Publications

2009

• Simulation of the ignition of a methane-air mixture by a high-voltage nanosecond discharge
  
  • Aleksandrov N.L.
  • Kindysheva S.V.
  • Kukaev E. N.
  • Starikovskaia Svetlana
  • Starikovskii A.Yu.
  Fizika Plazmy / Plasma Physics Reports, MAIK Nauka/Interperiodica, 2009, 35 (10), pp.867-882. The ignition dynamics of a CH4: O2: N2: Ar = 1: 4: 15: 80 mixture by a high-voltage nanosecond discharge is simulated numerically with allowance for experimental data on the dynamics of the discharge current and discharge electric field. The calculated induction time agrees well with experimental data. It is shown that active particles produced in the discharge at a relatively low deposited energy can reduce the induction time by two orders of magnitude. Comparison of simulation results for mixtures with and without nitrogen shows that addition of nitrogen to the mixture leads to a decrease in the average electron energy in the discharge and gives rise to new mechanisms for accumulation of oxygen atoms due to the excitation of nitrogen electronic states and their subsequent quenching in collisions with oxygen molecules. Acceleration of the discharge-initiated ignition is caused by a faster initiation of chain reactions due to the production of active particles, first of all oxygen atoms, in the discharge. (10.1134/S1063780X09100109)
  DOI : 10.1134/S1063780X09100109
• Role of internal plasma sources in planetary magnetospheres
  
  • Moore T. E.
  • Fok M.-C. H.
  • Delcourt Dominique
  , 2009.
• Nonlinear electron acoustic structures generated on the high-potential side of a double layer
  
  • Pottelette Raymond
  • Berthomier Matthieu
  Nonlinear Processes in Geophysics, European Geosciences Union (EGU), 2009, 16, pp.373-380. High-time resolution measurements of the electron distribution function performed in the auroral upward current region reveals a large asymmetry between the low- and high-potential sides of a double-layer. The latter side is characterized by a large enhancement of a locally trapped electron population which corresponds to a significant part (~up to 30%) of the total electron density. As compared to the background hot electron population, this trapped component has a very cold temperature in the direction parallel to the static magnetic field. Accordingly, the differential drift between the trapped and background hot electron populations generates high frequency electron acoustic waves in a direction quasi-parallel to the magnetic field. The density of the trapped electron population can be deduced from the frequency where the electron acoustic spectrum maximizes. In the auroral midcavity region, the electron acoustic waves may be modulated by an additional turbulence generated in the ion acoustic range thanks to the presence of a pre-accelerated ion beam located on the high-potential side of the double layer. Electron holes characterized by bipolar pulses in the electric field are sometimes detected in correlation with these electron acoustic wave packets. (10.5194/npg-16-373-2009)
  DOI : 10.5194/npg-16-373-2009
• Unveiling the nature of phase transitions in the Vlasov limit for a system with longrange interactions
  
  • Firpo Marie-Christine
  , 2009.
• Disk formation during collapse of magnetized protostellar cores
  
  • Hennebelle Patrick
  • Ciardi Andrea
  Astronomy & Astrophysics - A&A, EDP Sciences, 2009, 506, pp.L29-L32. Context: In the context of star and planet formation, understanding the formation of disks is of fundamental importance. Aims: Previous studies found that the magnetic field has a very strong impact on the collapse of a prestellar cloud, by possibly suppressing the formation of a disk even for relatively modest values of the magnetic intensity. Since observations infer that cores have a substantial level of magnetization, this raises the question of how disks form. However, most studies have been restricted to the case in which the initial angle, alpha, between the magnetic field and the rotation axis equals 0°. Here we explore and analyse the influence of non aligned configurations on disk formation. Methods: We perform 3D ideal MHD, AMR numerical simulations for various values of mu, the ratio of the mass-to-flux to the critical mass-to-flux, and various values of alpha. Results: We find that disks form more easily as alpha increases from 0 to 90°. We propose that as the magnetized pseudo-disks become thicker with increasing alpha, the magnetic braking efficiency is lowered. We also find that even small values of alpha (~=10-20°) show significant differences with the aligned case. Conclusions: Within the framework of ideal MHD, and for our choice of initial conditions, centrifugally supported disks cannot form for values of mu smaller than ~=3 when the magnetic field and the rotation axis are perpendicular, and smaller than about ~=5-10 when they are perfectly aligned. (10.1051/0004-6361/200913008)
  DOI : 10.1051/0004-6361/200913008
• Fluid model of an electronegative discharge with magnetized electrons and unmagnetized ions
  
