Publications

2009

• Plasma sheet circulation pathways
  
  • Moore T. E.
  • Fok M.-C. H.
  • Delcourt Dominique
  • Slinker Steve P.
  • Damiano P.
  , 2009.
• Titan's ionosphere in the magnetosheath : Cassini RPWS results during the T32 flyby
  
  • Garnier P.
  • Wahlund J.-E.
  • Rosenqvist L.
  • Modolo Ronan
  • Agren K.
  • Sergis N.
  • Canu Patrick
  • Andre M.
  • Gurnett D.A.
  • Kurth W.S.
  • Krimigis S.M.
  • Coates A.
  • Dougherty M.
  • Waite J.H
  Annales Geophysicae, European Geosciences Union, 2009, 27 (11), pp.4257-4272. The Cassini mission has provided much information about the Titan environment, with numerous low altitude encounters with the moon being always inside the magnetosphere. The only encounter taking place outside the magnetopause, in the magnetosheath, occurred the 13 June 2007 (T32 flyby). This paper is dedicated to the analysis of the Radio and Plasma Wave investigation data during this specific encounter, in particular with the Langmuir probe, providing a detailed picture of the cold plasma environment and of Titan's ionosphere with these unique plasma conditions. The various pressure terms were also calculated during the flyby. The comparison with the T30 flyby, whose geometry was very similar to the T32 encounter but where Titan was immersed in the kronian magnetosphere, reveals that the evolution of the incident plasma has a significant influence on the structure of the ionosphere, with in particular a change of the exo-ionospheric shape. The electrical conductivities are given along the trajectory of the spacecraft and the discovery of a polar plasma cavity is reported. (10.5194/angeo-27-4257-2009)
  DOI : 10.5194/angeo-27-4257-2009
• Shape, size, velocity and field-aligned currents of dayside plasma injections: a multi-altitude study
  
  • Marchaudon Aurelie
  • Cerisier Jean-Claude
  • Dunlop M.W.
  • Pitout Frederic
  • Bosqued Jean-Michel
  • Fazakerley A. N.
  Annales Geophysicae, European Geosciences Union, 2009, 27 (3), pp.1251-1266. On 20 February 2005, Cluster in the outer magnetosphere and Double Star-2 (TC-2) at mid-altitude are situated in the vicinity of the northern cusp/mantle, with Cluster moving sunward and TC-2 anti-sunward. Their magnetic footprints come very close together at about 15:28 UT, over the common field-of-view of SuperDARN radars. Thanks to this conjunction, we determine the velocity, the transverse sizes, perpendicular and parallel to this velocity, and the shape of three magnetic flux tubes of magnetosheath plasma injection. The velocity of the structures determined from the Cluster four-spacecraft timing analysis is almost purely antisunward, in contrast with the antisunward and duskward convection velocity inside the flux tubes. The transverse sizes are defined from the Cluster-TC-2 separation perpendicular to the magnetic field, and from the time spent by a Cluster spacecraft in one structure; they are comprised between 0.6 and 2 RE in agreement with previous studies. Finally, using a comparison between the eigenvectors deduced from a variance analysis of the magnetic perturbation at the four Cluster and at TC-2, we show that the upstream side of the injection flux tubes is magnetically well defined, with even a concave front for the third one giving a bean-like shape, whereas the downstream side is far more turbulent. We also realise the first quantitative comparison between field-aligned currents at Cluster calculated with the curlometer technique and with the single-spacecraft method, assuming infinite parallel current sheets and taking into account the velocity of the injection flux tubes. The results agree nicely, confirming the validity of both methods. Finally, we compare the field-aligned current distribution of the three injection flux tubes at the altitudes of Cluster and TC-2. Both profiles are fairly similar, with mainly a pair of opposite field-aligned currents, upward at low-latitude and downward at high-latitude. In terms of intensity, the field-aligned currents at Cluster are two to three times less intense than at TC-2 for the first two flux tubes, in agreement with magnetic field line convergence. For the third flux tube, the intensity is equal, which is explained by the fact that TC-2 crosses the tube on its edge. Finally, the analysis of the ion and electron moments at Cluster shows that the field-aligned currents result from a small difference between upward ion and electron fluxes. (10.5194/angeo-27-1251-2009)
  DOI : 10.5194/angeo-27-1251-2009
• 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
• A review of new wire arrays with open and closed magnetic configurations at the 1.6 MA Zebra generator for radiative properties and opacity effects
  
