed to describe the phenomenon. The analysis of the dynamics reveals that the current pulse rises in an extremely short time while the characteristic (longer) decay time is imposed by the resistance when the discharge is expanded outside the hole. It is shown how the nonlinear discharge resistance may be inferred from the experimental current-voltage signals. (10.1063/1.3518533)
  DOI : 10.1063/1.3518533
• Determination of the averaged charge-to-mass ratio of the heavy charged constituents of a magnetoplasma using whistler wave measurements
  
  • Krafft C.
  • Lundin B. V.
  Annales Geophysicae, European Geosciences Union, 2010, 28, pp.2237-2247. In a cold magnetized plasma with two light ions of comparable gyrofrequencies and any species of heavy ions and/or charged dust particulates, a technique is developed to recover the relative charge density of the heavy plasma population and to estimate its effective averaged charge-to-mass ratio. Such results can be obtained without using mass spectrometer data but only the measurements of the ion plasma frequency, the electron gyro- and plasma frequencies as well as the two highest ion cutoff frequencies. (10.5194/angeo-28-2237-2010)
  DOI : 10.5194/angeo-28-2237-2010
• Comparison of the use of SQUID an Hall effect sensors in NDE
  
  • Bettaieb L.
  • Kokabi H.
  • Poloujadoff M.
  • Sentz A.
  • Krause H. J
  • Coillot Christophe
  Materials Evaluation, American Society for Nondestructive Testing, 2010, 68 (5), pp.535-554. ...
• Measurements of stray antenna capacitance in the STEREO/WAVES instrument: Comparison of the measured voltage spectrum with an antenna electron shot noise model
  
  • Zouganelis I.
  • Maksimovic M.
  • Meyer-Vernet N.
  • Bale S. D.
  • Eastwood Jonathan P.
  • Zaslavsky A.
  • Dekkali M.
  • Goetz K.
  • Kaiser M. L.
  Radio Science, American Geophysical Union, 2010, 45, pp.1005. One of the most accurate techniques for in situ measuring the electron density and temperature in space plasmas is the quasi-thermal noise spectroscopy, which uses the voltage fluctuation spectrum on an electric antenna. This technique has been used successfully on the WIND and ULYSSES spacecraft; however, on STEREO this technique may only work in high-density filamentary structures, where the Debye length is small, because the STEREO/WAVES antennas have a large surface area, so that the resulting shot noise spectrum in the solar wind dominates the power at lower frequencies. In the unperturbed solar wind, we can use instead the electron shot noise to infer the plasma density. For doing so, we use well calibrated WIND particle data to deduce the stray capacitance of the STEREO/WAVES antenna system in a special configuration when the STEREO-B spacecraft was just downstream of WIND. This stray capacitance is also compared to ground experiments done on the flight spare equipment and independent calibrations performed using the galactic radio background. (10.1029/2009RS004194)
  DOI : 10.1029/2009RS004194
• Cluster observations of outflowing electron distributions and broadband electrostatic emissions above the polar cap
  
  • Teste A.
  • Fontaine Dominique
  • Canu Patrick
  • Belmont Gérard
  Geophysical Research Letters, American Geophysical Union, 2010, 37, pp.3103. We investigate the excellent correlation between ionospheric upgoing electron beams and broadband electrostatic emissions (0-6 kHz) observed by Cluster, at 5 to 9 Earth's radii above the polar cap. In the absence of detailed, high time resolution waveform data in that region, we precisely analyzed several electron beams to obtain information concerning wave-particle interactions. Our results indicate that these beams are extremely variable and occasionally show multiple components. The processes involved might then occur on very short time scales, of the order of or shorter than sampling rates, typically 100 ms. We suggest that non linearities are at the origin of the spread of the frequency range of the waves simultaneously observed, as well as of the beam variability. We conclude that these electron beams are likely to destabilize Langmuir waves and, by the non-linear evolution of the electron bump-on-tail instability, could be responsible for the appearance of electrostatic solitary waves above the polar cap. (10.1029/2009GL041593)
  DOI : 10.1029/2009GL041593
• Solar wind turbulent spectrum from MHD to electron scales
  
