Publications

2011

• Impact of collisionality on fluctuation characteristics of micro-turbulence
  
  • Vermare Laure
  • Hennequin Pascale
  • Gürcan Özgür D.
  • Bourdelle C.
  • Clairet F.
  • Garbet X.
  • Sabot R.
  • Tore Supra Team
  Physics of Plasmas, American Institute of Physics, 2011, 18, pp.012306. The influence of changing collisionality on density fluctuation characteristics is studied during dedicated ν∗ scaling experiments, using Doppler backscattering system. First, the repartition of fluctuation energy over different spatial scales, as represented by the wavenumber spectrum, is investigated and a modification of the shape of the perpendicular wavenumber spectrum in the low wavenumber part of the spectrum is observed when changing collisionality. In addition, a new procedure to evaluate the dispersion relation of micro-turbulence is presented. From the behavior of the perpendicular mean velocity of density fluctuations with the perpendicular wavenumber, different dispersion relations are obtained between low and high collisionality cases. (10.1063/1.3536648)
  DOI : 10.1063/1.3536648
• A new 3D parallel multi-species hybrid model for Solar Wind - Mars interaction
  
  • Hess Sebastien
  • Modolo Ronan
  • Mancini Marco
  • Leblanc François
  • Chaufray Jean-Yves
  • Yagi Manabu
  • Allioux R.
  • Richer Emilie
  • Chanteur Gérard
  , 2011, pp.EPSC-DPS2011-770. In the frame of the HELIOSARES project (PI F. Leblanc) dedicated to the modeling of Mars environment (neutral and charged species) from the lower atmosphere to the solar wind, a modeling effort of parallelization has been conducted. Such model allows having a kinetic description of the ions with a rather improved spatial resolution (smaller than the ion inertial less). The latest progresses are reported and simulations results with a uniform spatial resolution of 75 km are presented.
• Different regimes of MHD turbulence with mean magnetic field
  
  • Grappin Roland
  , 2011.
• Anisotropic shell model of turbulence
  
  • Gürcan Özgür D.
  • Grappin Roland
  Physical Review E, American Physical Society (APS), 2011, 84, pp.066308. An anisotropic shell model has been proposed for two-dimensional (2D) turbulence. It is similar to the 2D version of the Gledzer-Ohkitani-Yamada model but with the angular variable in wave-number space divided into three distinct directions representing structures elongated in different directions. In the case when the drive is isotropic the usual isotropic solution is recovered as the fixed point of this model. The Hasegawa-Mima limit of the model is considered in particular due to its relevance for 2D anisotropic systems such a quasigeostrophic and plasma turbulence. It is observed from this simple model that the anisotropy diminishes as a function of scale during the cascade process, and the maximum of the energy is not at the node that has maximum drive, but at a nearby node that is directly coupled to that one. (10.1103/PhysRevE.84.066308)
  DOI : 10.1103/PhysRevE.84.066308
• Observations and modeling of forward and reflected chorus waves captured by THEMIS
  
  • Agapitov O
  • Krasnoselskikh V
  • Zaliznyak Yu
  • Angelopoulos V
  • Le Contel Olivier
  • Rolland G
  Annales Geophysicae, European Geosciences Union, 2011, 29, pp.541-550. Discrete ELF/VLF chorus emissions are the most intense electromagnetic plasma waves observed in the radiation belts of the Earth's magnetosphere. Chorus emissions, whistler-mode wave packets propagating roughly along magnetic field lines from a well-localized source in the vicinity of the magnetic equator to polar regions, can be reflected at low altitudes. After reflection, wave packets can return to the equatorial plane region. Understanding of whistler wave propagation and reflection is critical to a correct description of wave-particle interaction in the radiation belts. We focus on properties of reflected chorus emissions observed by the THEMIS (Time History of Events and Macroscale Interactions During Substorms) spacecraft Search Coil Magnetome-ter (SCM) and Electric Field Instrument (EFI) at ELF/VLF frequencies up to 4 kHz at L ≥ 8. We determine the direction of the Poynting flux and wave vector distribution for forward and reflected chorus waves. Although both types of chorus waves were detected near the magnetic equator and have similar , discrete structure and rising tones, reflected waves are attenuated by a factor of 10–30 and have 10% higher frequency than concurrently-observed forward waves. Model-ing of wave propagation and reflection using geometrical optics ray-tracing allowed us to determine the chorus source region location and explain observed propagation characteristics. We find that reflected wave attenuation at a certain spatial region is caused by divergence of the ray paths of these non-ducted emissions, and that the frequency shift is caused by generation of the reflected waves at lower L-shells where the local equatorial gyrofrequency is larger. (10.5194/angeo-29-541-2011)
  DOI : 10.5194/angeo-29-541-2011
• Role of charge photodesorption in self-synchronized breakdown of surface streamers in air at atmospheric pressure
  
  • Guaitella Olivier
  • Marinov Ilya
  • Rousseau Antoine
  Applied Physics Letters, American Institute of Physics, 2011, 98, pp.071502. A surface dielectric barrier discharge configuration with two identical high voltage electrodes is investigated in air at atmospheric pressure. Synchronized breakdown of streamers on both electrodes is evidenced by statistical study. The light emitted by plasma filament on one electrode can trigger the breakdown of streamers on the other electrode. The role of photodesorption of negative charges deposited on the Pyrex dielectric barrier is responsible for these self-synchronized breakdowns. The binding energy of negative charges photodesorbed is estimated to be lower than 3.5 eV. (10.1063/1.3552965)
  DOI : 10.1063/1.3552965
• NO kinetics in pulsed low-pressure plasmas studied by time-resolved quantum cascade laser absorption spectroscopy
  
  • Welzel S.
  • Guaitella Olivier
  • Lazzaroni Claudia
  • Pintassilgo C.D.
  • Rousseau Antoine
  • Röpcke J.
  Plasma Sources Science and Technology, IOP Publishing, 2011, 20, pp.015020. Time-resolved quantum cascade laser absorption spectroscopy at 1897 cm−1 (5.27 µm) has been applied to study the NO(X) kinetics on the micro- and millisecond time scale in pulsed low-pressure N2/NO dc discharges. Experiments have been performed under flowing and static gas conditions to infer the gas temperature increase and the consequences for the NO line strength. A relatively small increase of ~20 K is observed during the early plasma phase of a few milliseconds. After some 10 ms gas temperatures up to 500 K can be deduced. The experimental data for the NO mixing ratio were compared with the results from a recently developed time-dependent model for pulsed N2O2 plasmas which are well in accord. The early plasma pulse is determined by vibrational heating of N2 while the excitation of NO(X) by N2 metastables is almost completely balanced. Efficient NO depletion occurs after several milliseconds by N atom impact. (10.1088/0963-0252/20/1/015020)
  DOI : 10.1088/0963-0252/20/1/015020