  • Leray Gary
  • Chabert Pascal
  • Lichtenberg A.J.
  • Lieberman M.A.
  Journal of Physics D: Applied Physics, IOP Publishing, 2009, 42, pp.194020. A fluid model is developed to determine the cross-field equilibrium densities and fluxes in a finite-size electronegative discharge with magnetized electrons and unmagnetized positive and negative ions. A two-dimensional rectangular geometry with a uniform axial magnetic field is considered. After averaging over the axial losses, the fluid equations, including ion inertia terms, are integrated numerically along the transverse direction to determine the equilibrium quantities, for the boundary condition of vanishing electron density and flux at a transverse insulating wall. This yields equilibrium solutions with equal flows of positive and negative ions to the transverse wall, and with equal positive ion and electron flows to the axial walls. An analytical model is developed for this case, neglecting ion inertia, and is used to determine the scaling of the discharge equilibrium with discharge parameters and to optimize the ion fluxes. The model and the numerical integrations are in reasonable agreement. (10.1088/0022-3727/42/19/194020)
  DOI : 10.1088/0022-3727/42/19/194020
• Ignition with Low-Temperature Plasma : Kinetic Mechanism and Experimental Verification
  
  • Starikovskaia Svetlana
  • Aleksandrov N.L.
  • Kosarev I.N.
  • Kindysheva S.V.
  • Starikovskii A.Yu.
  High Energy Chemistry, 2009, 43 (3), pp.213-218. The results of experiments and calculations performed at the Laboratory of Physics of Nonequilibrium Systems, Moscow Institute of Physics and Technology from 1996 to 2008 to demonstrate the efficiency of low-temperature plasma in initiation of combustion of gas mixtures over a wide range of initial conditions are surveyed. In the studies reviewed, a method for quantitative analysis of kinetic processes during ignition of combustible gas mixtures by nonequilibrium plasma was developed. (10.1134/S0018143909030096)
  DOI : 10.1134/S0018143909030096
• Validating a quasi-linear transport model versus nonlinear simulations
  
  • Casati A.
  • Bourdelle C.
  • Garbet X.
  • Imbeaux Frédéric
  • Candy J.
  • Clairet F.
  • Dif-Pradalier Guilhem
  • Falchetto G.
  • Gerbaud T.
  • Grandgirard Virginie
  • Gürcan Özgür D.
  • Hennequin Pascale
  • Kinsey J.
  • Ottaviani M.
  • Sabot R.
  • Sarazin Y.
  • Vermare Laure
  • Waltz R. E.
  Nuclear Fusion, IOP Publishing, 2009, 49, pp.085012. In order to gain reliable predictions on turbulent fluxes in tokamak plasmas, physics based transport models are required. Nonlinear gyrokinetic electromagnetic simulations for all species are still too costly in terms of computing time. On the other hand, interestingly, the quasi-linear approximation seems to retain the relevant physics for fairly reproducing both experimental results and nonlinear gyrokinetic simulations. Quasi-linear fluxes are made of two parts: (1) the quasi-linear response of the transported quantities and (2) the saturated fluctuating electrostatic potential. The first one is shown to follow well nonlinear numerical predictions; the second one is based on both nonlinear simulations and turbulence measurements. The resulting quasi-linear fluxes computed by QuaLiKiz (Bourdelle et al 2007 Phys. Plasmas 14 112501) are shown to agree with the nonlinear predictions when varying various dimensionless parameters, such as the temperature gradients, the ion to electron temperature ratio, the dimensionless collisionality, the effective charge and ranging from ion temperature gradient to trapped electron modes turbulence. (10.1088/0029-5515/49/8/085012)
  DOI : 10.1088/0029-5515/49/8/085012
• Nature des transitions de phase hors-équilibre dans un système avec interactions à longue portée
  
  • Firpo Marie-Christine
  , 2009. Papier sélectionné comme communication flash dans la session "Systèmes complexes : la physique statistique a perdu léquilibre . . . ".
• Dynamics and waves near multiple magnetic null points in reconnection diffusion region
  