  • Alexandrova O.
  • Saur J.
  • Lacombe C.
  • Mangeney A.
  • Schwartz S. J.
  • Mitchell J.
  • Grappin Roland
  • Robert Patrick
  , 2010, 1216, pp.144-147. Turbulent spectra of magnetic fluctuations in the free solar wind are studied from MHD to electron scales using Cluster observations. We discuss the problem of the instrumental noise and its influence on the measurements at the electron scales. We confirm the presence of a curvature of the spectrum ~expkrho<SUB>e</SUB> over the broad frequency range ~ [10,100] Hz, indicating the presence of a dissipation. Analysis of seven spectra under different plasma conditions show clearly the presence of a quasi-universal power-law spectrum at MHD and ion scales. However, the transition from the inertial range ~k<SUP>-1.7</SUP> to the spectrum at ion scales ~k<SUP>-2.7</SUP> is not universal. Finally, we discuss the role of different kinetic plasma scales on the spectral shape, considering normalized dimensionless spectra. (10.1063/1.3395821)
  DOI : 10.1063/1.3395821
• Simulations of radical and ion fluxes on wafer in a Cl<SUB>2</SUB>/Ar ICP discharge : Confrontation with GaAs and GaN etch experiments
  
  • Despiau-Pujo Emilie
  • Chabert Pascal
  • Bansropun S.
  • Thenot D.
  • Plouhinec P.
  • Cassette S.
  Journal of Vacuum Science and Technology, American Vacuum Society (AVS), 2010, 28 (4), pp.693. A two-dimensional fluid model is used to study an industrial Ar/Cl<SUB>2</SUB> inductively coupled plasma discharge designed to etch III-V samples. The effect of rf power, gas pressure, and chlorine content on the fluxes of reactive species reaching the wafer is numerically investigated. To understand how the etch process is influenced by the discharge conditions, simulation results are confronted with GaAs and GaN etch experiments performed in the same reactor geometry. When the source power is increased, the measured etch rate increase is consistent with the Cl radical and ion fluxes increase shown in the simulation, as well as the ion energy decrease due to the constant value of the wafer-holder power. Increasing the gas pressure results in a moderate increase in the etch rate due to the lower magnitude, lower mean energy, and anisotropy of the ion flux at high pressure. When the chlorine content is increased, the total ion flux decreases while Cl and Cl2 neutral fluxes increase significantly. A good correlation is obtained between calculated fluxes and etch characteristics, analyzed with scanning electron microscope images of etch profiles. (10.1116/1.3437492)
  DOI : 10.1116/1.3437492
• Electron drift velocity in SF<SUB>6</SUB> in strong electric fields determined from rf breakdown curves
  
  • Lisovskiy V.
  • Yegorenkov V.
  • Booth Jean-Paul
  • Landry K.
  • Douai D.
  • Cassagne V.
  Journal of Physics D: Applied Physics, IOP Publishing, 2010, 43, pp.385203. This paper presents measurements of the electron drift velocity Vdr in SF6 gas for high reduced electric fields (E/N = 3305655&#8201;Td (1&#8201;Td = 10e&#8722;17&#8201;V&#8201;cm2)). The drift velocities were obtained using the method of Lisovskiy and Yegorenkov (1998 J. Phys. D: Appl. Phys. 31 3349) based on the determination of the pressure and voltage of the turning points of rf capacitive discharge breakdown curves for a range of electrode spacings. The Vdr values thus obtained were in good agreement with those calculated from the cross-sections of Phelps and Van Brunt (1988 J. Appl. Phys. 64 4269) using the BOLSIG code. The validity of the LisovskiyYegorenkov method is discussed and we show that it is applicable over the entire E/N range where rf discharge ignition at breakdown occurs for rf frequencies of 13.56&#8201;MHz or above. (10.1088/0022-3727/43/38/385203)
  DOI : 10.1088/0022-3727/43/38/385203
• On the efficiency of intrinsic rotation generation in tokamaks
  
  • Kosuga Y.
  • Diamond P.H.
  • Gürcan Özgür D.
  Physics of Plasmas, American Institute of Physics, 2010, 17, pp.102313. A theory of the efficiency of the plasma flow generation process is presented. A measure of the efficiency of plasma self-acceleration of mesoscale and mean flows from the heat flux is introduced by analogy with engines, using the entropy budget defined by thermal relaxation and flow generation. The efficiency is defined as the ratio of the entropy destruction rate due to flow generation to the entropy production rate due to &#8711;T relaxation (i.e., related to turbulent heat flux). The efficiencies for two different cases, i.e., for the generation of turbulent driven E×B shear flow (zonal flow) and for toroidal intrinsic rotation, are considered for a stationary state, achieved by balancing entropy production rate and destruction rate order by order in O(k&#8741;/k&#8869;), where k is the wave number. The efficiency of intrinsic toroidal rotation is derived and shown to be eIR&#8764;(Mach)2th&#8764;0.01. The scaling of the efficiency of intrinsic rotation generation is also derived and shown to be &#961;2&#8727;(q2/s2)(R2/L2T)=&#961;2&#8727;(L2s/L2T), which suggests a machine size scaling and an unfavorable plasma current scaling which enters through the shear length. (10.1063/1.3496055)
  DOI : 10.1063/1.3496055
• Correction to 'Simulation of electric field and current during the 11 June 1993 disturbance dynamo event: Comparison with the observations
  
