Publications

2009

• Influence of dielectric material on chemistry reactivity in Dielectric Barrier Discharge (DBD)
  
  • Youssef Joseph
  • Bouamra K.
  • Makarov M.
  • Guaitella Olivier
  • Rousseau Antoine
  , 2009.
• Global distribution of whistler-mode chorus waves observed on the THEMIS spacecraft
  
  • Li W.
  • Thorne R. M.
  • Angelopoulos V.
  • Bortnik J.
  • Cully C. M.
  • Ni B.
  • Le Contel Olivier
  • Roux A.
  • Auster U.
  • Magnes W.
  Geophysical Research Letters, American Geophysical Union, 2009, 36, pp.9104. Whistler mode chorus waves are receiving increased scientific attention due to their important roles in both acceleration and loss processes of radiation belt electrons. A new global survey of whistler-mode chorus waves is performed using magnetic field filter bank data from the THEMIS spacecraft with 5 probes in near-equatorial orbits. Our results confirm earlier analyses of the strong dependence of wave amplitudes on geomagnetic activity, confinement of nightside emissions to low magnetic latitudes, and extension of dayside emissions to high latitudes. An important new finding is the strong occurrence rate of chorus on the dayside at L > 7, where moderate dayside chorus is present >10% of the time and can persist even during periods of low geomagnetic activity. (10.1029/2009GL037595)
  DOI : 10.1029/2009GL037595
• Electrostatic solitary waves in current layers: from Cluster observations during a super-substorm to beam experiments at the LAPD
  
  • Pickett J. S.
  • Chen L.-J.
  • Santolík O.
  • Grimald S.
  • Lavraud B.
  • Verkhoglyadova O. P.
  • Tsurutani B. T.
  • Lefebvre B.
  • Fazakerley A.
  • Lakhina G. S.
  • Ghosh S. S.
  • Grison B.
  • Décréau Pierrette
  • Gurnett D. A.
  • Torbert R.
  • Cornilleau-Wehrlin Nicole
  • Dandouras I.
  • Lucek E.
  Nonlinear Processes in Geophysics, European Geosciences Union (EGU), 2009, 16 (3), pp.431-442. Electrostatic Solitary Waves (ESWs) have been observed by several spacecraft in the current layers of Earth's magnetosphere since 1982. ESWs are manifested as isolated pulses (one wave period) in the high time resolution waveform data obtained on these spacecraft. They are thus nonlinear structures generated out of nonlinear instabilities and processes. We report the first observations of ESWs associated with the onset of a super-substorm that occurred on 24 August 2005 while the Cluster spacecraft were located in the magnetotail at around 18-19 R<SUB>E</SUB> and moving northward from the plasma sheet to the lobes. These ESWs were detected in the waveform data of the WBD plasma wave receiver on three of the Cluster spacecraft. The majority of the ESWs were detected about 5 min after the super-substorm onset during which time 1) the PEACE electron instrument detected significant field-aligned electron fluxes from a few 100 eV to 3.5 keV, 2) the EDI instrument detected bursts of field-aligned electron currents, 3) the FGM instrument detected substantial magnetic fluctuations and the presence of Alfvén waves, 4) the STAFF experiment detected broadband electric and magnetic waves, ion cyclotron waves and whistler mode waves, and 5) CIS detected nearly comparable densities of H and O ions and a large tailward H velocity. We compare the characteristics of the ESWs observed during this event to those created in the laboratory at the University of California-Los Angeles Plasma Device (LAPD) with an electron beam. We find that the time durations of both space and LAPD ESWs are only slightly larger than the respective local electron plasma periods, indicating that electron, and not ion, dynamics are responsible for generation of the ESWs. We have discussed possible mechanisms for generating the ESWs in space, including the beam and kinetic Buneman type instabilities and the acoustic instabilities. Future studies will examine these mechanisms in more detail using the space measurements as inputs to models, and better relate the ESW space measurements to the laboratory through PIC code models. (10.5194/npg-16-431-2009)
  DOI : 10.5194/npg-16-431-2009
• Influence of dielectric material in Dielectric Barrier Discharge (DBD) for chemistry reactivity control
  