  • Kantsyrev Viktor L.
  • Safronova Alla S.
  • Esaulov A. A.
  • Williamson Kenneth M.
  • Shrestha Ishor
  • Yilmaz M. F.
  • Osborne Glenn C.
  • Weller Michael E.
  • Ouart N. D.
  • Shlyaptseva V. V.
  • Rudakov Leonid I.
  • Chuvatin Alexandre S.
  • Velikovich A. L.
  High Energy Density Physics, Elsevier, 2009, 5 (3), pp.115-123. Review The studies emphasize investigation of plasma formation, implosion, and radiation features as a function of two load configurations: compact multi-planar and cylindrical wire arrays. Experiments with different Z-pinch loads were performed on 1.6 MA, 100 ns, Zebra generator at University of Nevada, Reno. The multi-planar wire arrays (PWAs) were studied in open and closed configurations with Al, Cu, brass, Mo and W wires. In the open magnetic configurations (single, double, triple PWAs) magnetic fields are present inside the arrays from the beginning of discharge, while in closed configurations (prism-like PWA) the global magnetic field is excluded inside before plasma flow occurs. The new prism-like PWA allows high flexibility in control of implosion dynamics and precursor formation. The spectral modeling, magneto-hydrodynamic (MHD) and wire ablation dynamic model (WADM) codes were used to describe the plasma evolution and plasma parameters. Experimentally observed electron temperature and density in multiple bright spots reached 1.4 keV and 5 × 10E21 cm−3, respectively. Two types of bright spots were observed. With peak currents up to 1.3 MA opacity effects became more pronounced and led to a limiting of the X-ray yields from compact cylindrical arrays. Despite different magnetic energy to plasma coupling mechanisms early in the implosion a comparison of compact double PWA and cylindrical WA results indicates that during the stagnation stage the same plasma heating mechanism may occur. The double PWA was found to be the best radiator tested at University scale 1 MA generator. It is characterized by a combination of larger yield and power, mm-scale size, and provides the possibility of radiation pulse shaping. Further, the newer configuration, the double PWA with skewed wires, was tested and showed the possibility of a more effective X-ray generation. (10.1016/j.hedp.2009.04.001)
  DOI : 10.1016/j.hedp.2009.04.001
• Unveiling the nature of out-of-equilibrium phase transitions in a system with long-range interactions
  
  • Firpo Marie-Christine
  EPL - Europhysics Letters, European Physical Society / EDP Sciences / Società Italiana di Fisica / IOP Publishing, 2009, 88, pp.30010. Recently, there has been some vigorous interest in the out-of-equilibrium quasistationary states (QSSs), with lifetimes diverging with the number N of degrees of freedom, emerging from numerical simulations of the ferromagnetic XY Hamiltonian Mean Field (HMF) starting from some special initial conditions. Phase transitions have been reported between low-energy magnetized QSSs and large-energy unexpected, antiferromagnetic-like, QSSs with low magnetization. This issue is addressed here in the Vlasov N→∞ limit. It is argued that the time-asymptotic states emerging in the Vlasov limit can be related to simple generic time-asymptotic forms for the force field. The proposed picture unveils the nature of the out-of-equilibrium phase transitions reported for the ferromagnetic HMF: this is a bifurcation point connecting an effective integrable Vlasov one-particle time-asymptotic dynamics to a partly ergodic one which means a brutal open-up of the Vlasov one-particle phase space. Illustration is given by investigating the time-asymptotic value of the magnetization at the phase transition, under the assumption of a sufficiently rapid time-asymptotic decay of the transient force field. (10.1209/0295-5075/88/30010)
  DOI : 10.1209/0295-5075/88/30010
• FLUCTUATION MEASUREMENTS AND THEIR LINK WITH TRANSPORT ON TORE SUPRA
  