  • Zaka K. Z.
  • Kobea A. T.
  • Doumbia V.
  • Richmond A. D.
  • Maute A.
  • Mene N. M.
  • Obrou O. K.
  • Assamoi P.
  • Boka K.
  • Adohi J.-P.
  • Amory-Mazaudier Christine
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2010, 115 (A12), pp.A12314. Not Available (10.1029/2010JA016292)
  DOI : 10.1029/2010JA016292
• Scaling and anisotropy in magnetohydrodynamic turbulence in a strong mean magnetic field
  
  • Grappin Roland
  • Müller Wolf-Christian
  Physical Review E, American Physical Society (APS), 2010, 82 (2), pp.26406. We present an analysis of the anisotropic spectral energy distribution in incompressible magnetohydrodynamic turbulence permeated by a strong mean magnetic field. The turbulent flow is generated by high-resolution pseudospectral direct numerical simulations with large-scale isotropic forcing. Examining the radial energy distribution for various angles &#952; with respect to B0 reveals a specific structure which remains hidden when not taking axial symmetry with respect to B0 into account. For each direction, starting at the forced large scales, the spectrum first exhibits an amplitude drop around a wave number k0 which marks the start of a scaling range and goes on up to a dissipative wave number kd(&#952;). The three-dimensional spectrum for k&#8805;k0 is described by a single &#952;-independent functional form F(k/kd), with the scaling law being the same in every direction. The previous properties still hold when increasing the mean field from B0=5 up to B0=10brms, as well as when passing from resistive to ideal flows. We conjecture that at fixed B0 the direction-independent scaling regime is reached when increasing the Reynolds number above a threshold which raises with increasing B0. Below that threshold critically balanced turbulence is expected. (10.1103/PhysRevE.82.026406)
  DOI : 10.1103/PhysRevE.82.026406
• Extraction and acceleration of ions from an ion-ion plasma
  
  • Popelier Lara
  • Aanesland Ane
  • Chabert Pascal
  AIP Conference Proceedings, American Institute of Physics, 2010, 1390, pp.688-674. Extraction and acceleration of positive and negative ions from a strong electronegative plasma and from an ion&#8208;ion plasma is investigated in the PEGASES thruster, working with SF6. The plasma is generated in a cylindrical quartz tube terminated by metallic endplates. The electrons are confined by a static magnetic field along the axis of the cylinder. The electron mobility along the field is high and the electrons are determining the sheaths in front of the endplates. The core plasma potential can therefore be controlled by the bias applied to the endplates. An ion&#8208;ion plasma forms at the periphery as a result of electron confinement and ions can freely diffuse along the perpendicular direction or extraction axis. Langmuir probe and RFEA measurements are carried out along this axis. The measured ion energy distributions shows a single peak centered around a potential consistent with the plasma potential and the peak position could be controlled with a positive voltage applied to the endplates. When the endplates are biased negatively, the plasma potential saturates and remained close to 15 V. A beam of negatively charged particles can be observed under certain conditions when the endplates were biased negatively. (10.1063/1.3637439)
  DOI : 10.1063/1.3637439
• Low energy Ar<SUP>+</SUP> bombardment of GaN surfaces : A statistical study of ion reflection and sputtering
  