  • Youssef Joseph
  • Bouamra K.
  • Makarov M.
  • Guaitella Olivier
  • Rousseau Antoine
  , 2009.
• Oblique propagation of whistler mode waves in the chorus source region
  
  • Santolík O.
  • Gurnett D. A.
  • Pickett J. S.
  • Chum J.
  • Cornilleau-Wehrlin Nicole
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2009, 114. Whistler mode chorus has been shown to play a role in the process of local acceleration of electrons in the outer Van Allen radiation belt. Most of the quasi-linear and nonlinear theoretical studies assume that the waves propagate parallel to the terrestrial magnetic field. We show a case where this assumption is invalid. We use data from the Cluster spacecraft to characterize propagation and spectral properties of chorus. The recorded high-resolution waveforms show that chorus in the source region can be formed by a succession of discrete wave packets with decreasing frequency that sometimes change into shapeless hiss. These changes occur at the same time in the entire source region. Multicomponent measurements show that waves in both these regimes can be found at large angles to the terrestrial magnetic field. The hiss intervals contain waves propagating less than one tenth of a degree from the resonance cone. In the regime of discrete wave packets the peak of the wave energy density is found at a few degrees from the resonance cone in a broad interval of azimuth angles. The wave intensity increases with the distance from the magnetic field minimum along a given field line, indicating a gradual amplification of chorus in the source region. (10.1029/2009JA014586)
  DOI : 10.1029/2009JA014586
• Self synchronization of surface discharges in a two electrodes device
  
  • Allegraud Katia
  • Rousseau Antoine
  IEEE Transactions on Dielectrics and Electrical Insulation, Institute of Electrical and Electronics Engineers, 2009, 16 (2), pp.435-439. A twin electrode device coupled to the same high voltage power supply is used to study the propagation of surface streamers. These two identical electrodes are separated from the grounded one by a pyrex plate acting as a dielectric barrier. The gas is dry air, at atmospheric pressure. 1 ns time resolved imaging of the discharge propagation is performed to monitor the discharge ignition and propagation. The discharge consists in filaments which propagate on the dielectric as cathode directed streamers. Each filament transfers 1 nC. The propagation velocities vary from 3.4times107 cm/s at the beginning of the propagation to 7times106 cm/s at the end of the propagation. Ignition at one electrode triggers ignition at the other within 2 ns. (10.1109/TDEI.2009.4815175)
  DOI : 10.1109/TDEI.2009.4815175
• Enhanced confinement with increased extent of the low magnetic shear region in tokamak plasmas
  
  • Nasi L.
  • Firpo Marie-Christine
  Plasma Physics and Controlled Fusion, IOP Publishing, 2009, 51, pp.045006. The Hamiltonian representation of magnetic field lines enables one to study their confinement properties in tokamaks through the use of symplectic maps such as the symmetric tokamap and its bounded version, the latter being introduced here. In this time-independent purely magnetic framework, we observed the drastic improvement in the confinement of magnetic field lines produced by the local vanishing of the shear profile. This amounts to a non-twist condition that notably acts in the same way the safety profile being (non-strictly) monotonic or having a reversed shear. We single out the effect of the amount of flatness of the safety profile in the vicinity of its zero shear point. All other things being equal, the beneficial effect of the vanishing of the shear profile is shown to be increased if the radial extent of the low-shear region is increased. To be specific, the low-shear region induces the formation of a belt of robust KAM tori acting as an internal transport barrier whose width is all the larger as the extent of the low-shear region is broad. (10.1088/0741-3335/51/4/045006)
  DOI : 10.1088/0741-3335/51/4/045006
• Investigation of InP etching mechanisms in a Cl<SUB>2</SUB>/H<SUB>2</SUB> inductively coupled plasma by optical emission spectroscopy
  