  • Sabot R.
  • Hennequin Pascale
  • Colas L.
  Fusion Science and Technology, Taylor & Francis, 2009, 56 (3), pp.1253-1272. Measurement of turbulence properties provides key insight to understand anomalous transport in magnetic fusion devices. On Tore Supra, scattering diagnostics and reflectometers have been used to measure density fluctuations in the plasma core. A cross-polarization scattering diagnostic was also the first diagnostic to measure the turbulence magnetic fluctuations in a fusion plasma core. This paper presents the principle and the experimental setup of these diagnostics, with chosen results illustrating their capabilities to determine the spatial structure of the turbulence and to assess the link between energy transport and fluctuations. These flexible and complementary measurements made it possible to analyze the confinement and fluctuation scaling laws with non-dimensional parameters, which requires a wide variety of plasma conditions.
• Kelvin-Helmholtz waves at the Earth's magnetopause: Multiscale development and associated reconnection
  
  • Hasegawa H.
  • Retinò Alessandro
  • Vaivads A.
  • Khotyaintsev Y. V.
  • André M.
  • Nakamura T. K. M.
  • Teh W.-L.
  • Sonnerup B. U. Ö.
  • Schwartz S. J.
  • Seki Y.
  • Fujimoto M.
  • Saito Y.
  • Rème H.
  • Canu Patrick
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2009, 114, pp.12207. We examine traversals on 20 November 2001 of the equatorial magnetopause boundary layer simultaneously at 1500 magnetic local time (MLT) by the Geotail spacecraft and at 1900 MLT by the Cluster spacecraft, which detected rolled-up MHD-scale vortices generated by the Kelvin-Helmholtz instability (KHI) under prolonged northward interplanetary magnetic field conditions. Our purpose is to address the excitation process of the KHI, MHD-scale and ion-scale structures of the vortices, and the formation mechanism of the low-latitude boundary layer (LLBL). The observed KH wavelength (>4 × 10<SUP>4</SUP> km) is considerably longer than predicted by the linear theory from the thickness (1000 km) of the dayside velocity shear layer. Our analyses suggest that the KHI excitation is facilitated by combined effects of the formation of the LLBL presumably through high-latitude magnetopause reconnection and compressional magnetosheath fluctuations on the dayside, and that breakup and/or coalescence of the vortices are beginning around 1900 MLT. Current layers of thickness a few times ion inertia length 100 km and of magnetic shear 60° existed at the trailing edges of the vortices. Identified in one such current sheet were signatures of local reconnection: Alfvénic outflow jet within a bifurcated current sheet, nonzero magnetic field component normal to the sheet, and field-aligned beam of accelerated electrons. Because of its incipient nature, however, this reconnection process is unlikely to lead to the observed dusk-flank LLBL. It is thus inferred that the flank LLBL resulted from other mechanisms, namely, diffusion and/or remote reconnection unidentified by Cluster. (10.1029/2009JA014042)
  DOI : 10.1029/2009JA014042
• Turbulence in the TORE SUPRA Tokamak: Measurements and Validation of Nonlinear Simulations
  
  • Casati A.
  • Gerbaud T.
  • Hennequin P.
  • Heuraux Stéphane
  Physical Review Letters, American Physical Society, 2009, 102, pp.165005. Turbulence measurements in TORE SUPRA tokamak plasmas have been quantitatively compared to predictions by nonlinear gyrokinetic simulations. For the first time, numerical results simultaneously match within experimental uncertainty (a) the magnitude of effective heat diffusivity, (b) rms values of density fluctuations, and (c) wave-number spectra in both the directions perpendicular to the magnetic field. Moreover, the nonlinear simulations help to revise as an instrumental effect the apparent experimental evidence of strong turbulence anisotropy at spatial scales of the order of ion-sound Larmor radius.
• 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
• 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
• 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.
• International Heliophysical Year: GPS Network in Africa
  