  • Despiau-Pujo Emilie
  • Chabert Pascal
  Journal of Vacuum Science & Technology A, American Vacuum Society, 2010, 28 (5), pp.1263. Statistical molecular dynamics simulations are performed to analyze the sputtering of w-GaN (wurtzite) and z-GaN (zinc blende) surfaces under 100 eV Ar ion bombardment. Ion reflection and physical sputtering mechanisms are investigated as a function of the ion impact angle and the crystalline nature of samples. The probability of ion reflection is lower for the w-GaN phase and increases with the angle of incidence &#952;i. As &#952;i becomes more glancing, the reflected ions become more energetic and their angular distribution tends to narrow. The sputtering yields of w-GaN and z-GaN surfaces are maximum for &#952;i = 45°. For near-normal incidence, the probability of sputtering is smaller for the w-GaN phase, suggesting that the atomic arrangement in the pristine state modifies the characteristics of the momentum transfer occurring between the ion and the surface atoms during the collision cascade. Atomic nitrogen sputters preferentially and represents 87% to 100% of sputtered species due to its lower mass. These statistical results differ from the predictions of continuous ion bombardment simulations since the surfaces are not allowed to evolve self-consistently during the gathering of impact statistics. (10.1116/1.3480344)
  DOI : 10.1116/1.3480344
• Dual-frequency capacitive radiofrequency discharges: effect of low-frequency power on electron density and ion flux
  
  • Booth Jean-Paul
  • Curley G.
  • Marić D.
  • Chabert Pascal
  Plasma Sources Science and Technology, IOP Publishing, 2010, 19, pp.015005. The dependence of electron density and ion flux on radiofrequency (RF) power has been measured in a 2 27&#8201;MHz dual-frequency capacitive discharge with silicon electrodes at 6.7&#8201;Pa gas pressure. In Ar/O2 mixtures the electron density and the ion flux vary in a very similar way (i.e. their ratio, &#965;, is constant), in good agreement with the simple electropositive transport theory. Both 27 and 2&#8201;MHz RF powers have a significant effect on the plasma density and the ion flux. The effect of the 2&#8201;MHz power is likely a combination of enhanced plasma heating by dual-frequency excitation and ionization caused by secondary electron beams, which are known to be produced efficiently at oxidized silicon surfaces. In contrast, in Ar/C4F8/O2 mixtures such as those used for industrial dielectric etching, &#965; is always bigger than the theoretical electropositive value, and becomes very high when the ratio of 2 to 27&#8201;MHz power is high. Under these conditions the electron density is very small, whereas the ion flux remains considerable. We attribute the increased plasma transport to the presence of a significant density of F&#8722; negative ions, combined with increased penetration of the 2&#8201;MHz electric field into the plasma bulk at high 2/27&#8201;MHz power ratios. (10.1088/0963-0252/19/1/015005)
  DOI : 10.1088/0963-0252/19/1/015005
• Entropy production rate in tokamaks with nonaxisymmetric magnetic fields
  
  • Garbet X.
  • Abiteboul J.
  • Trier Elisée
  • Gürcan Özgür D.
  • Sarazin Y.
  • Smolyakov A.
  • Allfrey S.
  • Bourdelle C.
  • Fenzi C.
  • Grandgirard Virginie
  • Ghendrih Philippe
  • Hennequin Pascale
  Physics of Plasmas, American Institute of Physics, 2010, 17, pp.072505. A variational principle based on an extremum of entropy production rate is derived for an integrable Hamiltonian system in the presence of two perturbations, which are resonant on neighboring or identical resonant surfaces. This method can be used to calculate the neoclassical transport in a magnetic fusion device with a nonaxisymmetric magnetic field. When applied to a tokamak with ripple, it provides an efficient means to discriminate between various regimes, depending on collisionality and ripple amplitude. This technique provides a means to test simplified collision operators suitable for gyrokinetic codes. It is found that these operators need only satisfy modest requirements in order to recover the correct neoclassical equilibrium, at least in the large aspect ratio limit. Finally, it appears that the toroidal viscous damping rate due to ripple is usually not negligible, thus removing the degeneracy between the radial electric field and the toroidal velocity. (10.1063/1.3454365)
  DOI : 10.1063/1.3454365
• Error analysis of dimensionless scaling experiments with multiple points using linear regression
  
  • Gürcan Özgür D.
  • Vermare Laure
  • Hennequin Pascale
  • Bourdelle C.
  Nuclear Fusion, IOP Publishing, 2010, 50, pp.022003. A general method of error estimation in the case of multiple point dimensionless scaling experiments, using linear regression and standard error propagation, is proposed. The method reduces to the previous result of Cordey (2009 Nucl. Fusion 49 052001) in the case of a two-point scan. On the other hand, if the points follow a linear trend, it explains how the estimated error decreases as more points are added to the scan. Based on the analytical expression that is derived, it is argued that for a low number of points, adding points to the ends of the scanned range, rather than the middle, results in a smaller error estimate. (10.1088/0029-5515/50/2/022003)
  DOI : 10.1088/0029-5515/50/2/022003
• Strike-point splitting induced by external magnetic perturbations: Observations on JET and MAST and associated modelling
  