  • Gatilova L.
  • Bouchoule S.
  • Guilet S.
  • Chabert Pascal
  Journal of Vacuum Science & Technology A, American Vacuum Society, 2009, 27, pp.262. Optical emission spectroscopy (OES) has been used in order to investigate the InP etching mechanisms in a Cl2H2 inductively coupled plasma. The authors have previously shown that anisotropic etching of InP could be achieved for a H2 percentage in the 35%45% range where the InP etch rate also presents a local maximum [ J. Vac. Sci. Technol. B 24, 2381 (2006) ], and that anisotropic etching was due to an enhanced passivation of the etched sidewalls by a silicon oxide layer [ J. Vac. Sci. Technol. B 26, 666 (2008) ]. In this work, it is shown that this etching behavior is related to a maximum in the H atom concentration in the plasma. The possible enhancement of the sidewall passivation process in the presence of H is investigated by comparing OES measurements and etching results obtained for Cl2H2 and Cl2Ar gas mixtures. (10.1116/1.3071950)
  DOI : 10.1116/1.3071950
• Time-dependent hydrodynamical simulations of slow solar wind, coronal inflows, and polar plumes
  
  • Pinto Rui
  • Grappin Roland
  • Wang Y-M
  • Léorat Jacques
  Astronomy & Astrophysics - A&A, EDP Sciences, 2009, 497 (2), pp.537--543. Aims. We explore the effects of varying the areal expansion rate and coronal heating function on the solar wind flow. Methods. We use a one-dimensional, time-dependent hydrodynamical code. The computational domain extends from near the photosphere, where nonreflecting boundary conditions are applied, to 30 , and includes a transition region where heat conduction and radiative losses dominate. Results. We confirm that the observed inverse relationship between asymptotic wind speed and expansion factor is obtained if the coronal heating rate is a function of the local magnetic field strength. We show that inflows can be generated by suddenly increasing the rate of flux-tube expansion and suggest that this process may be involved in the closing-down of flux at coronal hole boundaries. We also simulate the formation and decay of a polar plume, by including an additional, time-dependent heating source near the base of the flux tube. (10.1051/0004-6361/200811183)
  DOI : 10.1051/0004-6361/200811183
• Physics of non-diffusive turbulent transport of momentum and the origins of spontaneous rotation in tokamaks
  
  • Diamond P.H.
  • Mcdevitt C.J.
  • Gürcan Özgür D.
  • Hahm T.S.
  • Wang W.X.
  • Yoon E.S.
  • Holod I.
  • Lin Z.
  • Naulin V.
  • Singh R.
  Nuclear Fusion, IOP Publishing, 2009, 49, pp.045002. Recent results in the theory of turbulent momentum transport and the origins of intrinsic rotation are summarized. Special attention is focused on aspects of momentum transport critical to intrinsic rotation, namely the residual stress and the edge toroidal flow velocity pinch. Novel results include a systematic decomposition of the physical processes which drive intrinsic rotation, a calculation of the critical external torque necessary to hold the plasma stationary against the intrinsic residual stress, a simple model of net velocity scaling which recovers the salient features of the experimental trends and the elucidation of the impact of the particle flux on the net toroidal velocity pinch. Specific suggestions for future experiments are offered. (10.1088/0029-5515/49/4/045002)
  DOI : 10.1088/0029-5515/49/4/045002
• Wave-Number Spectrum of Drift-Wave Turbulence
  
  • Gürcan Özgür D.
  • Garbet X.
  • Hennequin Pascale
  • Diamond P.H.
  • Casati A.
  • Falchetto G. L.
  Physical Review Letters, American Physical Society, 2009, 102, pp.255002. A simple model for the evolution of turbulence fluctuation spectra, which includes neighboring interactions leading to the usual dual cascade as well as disparate scale interactions corresponding to refraction by large scale structures, is derived. The model recovers the usual Kraichnan-Kolmogorov picture in the case of exclusively local interactions and midrange drive. On the other hand, when disparate scale interactions are dominant, a simple spectrum for the density fluctuations of the form |nk|2&#8733;k&#8722;3/(1 k2)2 is obtained. This simple prediction is then compared to, and found to be in fair agreement with, Tore Supra CO2 laser scattering data. (10.1103/PhysRevLett.102.255002)
  DOI : 10.1103/PhysRevLett.102.255002
• Long range correlation studies : Tore Supra contribution, DREVE project
  