  • Amory-Mazaudier Christine
  • Basu S.
  • Bock Olivier
  • Combrink A.
  • Groves K.
  • Fuller Rowell T.
  • Lassudrie-Duchesne Patrick
  • Petitdidier Monique
  • Yizengaw E.
  Earth, Moon, and Planets, Springer Verlag, 2009, 104 (1-4), pp.263-270. The main scientific objectives of the International Heliophysical Year are to discover and study all the physical processes coupling the Earth to the Sun. During the IHY a number of scientific instruments are being deployed all over the world. This brief report presents the scientific objectives, the GPS receiver network over Africa and the long lasting research planned for the next decades in Africa (10.1007/s11038-008-9273-8)
  DOI : 10.1007/s11038-008-9273-8
• A comment on the paper 'Solar activity and its influence on climate' Author C. de Jager Published in Netherlands Journal of Geosciences-Geologie en Mijnbouw, 87-3, pp 207213, 3 2008
  
  • Amory-Mazaudier Christine
  • Legrand J.P.
  NETHERLANDS JOURNAL OF GEOSCIENCES-GEOLOGIE EN MIJNBOUW, 2009, [88-3] 177, pp.[88-3] 177. The purpose of this comment is not to criticize the results obtained by Dr C. de Jager, and we agree for example with his prediction of the next sunspot cycle amplitude - 68 with σ= 17.
• Dispersion relations of electron density fluctuations in a Hall thruster plasma, observed by collective light scattering
  
  • Tsikata Sedina
  • Lemoine N.
  • Pisarev V.
  • Grésillon D.
  Physics of Plasmas, American Institute of Physics, 2009, 16, pp.033506. Kinetic models and numerical simulations of E×B plasma discharges predict microfluctuations at the scales of the electron cyclotron drift radius and the ion plasma frequency. With the help of a specially designed collective scattering device, the first experimental observations of small-scale electron density fluctuations inside the plasma volume are obtained, and observed in the expected ranges of spatial and time scales. The anisotropy, dispersion relations, form factor, amplitude, and spatial distribution of these electron density fluctuations are described and compared to theoretical expectations. (10.1063/1.3093261)
  DOI : 10.1063/1.3093261
• Toroidal Rotation Driven by the Polarization Drift
  
  • Mcdevitt C.J.
  • Diamond P.H.
  • Gürcan Özgür D.
  • Hahm T.S.
  Physical Review Letters, American Physical Society, 2009, 103, pp.205003. Starting from a phase space conserving gyrokinetic formulation, a systematic derivation of parallel momentum conservation uncovers a novel mechanism by which microturbulence may drive intrinsic rotation. This mechanism, which appears in the gyrokinetic formulation through the parallel nonlinearity, emerges due to charge separation induced by the polarization drift. The derivation and physical discussion of this mechanism will be pursued throughout this Letter. (10.1103/PhysRevLett.103.205003)
  DOI : 10.1103/PhysRevLett.103.205003
• Quasi-parallel whistler mode waves observed by THEMIS during near-earth dipolarizations
  
  • Le Contel Olivier
  • Roux A.
  • Jacquey C.
  • Robert Patrick
  • Berthomier Matthieu
  • Chust Thomas
  • Grison B.
  • Angelopoulos V.
  • Sibeck David G.
  • Chaston C. C.
  • Cully C. M.
  • Ergun B.
  • Glassmeier K.-H.
  • Auster U.
  • Mcfadden J. P.
  • Carlson C. W.
  • Larson D. E.
  • Bonnell J. W.
  • Mende S. B.
  • Russell C. T.
  • Donovan E.
  • Mann I. R.
  • Singer H.
  Annales Geophysicae, European Geosciences Union, 2009, 27, pp.2259-2275. We report on quasi-parallel whistler emissions detected by the near-earth satellites of the THEMIS mission before, during, and after local dipolarization. These emissions are associated with an electron temperature anisotropy alpha=T<SUB>&#8869;e</SUB>/T<SUB>||e</SUB>>1 consistent with the linear theory of whistler mode anisotropy instability. When the whistler mode emissions are observed the measured electron anisotropy varies inversely with beta<SUB>||e</SUB> (the ratio of the electron parallel pressure to the magnetic pressure) as predicted by Gary and Wang (1996). Narrow band whistler emissions correspond to the small alpha existing before dipolarization whereas the broad band emissions correspond to large alpha observed during and after dipolarization. The energy in the whistler mode is leaving the current sheet and is propagating along the background magnetic field, towards the Earth. A simple time-independent description based on the Liouville's theorem indicates that the electron temperature anisotropy decreases with the distance along the magnetic field from the equator. Once this variation of alpha is taken into account, the linear theory predicts an equatorial origin for the whistler mode. The linear theory is also consistent with the observed bandwidth of wave emissions. Yet, the anisotropy required to be fully consistent with the observations is somewhat larger than the measured one. Although the discrepancy remains within the instrumental error bars, this could be due to time-dependent effects which have been neglected. The possible role of the whistler waves in the substorm process is discussed. (10.5194/angeo-27-2259-2009)
  DOI : 10.5194/angeo-27-2259-2009
• Slow Solar Wind From Open Regions with Strong Low-Coronal Heating
  