  • Deng X. H.
  • Zhou M.
  • Li S. Y.
  • Baumjohann W.
  • André M.
  • Cornilleau-Wehrlin Nicole
  • Santolík O.
  • Pontin D. I.
  • Rème H.
  • Lucek E.
  • Fazakerley A.
  • Décréau Pierrette
  • Daly P.
  • Nakamura R.
  • Tang R. X.
  • Hu Y. H.
  • Pang Y.
  • Büchner J.
  • Zhao H.
  • Vaivads A.
  • Pickett J. S.
  • Ng C. S.
  • Lin X.
  • Fu S. Y.
  • Yuan Z. G.
  • Su Z. W.
  • Wang J. F.
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2009, 114 (A7), pp.A07216. Identifying the magnetic structure in the region where the magnetic field lines break and how reconnection happens is crucial to improving our understanding of three-dimensional reconnection. Here we show the in situ observation of magnetic null structures in the diffusion region, the dynamics, and the associated waves. Possible spiral null pair has been identified near the diffusion region. There is a close relation among the null points, the bipolar signature of the Z component of the magnetic field, and enhancement of the flux of energetic electrons up to 100 keV. Near the null structures, whistler-mode waves were identified by both the polarity and the power law of the spectrum of electric and magnetic fields. It is found that the angle between the fans of the nulls is quite close to the theoretically estimated maximum value of the group-velocity cone angle for the whistler wave regime of reconnection. (10.1029/2008JA013197)
  DOI : 10.1029/2008JA013197
• Production of molecules on surface under plasma exposure: Example of NO on pyrex
  
  • Marinov Daniil
  • Guaitella Olivier
  • Rousseau Antoine
  , 2009.
• Landau and non-Landau linear damping: Physics of the dissipation
  
  • Chust Thomas
  • Belmont Gérard
  • Mottez Fabrice
  • Hess S.
  Physics of Plasmas, American Institute of Physics, 2009, 16, pp.2104. For linear Langmuir waves, it is well known that the energy exchanges generally lead to a continuous dissipation, on average, from the electric form to the kinetic one. Many papers have estimated these exchanges and indeed shown that the classical Landau value gamma<SUB>L</SUB>, characterizing the electric field damping, can be derived from this estimation. The paper comes back to this demonstration and its implicit assumption of ``forgetting the initial conditions.'' The limits of the usual energy calculations have become much apparent recently when non-Landau solutions, decreasing with damping rates smaller than gamma<SUB>L</SUB>, have been evidenced [Belmont et al., Phys. Plasmas 15, 052310 (2008)]. Taking advantage of the explicit form provided in this paper for the perturbed distribution function, the dissipation process is revisited here in a more general way. It is shown that the energy calculations, when complete (i.e., when the role of the initial conditions is not excluded by the very hypotheses of the calculations), are indeed in full agreement with the existence of non-Landau solutions; Landau damping, by the way, appears as a particular mode of dissipation, in which the ballistic transport of the initial plasma perturbation leads to negligible effects. Two approaches are presented for this demonstration, Eulerian and Lagrangian, the first one starting from the Vlasov equation and the second from the dynamics of the individual particles. The specific role of the so-called resonant particles is investigated in both formalisms, which provides complementary pictures of the microphysics involved in the energy transfers between field and particles for Landau as well as for non-Landau solutions. (10.1063/1.3205896)
  DOI : 10.1063/1.3205896
• Solar-geomagnetic activity and Aa indices toward a standard classification
  
  • Ouattara Frédéric Martial
  • Amory-Mazaudier Christine
  Journal of Atmospheric and Solar-Terrestrial Physics, Elsevier, 2009, 71, pp.1736-1748. Legrand and Simon [1989. Solar cycle and geomagnetic activity: a review for geophysicists. Part I. The contributions to geomagnetic activity of shock waves and of the solar wind. Annales Geophysicae 7(6), 565-578] classified one century (1868-1978) of geomagnetic activity, using the Mayaud's Aa index, in four classes related to solar activity: (1) the magnetic quiet activity due to slow solar wind flowing around the magnetosphere, (2) the recurrent activity related to high wind speed solar wind, (3) the fluctuating activity related to fluctuating solar wind and (4) the shock activity due to shock events (CME). In this paper, we use this classification to analyse the solar-geomagnetic activity from 1978 to 2005. We found that during the last three decades the level of geomagnetic quiet activity estimated by Aa indices is decreasing: 2003 is the year of the smallest level of quiet geomagnetic activity since 1868. We compare Legrand and Simon's classification with new in situ solar wind data [Richardson, I.G., Cliver, E.W., Cane, H.V., 2000. Sources of geomagnetic activity over the solar cycle: relative importance of coronal mass ejections, high-speed streams, and slow solar wind. Journal of Geophysical research 105(A8), 18,200-18,213; Richardson, I.G., Cane, H.V., 2002. Sources of geomagnetic activity during nearly three solar cycles (1972-2000). Journal of Geophysical Research 107(A8), 1187] and find a rather good agreement. The differences are only due to minor definitions of the extent of the classes. An attempt is made at defining a more precise standard classification of solar phenomena and at defining time scales of these to understand more precisely the geomagnetic signatures of solar activity. (10.1016/j.jastp.2008.05.001)
  DOI : 10.1016/j.jastp.2008.05.001
• Introduction to several papers on special section of 'The Time varying Sun
  