  • Vermare Laure
  • Hennequin Pascale
  • Gürcan Özgür D.
  • Honoré Cyrille
  • Sabot R.
  • Giacalone J-C.
  • Tore Supra Team
  , 2009.
• Evidence of a Cascade and Dissipation of Solar-Wind Turbulence at the Electron Gyroscale
  
  • Sahraoui Fouad
  • Goldstein M. L.
  • Robert Patrick
  • Khotyaintsev Y. V.
  Physical Review Letters, American Physical Society, 2009, 102 (23), pp.231102. We report the first direct determination of the dissipation range of magnetofluid turbulence in the solar wind at the electron scales. Combining high resolution magnetic and electric field data of the Cluster spacecraft, we computed the spectrum of turbulence and found two distinct breakpoints in the magnetic spectrum at 0.4 and 35 Hz, which correspond, respectively, to the Doppler-shifted proton and electron gyroscales, f&#961;p and f&#961;e. Below f&#961;p, the spectrum follows a Kolmogorov scaling f&#8722;1.62, typical of spectra observed at 1 AU. Above f&#961;p, a second inertial range is formed with a scaling f&#8722;2.3 down to f&#961;e. Above f&#961;e, the spectrum has a steeper power law &#8764;f&#8722;4.1 down to the noise level of the instrument. We interpret this as the dissipation range and show a remarkable agreement with theoretical predictions of a quasi-two-dimensional cascade into Kinetic Alfvén Waves (KAW). (10.1103/PhysRevLett.102.231102)
  DOI : 10.1103/PhysRevLett.102.231102
• Whistler wave radiation from a loop antenna located in a cylindrical density depletion
  
  • Kudrin A. V.
  • Bakharev P. V.
  • Krafft C.
  • Zaboronkova T. M.
  Physics of Plasmas, American Institute of Physics, 2009, 16, pp.063502. Electromagnetic radiation from sources in a magnetoplasma containing a radially nonuniform cylindrical density depletion is considered. Using a rigorous solution for the total field comprising both the discrete and continuous parts of the spatial spectrum of excited waves, the radiation resistance of a loop antenna and the efficiency of excitation of different modes by such a source are determined in the whistler range. Based on the numerical results, conditions are revealed under which the power radiated from a loop antenna located in a density depletion is dominated by the contribution of either discrete- or continuous-spectrum modes. It is found that the radiation resistance of the loop antenna in a weakly nonuniform density depletion can be notably greater than that in a homogeneous magnetoplasma whose parameters coincide with those near the depletion axis. The results are relevant to the basic properties of whistler wave excitation in the presence of field-aligned plasma density irregularities and can be useful for wave diagnostics in laboratory and space plasmas. (10.1063/1.3142469)
  DOI : 10.1063/1.3142469
• Auroral evidence for multiple reconnection in the magnetospheric tail plasma sheet
  
  • Treumann R. A.
  • Jaroschek C. H.
  • Pottelette Raymond
  EPL - Europhysics Letters, European Physical Society / EDP Sciences / Società Italiana di Fisica / IOP Publishing, 2009, 85, pp.49001. We present auroral evidence for multiple and, most probably, small-scale reconnection in the near-Earth magnetospheric plasma sheet current layer during auroral activity. Hall currents as the source of upward and downward field-aligned currents require the generation of the corresponding electron fluxes. The auroral spatial ordering in a multiple sequence of these fluxes requires the assumption of the existence of several ―-and possibly―- even many tailward reconnection sites. (10.1209/0295-5075/85/49001)
  DOI : 10.1209/0295-5075/85/49001
• Observations of Double Layers in Earth's Plasma Sheet
  
  • Ergun R. E.
  • Andersson L.
  • Tao J. B.
  • Angelopoulos V.
  • Bonnell J. W.
  • Mcfadden J. P.
  • Larson D. E.
  • Eriksson S.
  • Johansson T.
  • Cully C. M.
  • Newman D. N.
  • Goldman M. V.
  • Roux A.
  • Le Contel Olivier
  • Glassmeier K.-H.
  • Baumjohann W.
  Physical Review Letters, American Physical Society, 2009, 102, pp.155002. We report the first direct observations of parallel electric fields (E<SUB>||</SUB>) carried by double layers (DLs) in the plasma sheet of Earth's magnetosphere. The DL observations, made by the THEMIS spacecraft, have E<SUB>||</SUB> signals that are analogous to those reported in the auroral region. DLs are observed during bursty bulk flow events, in the current sheet, and in plasma sheet boundary layer, all during periods of strong magnetic fluctuations. These observations imply that DLs are a universal process and that strongly nonlinear and kinetic behavior is intrinsic to Earth's plasma sheet. (10.1103/PhysRevLett.102.155002)
  DOI : 10.1103/PhysRevLett.102.155002
• NO production on pyrex under, and after plasma exposure
  
