Publications

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
Evaluation of whistler-mode chorus intensification on the nightside during an injection event observed on the THEMIS spacecraft
- Li W.
- Thorne R. M.
- Angelopoulos V.
- Bonnell J. W.
- Mcfadden J. P.
- Carlson C. W.
- Le Contel Olivier
- Roux A.
- Glassmeier K.-H.
- Auster H.-U.
Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2009, 114. The intensification of the nightside whistler-mode chorus emissions is observed in the low-density region outside the plasmapause during the injection of anisotropic plasma sheet electrons into the inner magnetosphere. Time History of Events and Macroscale Interactions During Substorms data of the electron phase space density over the energy range between 0.1 keV and 30 keV are used to develop an analytical model for the distribution of injected suprathermal electrons. The path-integrated gain of chorus waves is then evaluated with the HOTRAY code by tracing whistler-mode chorus waves in a hot magnetized plasma. The simulated wave gain is compared to the observed wave electric field and magnetic field, respectively. The results indicate that lower-energy (<1 keV) plasma sheet electrons can penetrate deeper toward the Earth but cause little chorus intensification, while higher-energy (1 keV to tens of kiloelectron volts) electrons can be injected at relatively higher L-shells and are responsible for the intensification of lower-band and upper-band whistler-mode chorus. Compared to the lower-band chorus, a relatively higher electron anisotropy is required to generate upper-band chorus. In addition, higher plasma density results in stronger wave intensity and a broader frequency band of chorus waves. (10.1029/2008JA013554)
DOI : 10.1029/2008JA013554
Quasi-thermal noise in space plasma: ``kappa'' distributions
- Le Chat G.
- Issautier K.
- Meyer-Vernet N.
- Zouganelis I.
- Maksimovic M.
- Moncuquet M.
Physics of Plasmas, American Institute of Physics, 2009, 16, pp.102903. The transport of energy in collisionless plasmas, especially in space plasmas, is far from being understood. Measuring the temperature of the electrons and their nonthermal properties can give important clues to understand the transport properties. Quasi-thermal noise (QTN) spectroscopy is a reliable tool for measuring accurately the electron density and temperature since it is less sensitive to the spacecraft perturbations than particle detectors. This work models the plasma QTN using a generalized Lorentzian (``kappa'') distribution function for the electrons. This noise is produced by the quasi-thermal fluctuations of the electrons and by the Doppler-shifted thermal fluctuations of the ions. A sum of two Maxwellian functions has mainly been used for modeling the QTN of the electrons, but the observations have shown that the electrons are better fitted by a kappa distribution function. Pioneer work on QTN calculation only considered integer values of kappa. This paper extends these calculations to real values of kappa and gives the analytic expressions and numerical calculations of the QTN with a kappa distribution function. This paper shows some generic properties and gives some practical consequences for plasma wave measurements in space. (10.1063/1.3243495)
DOI : 10.1063/1.3243495
Global Scale-Invariant Dissipation in Collisionless Plasma Turbulence
- Dunlop M. W.
- Sahraoui Fouad
- Kiyani K. H.
- Chapman S. C.
- Khotyaintsev Y. V.
Physical Review Letters, American Physical Society, 2009, 103, pp.075006. A higher-order multiscale analysis of the dissipation range of collisionless plasma turbulence is presented using in situ high-frequency magnetic field measurements from the Cluster spacecraft in a stationary interval of fast ambient solar wind. The observations, spanning five decades in temporal scales, show a crossover from multifractal intermittent turbulence in the inertial range to non-Gaussian monoscaling in the dissipation range. This presents a strong observational constraint on theories of dissipation mechanisms in turbulent collisionless plasmas. (10.1103/PhysRevLett.103.075006)
DOI : 10.1103/PhysRevLett.103.075006
An Observation Linking the Origin of Plasmaspheric Hiss to Discrete Chorus Emissions
- Bortnik J.
- Li W.
- Thorne R. M.
- Angelopoulos V.
- Cully C. M.
- Bonnell J. W.
- Le Contel Olivier
- Roux A.
Science, American Association for the Advancement of Science (AAAS), 2009, 324 (5928), pp.775-778. A long-standing problem in the field of space physics has been the origin of plasmaspheric hiss, a naturally occurring electromagnetic wave in the high-density plasmasphere (roughly within 20,000 kilometers of Earth) that is known to remove the high-energy Van Allen Belt electrons that pose a threat to satellites and astronauts. A recent theory tied the origin of plasmaspheric hiss to a seemingly different wave in the outer magnetosphere, but this theory was difficult to test because of a challenging set of observational requirements. Here we report on the experimental verification of the theory, made with a five-satellite NASA mission. This confirmation will allow modeling of plasmaspheric hiss and its effects on the high-energy radiation environment. (10.1126/science.1171273)
DOI : 10.1126/science.1171273
Magnetic island formation between large-scale flow vortices at an undulating postnoon magnetopause for northward interplanetary magnetic field
- Cully C. M.
- Larson D. E.
- Ergun R. E.
- Roux A.
- Carlson C. W.
- Eriksson S.
- Hasegawa H.