  • Amory-Mazaudier Christine
  • Gregori G.
  • Schroder W.
  Journal of Atmospheric and Solar-Terrestrial Physics, Elsevier, 2009, 17-18, pp.1681-1682. The Sun is at the origin of life on the Earth, and it influences all the Earth's environment, human life, climate, geomagnetism as well as many new technologies systems as for example navigation system. This is why the time varying sun deserves to a trans-disciplinary approach of many topics. In the following 8 papers, we will consider the sun itself its relation with the earth (geomagnetism and climate). (...)
• Absolute Spectral Radiation Measurements From 200-ns 200-kA X-Pinch in 10-eV-10-keV Range With 1-ns Resolution
  
  • Arantchouk Léonid
  • Larour Jean
  IEEE Transactions on Plasma Science, Institute of Electrical and Electronics Engineers, 2009, 37 (4), pp.575-579. A series of seven X-ray diodes and four Si p-i-n detectors with K- and L-filters was employed to measure the absolute time-resolved spectra of 200-ns 200-kA molybdenum and copper X-pinch plasmas. We observe a 10-mum-size 0.4-0.7-ns X-ray source at a total power yield level of 1.5 GW with about 35% in the range above 1 keV. The extreme ultraviolet part of the spectrum can be fitted by a Planckian function with a temperature of 65-75 eV. In the region above 800 eV, the spectrum can be fitted by an exponential distribution with an effective temperature of ~1 keV for Mo X-pinch and ~500 eV for Cu plasma. The X-ray source yields 200-550 mJ in this spectral range. The total XUV and X-ray yield varies in the range 10-30 J. (10.1109/TPS.2009.2013229)
  DOI : 10.1109/TPS.2009.2013229
• Measurements of stray antenna capacitance in the STEREO/WAVES instrument: Comparison of the radio frequency voltage spectrum with models of the galactic nonthermal continuum spectrum
  
  • Eastwood Jonathan P.
  • Bale S. D.
  • Maksimovic M.
  • Zouganelis I.
  • Goetz K.
  • Kaiser M. L.
  • Bougeret J.-L.
  Radio Science, American Geophysical Union, 2009, 44, pp.4012. The STEREO/WAVES instrument is designed to measure interplanetary radio emission and in situ plasma waves in the solar wind. The instrument uses three orthogonal monopole electric antennas as its sensor system in both a pseudodipole and monopole mode. At high radio frequencies, the capacitance of the antennas determines the system gain. Here we estimate the stray capacitance in the antenna system by comparing the measured voltage spectrum with a model of the galactic continuum spectrum, which is the instrument background at high frequencies. Together with the antenna free-space capacitance, these measurements provide an absolute calibration of the STEREO/WAVES experiment at radio frequencies, a prerequisite for quantitative studies of solar and astrophysical radio emission. (10.1029/2009RS004146)
  DOI : 10.1029/2009RS004146
• Foreshock-like density cavity in the outflow region of magnetotail reconnection
  
  • Cai C. L.
  • Dandouras I.
  • Rème H.
  • Cao J.B.
  • Zhou G.C.
  • Parks G. K.
  • Fontaine Dominique
  Annales Geophysicae, European Geosciences Union, 2009, 27, pp.3043-3053. During Cluster spacecraft crossing of the magnetotail, a novel density depleted cavity in association with magnetic compressions in the outflow region of reconnection was observed. It contains intense reflected field-aligned particles, which are produced by a generation mechanism similar to that of the terrestrial foreshock, and hence manifests a foreshock-like morphology. In this cavity, reflected field-aligned proton beams were observed and simultaneously the feature of magnetic-mirror loss-cone proton distributions were found. Magnetic field fluctuations, especially quasi-monochromatic oscillations, were recorded. Both the leading egde and the ULF wave boundary of the ion foreshock are identified from the time sequence of proton and magnetic field observations. Just upstream of the leading egde of the ion foreshock, reflected field-aligned electrons were detected, whose distribution has a narrow bump-on-tail pattern. However, close to the shock front, reflected electrons with a broad bump-on-tail pattern was measured. These two different manifestations of reflected electrons reveal the differences in their microscopic physics of the reflecting process. Moreover, a part of incident ions was further accelerated in the cavity due to trans-time magnetic pumping which provides another possible mechanism in the multi-step acceleration processes in reconnection. (10.5194/angeo-27-3043-2009)
  DOI : 10.5194/angeo-27-3043-2009
• On the electron whistler dispersion law in a cold plasma with light ions and heavy charged particulates
  