  • Marinov Daniil
  • Guaitella Olivier
  • Rousseau Antoine
  , 2009.
• Mechanisms of filamentary plasma/catalyst coupling for air treatment
  
  • Guaitella Olivier
  • Rousseau Antoine
  • Allegraud Katia
  • Celestin S.
  , 2009.
• Kinetics of ignition of saturated hydrocarbons by nonequilibrium plasma : C<SUB>2</SUB>H<SUB>6</SUB>- to C<SUB>5</SUB>H<SUB>12</SUB>-containing mixtures
  
  • Kosarev I.N.
  • Aleksandrov N.L.
  • Kindysheva S.V.
  • Starikovskaia Svetlana
  • Starikovskii A.Yu.
  Combustion and Flame, Elsevier, 2009, 156 (1), pp.221-233. The kinetics of ignition in CnH2n 2:O2:Ar mixtures for n = 2 to 5 has been studied experimentally and numerically after a high-voltage nanosecond discharge. The ignition delay time behind a reflected shock wave was measured with and without the discharge. It was shown that the initiation of the discharge with a specific deposited energy of 1030 mJ/cm3 leads to an order of magnitude decrease in the ignition delay time. Discharge processes and following chain chemical reactions with energy release were simulated. The generation of atoms, radicals and excited and charged particles was numerically simulated using the measured time-resolved discharge current and electric field in the discharge phase. The calculated densities of the active particles were used as input data to simulate plasma-assisted ignition. The sensitivity of the results to variation in electron cross sections, reaction rates and radical composition was investigated. Good agreement was obtained between the calculated ignition delay times and the experimental data. The analysis of the simulation results showed that the effect of nonequilibrium plasma on the ignition delay is associated with faster development of chain reactions, due to atoms and radicals produced by the electron impact dissociation of molecules in the discharge phase. Finally, we studied the role of various hydrocarbon radicals in the plasma-assisted ignition of the mixtures under consideration. (10.1016/j.combustflame.2008.07.013)
  DOI : 10.1016/j.combustflame.2008.07.013
• Edge-to-center plasma density ratio in high density plasma sources
  
  • Raimbault Jean-Luc
  • Chabert Pascal
  Plasma Sources Science and Technology, IOP Publishing, 2009, 18, pp.014017. The flux of positive ions leaving a classical low-temperature plasma discharge is proportional to the plasma density at the plasmasheath edge, and the edge-to-center plasma density ratio, the so-called hl factor, normally depends only on the discharge size and the neutral gas pressure. The ion flux leaving the discharge is therefore linearly proportional to the central plasma density. The hl factor has been previously derived by solving the plasma transport equations over a large pressure range, with the assumption of constant neutral gas density within the discharge. Tonks and Langmuir derived the low pressure (collisionless) solution of this problem in 1929. More recent works have shown that the neutral gas density is no longer constant when the plasma pressure becomes comparable to the neutral gas pressure. In this paper, we solve the plasma transport equations in this new situation and we propose a new expression for the hl factor. It is shown that hl becomes a function of the central plasma density which implies that the ion flux leaving the discharge is no longer proportional to this density. This effect has to be included in particle and energy balance equations used in global models of high density plasma sources. (10.1088/0963-0252/18/1/014017)
  DOI : 10.1088/0963-0252/18/1/014017
• Study of hydrogen plasma in the negative-ion extraction region
  