- Teh W.-L.
- Sonnerup B. U. Ö.
- Mcfadden J. P.
- Glassmeier K.-H.
- Le Contel Olivier
- Angelopoulos V.
Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2009, 114. Time History of Events and Macroscale Interactions during Substorms multispacecraft observations are presented for a ~2-h-long postnoon magnetopause event on 8 June 2007 that for the first time indicate that the trailing (sunward) edges of Kelvin-Helmholtz (KH) waves are commonly related to small-scale <0.56 R E magnetic islands or flux transfer events (FTE) during the growth phase of these surface waves. The FTEs typically show a characteristic bipolar B N structure with enhanced total pressure at their center. Most of the small-scale FTEs are not related to any major plasma acceleration. TH-A observations of one small FTE at a transition from the low-latitude boundary layer (LLBL) into a magnetosheath plasma depletion layer were reconstructed using separate techniques that together confirm the presence of a magnetic island within the LLBL adjacent to the magnetopause. The island was associated with a small plasma vortex and both features appeared between two large-scale (~1 R E long and 2000 km wide) plasma vortices. We propose that the observed magnetic islands may have been generated from a time-varying reconnection process in a low ion plasma beta (beta i < 0.2) and low 8.3° field shear environment at the sunward edge of the growing KH waves where the local magnetopause current sheet may be compressed by the converging flow of the large-scale plasma vortices as suggested by numerical simulations of the KH instability. (10.1029/2008JA013505)
DOI : 10.1029/2008JA013505
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.
Electric propulsion using ion-ion plasmas
- Aanesland Ane
- Meige A.
- Chabert Pascal
Journal of Physics: Conference Series, IOP Science, 2009, 162, pp.012009. Recently, we have proposed to use both positive and negative ions for thrust in an electromagnetic space propulsion system. This concept is called PEGASES for Plasma Propulsion with Electronegative GASES and has been patented by the Ecole Polytechnique in France in 2007. The basic idea is to create a stratified plasma with an electron free (ion-ion plasma) region at the periphery of a highly ionized plasma core such that both positive and negative ions can be extracted and accelerated to provide thrust. As the extracted beam is globally neutral there is no need for a downstream neutralizer. The recombination of positive and negative ions is very efficient and will result in a fast recombination downstream of the thruster and hence there is no creation of a plasma plume downstream. The first PEGASES prototype, designed in 2007, has recently been installed in a small vacuum chamber for preliminary tests in our laboratory and the first results have been presented in several conferences. This paper reviews important work that has been used in the process of designing the first PEGASES prototype. (10.1088/1742-6596/162/1/012009)
DOI : 10.1088/1742-6596/162/1/012009
Electron transport coefficients in mixtures of CF4 and CF2 radicals
- Nikitovic Zd
- Stojanovic Vd
- Booth Jean-Paul
- Petrovic Zl
Plasma Sources Science and Technology, IOP Publishing, 2009, 18, pp.035008. Electron kinetics determines the rate of production of chemically active species in processing plasmas. Precise transport coefficients are needed to describe conditions such as those found in plasma assisted technologies for semiconductor production, but these are affected by the density of free radicals, which in themselves depend on the chemical kinetics. We present transport coefficients for electrons in mixtures of CF4 with CF2 (and we also show similar results for other radicals) for ratios of the electric field to the gas number density E/N from 1 to 1000 Td (1 Td = 10−21 V m2). Our analysis of non-conservative collisions revealed a range of E/N where electron attachment to radicals significantly changes the electron kinetics compared with pure CF4 gas. The results are obtained using simple solutions for Boltzmann's equation and exact Monte Carlo simulations. (10.1088/0963-0252/18/3/035008)
DOI : 10.1088/0963-0252/18/3/035008
A novel mechanism for exciting intrinsic toroidal rotation
- Mcdevitt C.J.
- Diamond P.H.
- Gürcan Özgür D.
- Hahm T.S.
Physics of Plasmas, American Institute of Physics, 2009, 16, pp.052302. Beginning from a phase space conserving gyrokinetic formulation, a systematic derivation of parallel momentum conservation uncovers two physically distinct mechanisms by which microturbulence may drive intrinsic rotation. The first mechanism, which emanates from E×B convection of parallel momentum, has already been analyzed [ O. D. Gurcan et al., Phys. Plasmas 14, 042306 (2007) ; R. R. Dominguez and G. M. Staebler, Phys. Fluids B 5, 3876 (1993) ] and was shown to follow from radial electric field shear induced symmetry breaking of the spectrally averaged parallel wave number. Thus, this mechanism is most likely active in regions with steep pressure gradients or strong poloidal flow shear. The second mechanism uncovered, which appears in the gyrokinetic formulation through the parallel nonlinearity, emerges due to charge separation induced by the polarization drift. This novel means of driving intrinsic rotation, while nominally higher order in an expansion of the mode frequency divided by the ion cyclotron frequency, does not depend on radial electric field shear. Thus, while the magnitude of the former mechanism is strongly reduced in regions of weak radial electric field shear, this mechanism remains unabated and is thus likely relevant in complementary regimes. (10.1063/1.3122048)
DOI : 10.1063/1.3122048
Cross-scale: multi-scale coupling in space plasmas
- Schwartz S. J.