  • Wang Y-M
  • Ko Y-K
  • Grappin Roland
  The Astrophysical Journal, American Astronomical Society, 2009, 691 (1), pp.760--769. By comparing solar wind data taken by the Advanced Composition Explorer during 1998-2007 with extrapolations of the observed photospheric magnetic field, we verify that high O7 /O6 and Fe/O ratios are associated with low wind speeds, large expansion factors, strong footpoint fields, and high mass and energy flux densities at the coronal base. As demonstrated by model calculations, these correlations are consistent with the idea that the bulk of the slow wind originates from regions of rapidly diverging open flux, where the coronal heating is concentrated at low heights. We identify two main components of the slow wind, one emanating from small coronal holes near active regions and characterized by particularly strong low-coronal heating, the other coming from just inside the polar-hole boundaries and characterized by weaker low-coronal heating and intermediate O7 /O6 and Fe/O ratios. (10.1088/0004-637X/691/1/760)
  DOI : 10.1088/0004-637X/691/1/760
• Role of internal plasma sources in planetary magnetospheres
  
  • Moore T. E.
  • Fok M.-C. H.
  • Delcourt Dominique
  , 2009.
• Unveiling the nature of phase transitions in the Vlasov limit for a system with longrange interactions
  
  • Firpo Marie-Christine
  , 2009.
• Magnetotail after Geotail, Interball and Cluster: Thin current sheets, fine structure, force balance and stability
  
  • Zelenyi L. M.
  • Malova H. V.
  • Artemyev A. V.
  • Popov V. Y.
  • Petrukovich A. A.
  • Delcourt Dominique
  • Bykov V.
  , 2009, pp.121-170. We present a short review devoted to some scientific achievements in the physics of Earths magnetotail current sheets based on results of Geotail, Interball and Cluster missions. The structure and dynamics of very thin current sheets (TCSs) that are often observed at the night side of the Earths magnetosphere are discussed in details. The development of theoretical ideas and models, stimulated by numerous experimental findings in the terrestrial (and other) magnetospheres, outlined to formulate the state of the art in this field of physics in the pre-THEMIS era.
• On the minimal set of plasma parameters to determine the dispersion law of electron whistler waves
  
  • Lundin B. V.
  • Krafft C.
  Fizika Plazmy / Plasma Physics Reports, MAIK Nauka/Interperiodica, 2009, 35 (6), pp.502-509. The minimal sufficient set of plasma parameters is presented to describe the dispersion properties of electron whistler waves (helicons) in a wide frequency range above the ion cutoff frequency, provided that the wave frequency is significantly lower than the electron plasma frequency. When the gyrofrequency of the lightest ions is much higher than those of heavier ions, it is sufficient to know the relative content of the lightest ions, the highest ion cutoff frequency, the lower hybrid resonance frequency, and the electron gyro- and plasma frequencies. In this case, the frequency of electron whistler waves is determined by the upper root of the biquadratic equation derived, whereas the lower root corresponds to a resonant mode with its refractive index increasing when the frequency tends toward the highest ion gyrofrequency from below. The developed approach is also efficient in plasmas containing a substantial amount of negative ions and/or heavy dust particulates. The accuracy of the approximate solution of the total cold plasma dispersion relation is illustrated graphically. (10.1134/S1063780X09060075)
  DOI : 10.1134/S1063780X09060075
• Universality of Solar-Wind Turbulent Spectrum from MHD to Electron Scales
  