  • Svarnas P.
  • Annaratone B.M.
  • Béchu Stéphane
  • Pelletier J.
  • Bacal M.
  Plasma Sources Science and Technology, IOP Publishing, 2009, 18, pp.045010. (10.1088/0963-0252/18/4/045010)
  DOI : 10.1088/0963-0252/18/4/045010
• Capture of solar wind alpha-particles by the Martian atmosphere
  
  • Chanteur Gérard
  • Dubinin E.
  • Modolo Ronan
  • Fraenz M.
  Geophysical Research Letters, American Geophysical Union, 2009, 36 (23), pp.L23105. Integration along He++ test-particle trajectories in the self-consistent electromagnetic fields generated by three-dimensional hybrid simulations of the solar wind/Mars interaction is used to evaluate the removal of solar wind α-particles due to charge-exchange processes with neutral species of the Martian exosphere. The total removal rate of solar wind He++ ions, transformed into either singly ionised or neutral helium, is equal to 6.7 × 1023 s−1, which corresponds approximately to 30% of the flux of solar α-particles through the planetary cross-section. The deposition rate of helium neutral atoms, created by double electronic capture on exospheric oxygen, impacting the exobase, and penetrating below where it can be trapped, is about 1.5 × 1023 s−1. That means an important contribution of the solar wind source to the helium balance of the Martian atmosphere. The implantation of the solar helium into the Martian atmosphere shows an asymmetry related to the orientation of the motional electric field of the solar wind, −VSW × BIMF. (10.1029/2009GL040235)
  DOI : 10.1029/2009GL040235
• What can we learn from HF signal scattered from a discrete arc?
  
  • Seran Elena
  • Godefroy Michel
  • Kauristie K.
  • Cerisier Jean-Claude
  • Berthelier Jean-Jacques
  • Lester M.
  • Sarri L.-E.
  Annales Geophysicae, European Geosciences Union, 2009, 27 (5), pp.1887-1896. We present observations of a discrete southward propagating arc which appeared in the mid-night sector at latitudes equatorward of main substorm activity. The arc observations were made simultaneously by the ALFA (Auroral Light Fine Analysis) optical camera, the SuperDARN-CUTLASS HF radar and the Demeter satellite during a coordinated multi-instrumental campaign conducted at the KEOPS/ESRANGE site in December 2006. The SuperDARN HF signal which is often lost in the regions of strong electron precipitation yields in our case clear backscatter from an isolated arc of weak intensity. Consequently we are able to study arc dynamics, the formation of meso-scale irregularities of the electron density along the arc, compare the arc motion with the convection of surrounding plasma and discuss the contribution of ionospheric ions in the arc erosion and its propagation. (10.5194/angeo-27-1887-2009)
  DOI : 10.5194/angeo-27-1887-2009
• Time resolved quantum cascade laser absorption spectroscopy on NO containing pulsed DC discharges
  
  • Welzel S.
  • Guaitella Olivier
  • Pintassilgo C.D.
  • Rousseau Antoine
  • Roepcke J.
  , 2009.
• Dust Detection by the Wave Instrument on STEREO: Nanoparticles Picked up by the Solar Wind?
  
  • Meyer-Vernet N.
  • Maksimovic M.
  • Czechowski A.
  • Mann I. R.
  • Zouganelis I.
  • Goetz K.
  • Kaiser M. L.
  • St. Cyr O. C.
  • Bougeret J.-L.
  • Bale S. D.
  Solar Physics, Springer Verlag, 2009, 256 (1-2), pp.463-474. The STEREO wave instrument (S/WAVES) has detected a very large number of intense voltage pulses. We suggest that these events are produced by impact ionisation of nanoparticles striking the spacecraft at a velocity of the order of magnitude of the solar wind speed. Nanoparticles, which are half-way between micron-sized dust and atomic ions, have such a large charge-to-mass ratio that the electric field induced by the solar wind magnetic field accelerates them very efficiently. Since the voltage produced by dust impacts increases very fast with speed, such nanoparticles produce signals as high as do much larger grains of smaller speeds. The flux of 10-nm radius grains inferred in this way is compatible with the interplanetary dust flux model. The present results may represent the first detection of fast nanoparticles in interplanetary space near Earth orbit. (10.1007/s11207-009-9349-2)
  DOI : 10.1007/s11207-009-9349-2