Publications

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
• 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
• Plasma discharge inside water
  
  • Ceccato P H
  • Guaitella Olivier
  • Rousseau Antoine
  , 2009.
• Cascade models in plasma turbulence: The role of sheared flows
  
  • Gürcan Özgür D.
  • Garbet X.
  • Hennequin Pascale
  • Diamond P.H.
  • Casati A.
  , 2009 (oral).
• Plasma sheet circulation pathways
  
  • Moore T. E.
  • Fok M.-C. H.
  • Delcourt Dominique
  • Slinker Steve P.
  • Damiano P.
  , 2009.
• 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
• 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.
• 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
• 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
• 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
• 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.
• 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
• 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
• Role of internal plasma sources in planetary magnetospheres
  
  • Moore T. E.
  • Fok M.-C. H.
  • Delcourt Dominique
  , 2009.
• Time resolved studies on pulsed DC discharges using QCL
  
  • Welzel S.
  • Guaitella Olivier
  • Lazzaroni Claudia
  • Gatilova Lina
  • Rousseau Antoine
  • Roepcke J.
  , 2009.
• Time resolved shadow imaging of a pulsed corona in water
  
  • Ceccato P H
  • Guaitella Olivier
  • Rousseau Antoine
  , 2009.
• Dielectric Barrier Discharge (DBD) and Zeolite Coupling: Butane case
  
  • Youssef Joseph
  • Bouamra K.
  • Makarov M.
  • Guaitella Olivier
  • Rousseau Antoine
  , 2009.
• Quantum Cascade Laser Absorption Spectroscopy Study on the Influence of Plasma Stimulated Surface Adsorptions to the NO Destruction Kinetics
  
  • Hübner M.
  • Guaitella Olivier
  • Rousseau Antoine
  • Welzel S.
  • Roepcke J.
  , 2009.
• West African equatorial ionospheric parameters climatology based on Ouagadougou ionosonde station data from June 1966 to February 1998
  
  • Ouattara F.
  • Amory-Mazaudier Christine
  • Fleury Rolland
  • Lassudrie Duchesne Patrick
  • Vila P.
  • Petitdidier Monique
  Annales Geophysicae, European Geosciences Union, 2009, 27 (6), pp.2503-2514. This study is the first which gives the climatology of West African equatorial ionosphere by using Ouagadougou station through three solar cycles. It has permitted to show the complete morphology of ionosphere parameters by analyzing yearly variation, solar cycle and geomagnetic activity, seasonal evolution and diurnal development. This work shows that almost all ionospheric parameters have 11-year solar cycle evolution. Seasonal variation shows that only foF2 exhibits annual, winter and semiannual anomaly. foF2 seasonal variation has permitted us to identify and characterize solar events effects on F2 layer in this area. In fact (1) during quiet geomagnetic condition foF2 presents winter and semiannual anomalies asymmetric peaks in March/April and October. (2) The absence of winter anomaly and the presence of equinoctial peaks are the most visible effects of fluctuating activity in foF2 seasonal time profiles. (3) Solar wind shock activity does not modify the profile of foF2 but increases ionization. (4) The absence of asymmetry peaks, the location of the peaks in March and October and the increase of ionization characterize recurrent storm activity. F1 layers shows increasing trend from cycle 20 to cycle 21. Moreover, E layer parameters seasonal variations exhibit complex structure. It seems impossible to detect fluctuating activity effect in E layer parameters seasonal variations but shock activity and wind stream activity act to decrease E layer ionization. It can be seen from Es layer parameters seasonal variations that wind stream activity effect is fairly independent of solar cycle. E and Es layers critical frequencies and virtual heights diurnal variations let us see the effects of the greenhouse gases in these layers. (10.5194/angeo-27-2503-2009)
  DOI : 10.5194/angeo-27-2503-2009