  • Lundin B. V.
  • Krafft C.
  Physics of Plasmas, American Institute of Physics, 2009, 16, pp.052104. The dispersion equation of electron whistler waves in a cold plasma with two light ions of comparable gyrofrequencies and heavy charged particulates is derived. It is valid in a very wide frequency range above the highest ion cutoff frequency when the wave frequency is essentially less than the electron plasma frequency. The derived electron whistler dispersion law is expressed through the relative contents of the two light ions and the electrons, as well as the characteristic frequencies of the magnetized plasma, as the lower hybrid resonance frequency, the two highest ion cutoff frequencies, the gyrofrequencies of the light ions, and the electron gyro- and plasma frequencies. The approximation of vanishingly small gyrofrequencies of the heavy ions permits to determine with a relevant accuracy the electron whistler dispersion law using the features of electron whistler spectrograms only. Estimates of the relative charge density of the light ions are obtained and the dispersion laws of the adjacent branches, i.e., the electron whistler waves and the so-called ion cyclotron whistlers are calculated. For the electron whistler waves, the presence of negative ions can be the origin of a manyfold increase in the lower cutoff frequency; a merging effect of the cutoff frequencies of the adjacent branches can also appear. (10.1063/1.3125310)
  DOI : 10.1063/1.3125310
• Acceleration and transport of ions in turbulent current sheets: formation of non-maxwelian energy distribution
  
  • Artemyev A. V.
  • Zelenyi L. M.
  • Malova H. V.
  • Zimbardo G.
  • Delcourt Dominique C.
  Nonlinear Processes in Geophysics, European Geosciences Union (EGU), 2009, 16, pp.631--639. The paper is devoted to particle acceleration in turbulent current sheet (CS). Our results show that the mechanism of CS particle interaction with electromagnetic turbulence can explain the formation of power law energy distributions. We study the ratio between adiabatic acceleration of particles in electric field in the presence of stationary turbulence and acceleration due to electric field in the case of dynamic turbulence. The correlation between average energy gained by particles and average particle residence time in the vicinity of the neutral sheet is discussed. It is also demonstrated that particle velocity distributions formed by particle-turbulence interaction are similar in essence to the ones observed near the far reconnection region in the Earth's magnetotail. (10.5194/npg-16-631-2009)
  DOI : 10.5194/npg-16-631-2009
• Production of molecule on surface under plasma exposure: Example of NO on pyrex
  
  • Marinov Daniil
  • Guaitella Olivier
  • Rousseau Antoine
  , 2009.
• Global model of instabilities in low pressure inductive chlorine discharges
  
  • Despiau-Pujo Emilie
  • Chabert Pascal
  Plasma Sources Science and Technology, IOP Publishing, 2009, 18, pp.045028. Experimental studies have shown that low-pressure inductive discharges with attaching gases are subject to instabilities near the transition between capacitive (E) and inductive (H) modes. A global model, consisting of two particle and one energy balance equations, has been previously proposed to describe the instability mechanism. This model, which agrees qualitatively well with experimental observations, leaves significant quantitative differences. In this paper, the model is revisited with Cl2 as the feedstock gas. A novel treatment of inductive power deposition is evaluated and chlorine chemistry is included. Old and new models are systematically compared. It is found that the alternative inductive coupling description slightly modifies the results. The effect of gas chemistry is even more pronounced. The instability window is smaller in pressure and larger in absorbed power, the frequency is higher and the amplitudes of oscillations are reduced. The feedstock gas is weakly dissociated (≈16%) and Cl2+ is the dominant positive ion, which is consistent with the moderate electron density during the instability cycle. (10.1088/0963-0252/18/4/045028)
  DOI : 10.1088/0963-0252/18/4/045028