  • Nardon Eric
  • Cahyna P.
  • Devaux S.
  • Kirk A.
  • Alfier A.
  • Luna Elena de La
  • de Temmerman G.
  • Denner P.
  • Eich T.
  • Gerbaud Thomas
  • Harting D.
  • Jachmich S.
  • Koslowski H. R.
  • Liang Y.
  • Sun Y.
  Journal of Nuclear Materials, Elsevier, 2010, 1, pp.S914 - S917. Heat flux deposition profiles, calculated from infrared imaging, are presented for JET and MAST cases in the presence of external magnetic perturbations. In L-mode, a clear splitting of the strike-point is observed and well reproduced by modelling based on field line tracing with no plasma magnetic response included (vacuum field approximation). In H-mode, in contrast, the splitting is not clearly observed in spite of being expected from vacuum field modelling. As illustrated by modelling results, screening effects could explain the absence of a clear splitting in H-mode. (C) 2010 Elsevier B.V. All rights reserved.Assoc EURATOM IPP CR, Inst Plasma Phys AS CR Vvi, Prague, Czech Republic.Max Planck Inst Plasma Phys, D-85748 Garching, Germany.Culham Sci Ctr, EURATOM CCFE Fus Assoc, Abingdon OX14 3DB, Oxon, England.Assoc Euratom Enea Fus, Consorzio RFX, I-35127 Padua, Italy.Asociac EURATOM CIEMAT, Lab Nacl Fus, Madrid, Spain.FOM Inst Plasma Phys Rijnhuizen, NL-3439 MN Nieuwegein, Netherlands.Ecole Polytech, CNRS, UMR 7648, LPTP, F-91128 Palaiseau, France.Forschungszentrum Julich, Assoc EURATOM FZJ, D-52425 Julich, Germany.TEC, EURATOM Belgian State Assoc, LPP ERM KMS, Brussels, Belgium. (10.1016/j.jnucmat.2010.10.072)
  DOI : 10.1016/j.jnucmat.2010.10.072
• Overview of Emic Triggered Chorus Emissions in Cluster Data
  
  • Grison B.
  • Pickett J. S.
  • Omura Y.
  • Santolik O.
  • Engebretson M. J.
  • Dandouras I. S.
  • Masson A.
  • Decreau P. M.
  • Adrian M. L.
  • Cornilleau Wehrlin N.
  , 2010, 2010, pp.pp. 1542-1550. Electromagnetic ion cyclotron (EMIC) triggered emissions have been recently observed onboard the Cluster spacecraft close to the plasmapause in the equatorial region of the magnetosphere (Pickett et al., 2010). The nonlinear mechanism of the wave amplification is the same as for the well known whistler-mode chorus emissions (Omura et al., 2010). The EMIC triggered emissions appear as risers: electromagnetic structures that have a positive frequency drift with time. They can thus be considered as the EMIC analogue of rising frequency whistler-mode chorus emissions. In addition, they propagate away from the magnetic equator. These EMIC risers are not common in Cluster data. We present an overview of the properties of all the identified cases. Risers can be sorted out in two groups: in the first one the starting frequency of EMIC emissions is close to one half of the local proton gyrofrequency and the risers have a clear left-hand polarization. In the second group the risers have an opposite polarization with a starting frequency close to one half of the He+ gyrofrequency. Most of the cases have been detected close to 22 MLT (magnetic local time). This dependence will be investigated to determine if it is linked to the orbit effects or if there is a physical cause.
• Performance analysis of magnetic flux compression by plasma liner
  