- Horbury T.
- Owen C.
- Baumjohann W.
- Nakamura R.
- Canu Patrick
- Roux A.
- Sahraoui Fouad
- Louarn P.
- Sauvaud J.-A.
- Pinçon Jean-Louis
- Vaivads A.
- Marcucci M. F.
- Anastasiadis A.
- Fujimoto M.
- Escoubet P.
- Taylor M.
- Eckersley S.
- Allouis E.
- Perkinson M.-C.
Experimental Astronomy, Springer Link, 2009, 23, pp.1001-1015. Most of the visible universe is in the highly ionised plasma state, and most of that plasma is collision-free. Three physical phenomena are responsible for nearly all of the processes that accelerate particles, transport material and energy, and mediate flows in systems as diverse as radio galaxy jets and supernovae explosions through to solar flares and planetary magnetospheres. These processes in turn result from the coupling amongst phenomena at macroscopic fluid scales, smaller ion scales, and down to electron scales. Cross-Scale, in concert with its sister mission SCOPE (to be provided by the Japan Aerospace Exploration AgencyJAXA), is dedicated to quantifying that nonlinear, time-varying coupling via the simultaneous in-situ observations of space plasmas performed by a fleet of 12 spacecraft in near-Earth orbit. Cross-Scale has been selected for the Assessment Phase of Cosmic Vision by the European Space Agency. (10.1007/s10686-008-9085-x)
DOI : 10.1007/s10686-008-9085-x
Plasma discharge inside water
- Ceccato P H
- Guaitella Olivier
- Rousseau Antoine
, 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
Investigation of InP etching mechanisms in a Cl2/H2 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
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
Influence of dielectric material in Dielectric Barrier Discharge (DBD) for chemistry reactivity control
- Youssef Joseph
- Bouamra K.
- Makarov M.
- Guaitella Olivier
- Rousseau Antoine
, 2009.
Influence of dielectric material on chemistry reactivity in Dielectric Barrier Discharge (DBD)
- Youssef Joseph
- Bouamra K.
- Makarov M.
- Guaitella Olivier
- Rousseau Antoine
, 2009.
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.
New insights on Titan's plasma-driven Schumann resonance inferred from Huygens and Cassini data
- Béghin Christian
- Canu Patrick
- Karkoschka E.
- Sotin C.
- Bertucci C.
- Kurth W.S.
- Berthelier Jean-Jacques
- Grard R.
- Hamelin Michel
- Schwingenschuh K.
- Simões Fernando
Planetary and Space Science, Elsevier, 2009, 57 (14-15), pp.1872-1888. (10.1016/j.pss.2009.04.006)
DOI : 10.1016/j.pss.2009.04.006
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 RE 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
Wave emissions at half electron gyroharmonics in the equatorial plasmasphere region: CLUSTER observations and statistics
- El-Lemdani Mazouz F.
- Rauch Jean-Louis
- Décréau Pierrette
- Trotignon Jean-Gabriel
- Vallières Xavier
- Darrouzet F.
- Canu Patrick
- Suraud X.
Advances in Space Research, Elsevier, 2009, 43 (2), pp.253-264. Intense (n 1/2) fce emissions are a common phenomenon observed in the terrestrial inner magnetosphere. One of their interests is their possible effect in the pitch angle scattering of plasmasheet keV-electron, leading to diffuse auroras. In this paper, we present CLUSTERs point of view about this topic, in the equatorial region of the plasmasphere, via a statistical study using 3 years of data. Spectral characteristics of these waves, which represent an important clue concerning their generation mechanism, are obtained using WHISPER data near perigee. Details on the wave spectral signature are shown in an event study, in particular their splitting in fine frequency bands. The orbit configuration of the four spacecraft offers a complete sampling on all MLT sectors. A higher occurrence rate of the emissions in the dawn sector and their confinement to the geomagnetic equator, pointed out in previous studies, are confirmed and described with additional details. The proximity of emission sites, both to the plasmapause layer and to the geomagnetic equator surface, seems to be of great importance in the behaviour of the (n 1/2) fce wave characteristics. Our study indicates for the first time, that both the intensity of (n 1/2) fce emissions, and the number of harmonic bands they cover, are increasing as the observation point is located further away outside from the plasmapause layer. Moreover, a study of the wave intensity in the first harmonic band (near 3/2 fce) shows higher amplitude for these emissions than previous published values, these emissions can play a role in the scattering of hot electrons. Finally, geomagnetic activity influence, studied via time series of the Dst index preceding observations, indicates that (n 1/2) fce emission events are observed at CLUSTER position under moderate geomagnetic activity conditions, no specific Dst time variation being required. (10.1016/j.asr.2008.06.007)
DOI : 10.1016/j.asr.2008.06.007
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
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
Regeneration of adsorbent/catalytic material by a Dielectric Barrier Discharge (DBD)
- Youssef Joseph
- Bouamra K.
- Makarov M.
- Guaitella Olivier
- Rousseau Antoine
, 2009.

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