  • Alexandrova Olga
  • Saur J.
  • Lacombe C.
  • Mangeney Anne
  • Mitchell J.
  • Schwartz S. J.
  • Robert Patrick
  Physical Review Letters, American Physical Society, 2009, 103, pp.165003. To investigate the universality of magnetic turbulence in space plasmas, we analyze seven time periods in the free solar wind under different plasma conditions. Three instruments on Cluster spacecraft operating in different frequency ranges give us the possibility to resolve spectra up to 300 Hz. We show that the spectra form a quasiuniversal spectrum following the Kolmogorovs law &#8764;k&#8722;5/3 at MHD scales, a &#8764;k&#8722;2.8 power law at ion scales, and an exponential &#8764;exp&#65279;[&#8722;&#8730;k&#961;e] at scales k&#961;e&#8764;[0.1,1], where &#961;e is the electron gyroradius. This is the first observation of an exponential magnetic spectrum in space plasmas that may indicate the onset of dissipation. We distinguish for the first time between the role of different spatial kinetic plasma scales and show that the electron Larmor radius plays the role of a dissipation scale in space plasma turbulence. (10.1103/PhysRevLett.103.165003)
  DOI : 10.1103/PhysRevLett.103.165003
• Magnetosheath excursion and the relevant transport process at the magnetopause
  
  • Cai C. L.
  • Dandouras I.
  • Rème H.
  • Cao J.B.
  • Zhou G.C.
  • Shen C.
  • Parks G. K.
  • Fontaine Dominique
  Annales Geophysicae, European Geosciences Union, 2009, 27, pp.2997-3005. A large-amplitude excursion of the magnetosheath (MS) in quiet solar wind conditions on 17 March 2004 was recorded simultaneously by the Cluster and TC-1 spacecraft. During this period, the IMF B<SUB>z</SUB> was entirely northward. The coherence between the bow shock motion and magnetopause (MP) motion is revealed and the excursion velocities of the bow shock motion are analyzed. In addition, the relevant plasma transport phenomenon in the form of flux fluctuations below the ion gyrofrequency at the MP is exposed and is interpreted as manifestation of the drift instability. Correlated observations on charge accumulation and electrostatic potential perturbation are recorded by electron measurements in high energy regime, and also the eventual cross-field vortex motion in the nonlinear stage and the consequential mass exchange are exhibited. The present investigation gives some new insight into the MS plasma transport mechanism across the subsolar MP region in quiet solar wind conditions during a period of northward IMF. (10.5194/angeo-27-2997-2009)
  DOI : 10.5194/angeo-27-2997-2009
• Competitive effects of an axial magnetic field and of neutral gas depletion in a positive column
  
  • Liard Laurent
  • Raimbault Jean-Luc
  • Chabert Pascal
  Physics of Plasmas, American Institute of Physics, 2009, 16, pp.053507. Neutral gas dynamics has been incorporated in plasma transport equations in recent studies of nonmagnetized plasma discharge equilibrium. It was found that when the plasma density increases, the neutral gas density becomes depleted in the discharge center, leading to plasma deconfinement. Consequently, larger electron temperature, flatter plasma density profiles, and larger edge-to-center plasma density ratios were observed. In this paper, we investigate the effect of adding a static axial magnetic field to the discharge. We find that at fixed plasma density at the center, the magnetic field reduces the calculated neutral depletion and all the associated effects. Nevertheless, the action of the magnetic field is less pronounced if one keeps the power deposited into the discharge fixed instead. This is because at fixed power, the plasma density increases with the magnetic field. (10.1063/1.3139262)
  DOI : 10.1063/1.3139262