  • Gasilov V. A.
  • d'Yatchenko S. V.
  • Chuvatin Alexandre S.
  • Ol'Khovskaya O. G.
  • Boldarev A. S.
  • Kartasheva E. L.
  • Bagdasarov G. A.
  Mathematical Models and Computer Simulations, 2010, 2 (3), pp.375-387. in english. The paper presents the results of the theoretical and numerical performance analysis of the experimental scheme for amplification of magnetic flux intensity via its compression by plasma liner. 0D estimations and 2D computations results are compared. The simulations were carried out with the use of RMHD code MARPLE (IMM RAS). The scheme performance affected by the Rayleigh-Taylor instability, developed in the case of initially disturbed plasma shell density, is studied. The possible penetration of the compressor shell plasma from the discharge chamber into the load area results in the nonuniformity of magnetic pressure in it. The simulation proves the possibility of elimination of this unwanted effect by proper selection of the experiments parameters. The correlation of the numerical results for this kind of problems using a simplified 0D model and 2D RMHD simulation with the MARPLE code are demonstrated. The prospects of the plasma magnetic flux compression scheme are discussed. Original Russian Text © V.A. Gasilov, S.V. Dyachenko, A.S. Chuvatin, O.G. Olkhovskaya, A.S. Boldarev, E.L. Kartasheva, G.A. Bagdasarov, 2009, published in Matematicheskoe Modelirovanie, 2009, Vol. 21, No. 11, pp. 5773. (10.1134/S2070048210030117)
  DOI : 10.1134/S2070048210030117
• Laboratory modeling of the interaction of electron beams with a magnetoplasma
  
  • Starodubtsev M. V.
  • Krafft C.
  Radiophysics and Quantum Electronics, Springer Verlag, 2010, 53 (7), pp.401-416. We present the results of laboratory experiments in which the mechanisms of interaction of electron beams with whistler waves in a magnetoplasma are studied. Different mechanisms of whistler generation during the injection of a modulated electron beam in the plasma are studied, and the mechanism of conversion of the beam kinetic energy to radiation is demonstrated. The processes of whistler wave generation by the modulated beam at the &#711; Cerenkov and Doppler resonances are analyzed in detail. The excitation of whistler waves by means of a nonresonant mechanism of the transition radiation is studied. (10.1007/s11141-010-9238-4)
  DOI : 10.1007/s11141-010-9238-4
• Identifying the Driver of Pulsating Aurora
  
  • Nishimura Y.
  • Bortnik J.
  • Li W.
  • Thorne R. M.
  • Lyons L.R.
  • Angelopoulos V.
  • Mende S. B.
  • Bonnell J. W.
  • Le Contel Olivier
  • Cully C. M.
  • Ergun R.
  • Auster U.
  Science, American Association for the Advancement of Science (AAAS), 2010, 330 (6000), pp.81-84. Pulsating aurora, a spectacular emission that appears as blinking of the upper atmosphere in the polar regions, is known to be excited by modulated, downward-streaming electrons. Despite its distinctive feature, identifying the driver of the electron precipitation has been a long-standing problem. Using coordinated satellite and ground-based all-sky imager observations from the THEMIS mission, we provide direct evidence that a naturally occurring electromagnetic wave, lower-band chorus, can drive pulsating aurora. Because the waves at a given equatorial location in space correlate with a single pulsating auroral patch in the upper atmosphere, our findings can also be used to constrain magnetic field models with much higher accuracy than has previously been possible. (10.1126/science.1193186)
  DOI : 10.1126/science.1193186
• STAFF Instrument Products Distributed Through the Cluster Active Archive
  
  • Cornilleau-Wehrlin Nicole
  • Mirioni Laurent
  • Robert Patrick
  • Bouzid V.
  • Maksimovic M.
  • de Conchy Y.
  • Harvey Cc
  • Santolík O.
  , 2010, pp.159--168.
• Analysis of equatorial noise using data from the Cluster and Themis missions
  
  • Hrbackova Z.
  • Santolík O.
  • Pickett J. S.
  • Gurnett D. A.
  • Cornilleau-Wehrlin Nicole
  • Le Contel Olivier
  • Krupar Vratislav
  , 2010, 38, pp.4040. We report the results of the analysis of equatorial noise (EN) using data from the Cluster and Themis spacecraft missions. EN is an intense electromagnetic wave emission that propagates close to the geomagnetic equator between the local proton cyclotron and local lower hybrid frequencies. Recent studies have shown that these waves might play a significant role in the acceleration of electrons to relativistic energies in the outer Van Allen radiation belt. The orbit of the Cluster mission has changed over the last two years, providing us with a larger and statistically more meaningful database from which to carry out our study of EN occurrence. We use onboard analyzed data from the STAFF-SA instrument and high-time resolution waveform data from the WBD instrument collected between 2002 and 2009. We present the results obtained by a systematic analysis of the fine spectral structures of the EN emissions observed by WBD. The frequencies of emission peaks have been visually selected from high-resolution spectrograms. We show histograms of the positions of the source regions of EN. The five spacecraft of the Themis mission have search coil magnetometers onboard which measure wave fluctuations in the frequency bandwidth from 0.1 Hz to 4 kHz. We present the results of the fine spectral analysis of these measurements.