Publications

2012

• Variability of ULF wave power at the magnetopause: a study at low latitude with Cluster data
  
  • Cornilleau-Wehrlin Nicole
  • Grison B.
  • Belmont Gérard
  • Rezeau Laurence
  • Chanteur Gérard
  • Robert Patrick
  • Canu Patrick
  , 2012, 14, pp.9562. Strong ULF wave activity has been observed at magnetopause crossings since a long time. Those turbulent-like waves are possible contributors to particle penetration from the Solar Wind to the Magnetosphere through the magnetopause. Statistical studies have been performed to understand under which conditions the ULF wave power is the most intense and thus the waves can be the most efficient for particle transport from one region to the other. Clearly the solar wind pressure organizes the data, the stronger the pressure, the higher the ULF power (Attié et al 2008). Double STAR-Cluster comparison has shown that ULF wave power is stronger at low latitude than at high latitude (Cornilleau-Wehrlin et al, 2008). The different studies performed have not, up to now, shown a stronger power in the vicinity of local noon. Nevertheless under identical activity conditions, the variability of this power, even at a given location in latitude and local time is very high. The present work intends at understanding this variability by means of the multi spacecraft mission Cluster. The data used are from spring 2008, while Cluster was crossing the magnetopause at low latitude, in particularly quite Solar Wind conditions. The first region of interest of this study is the sub-solar point vicinity where the long wavelength surface wave effects are most unlikely.
• Solar Wind Interaction with Mercury's Magnetosphere: a Simulation Study
  
  • Richer Emilie
  • Chanteur Gérard
  • Modolo Ronan
  • Leblanc François
  • Hess Sebastien
  , 2012, 14, pp.EGU2012-8178. Three flybys of Mercury by Mariner 10, numerous terrestrial observations of Mercury's exosphere and MESSENGER observations during flybys and orbital operations have brought important information about the Hermean environment. Mercury's intrinsic magnetic field is principally dipolar and its interaction with the Solar Wind (SW) creates a small and very dynamic magnetosphere. Mercury's exosphere is a highly variable and complex neutral environment made of several species: H, He, O, Na, K, Ca, and Mg have already been detected. MESSENGER is in orbit around Mercury, since March 2011, with a polar trajectory and a periapsis located near the north geographic pole. MESSENGER observations lead to a new description of the source of the intrinsic magnetic field : a northward shifted dipole of 500 km seems to better fit the magnetic field observations at northern latitudes higher than 30°, than former models (Anderson et al, 2011). However the lack of low altitude observations above the southern hemisphere does not allow definitive conclusions about the topology of the planetary magnetic field at high southern latitudes. Global simulations can provide complementary information of Mercury's magnetic field structure and its global interaction with the solar wind. This study presents simulation results from a 3-dimensional parallel multi-species hybrid model of Mercury's magnetosphere interaction with the SW. The SW in this model is representative of conditions at Mercury's aphelion (0.47AU) and is composed of 95% protons and 5% alpha particles. The simulated IMF is oriented accordingly to observations during the orbit of MESSENGER on April 23rd of 2011 without component in the north/south direction and a cone angle of about 60°. In addition a neutral corona of sodium is included in this model and is partly ionized by solar photons. Planetary and SW plasmas are treated separately and the dynamic of each ion species can be investigated separately. Simulations have been performed on a grid of 186×400×400 cells with a spatial resolution of Deltax~120km. Two models of the source of the internal magnetic field are tested: 1/ a northward shifted dipole, according to Anderson et al, 2011, 2/ a combination of a centered dipole and quadrupole fitted to the shifted dipole in order to comply with MESSENGER observations above 50°N latitudes. We emphasize differences between the two southern magnetospheres resulting from the two different models of the internal field.
• Solar wind turbulence at kinetic scales
  
  • Alexandrova O.
  • Rossi C.
  • Mangeney A.
  • Grappin Roland
  • Carbone V.
  , 2012, 14, pp.9963. Solar wind is a turbulent magnetized collisionless plasma. Kolmogorov's turbulent spectrum is widely observed at magnetohydrodynamic scales. At smaller scales, i.e. at scales of the order of the kinetic plasma scales (such as Larmor radii of charged particles or their inertial lengths, ~ 50 km for protons and ~ 2 km for electrons), turbulence is less studied and is a matter of debate. In this presentation we review different observations related to kinetic range, such as magnetic spectra, signatures of multi- and mono-fractality, wave vector anisotropy and indications of different wave modes. Then, we will show new results related to intermittency and coherent structures present within this range.
• Origin of the different energetic ion populations in the quasi-perpendicular Ion Foreshock: 2D Full-particle simulation
  
  • Savoini Philippe
  • Lembège Bertrand
  • Stienlet J.
  , 2012. The foreshock region is located upstream of the terrestrial bow shock and is characterized by energetic backstreaming particles (electrons and ions) issued from the shock and by an important wave activity as observed by many space missions. In order to analyse the foreshock region, a curved shock is simulated with the help of a 2 - D full particle (PIC) code, where full curvature and time of flight effects, and where both electrons and ions dynamics are fully described by a self consistent approach. The analysis is presently restricted to the quasi-perpendicular angular range defined by 45°≤ θBn ≤ 90°, where θBn is the angle between the shock normal and the upstream magnetostatic field, and we focus only on the ion foreshock. In a good agreement with experimental data, present preliminary results evidence two distinct ion populations collimated along the interplanetary magnetic field (IMF): (i) the Field-Aligned Beam population (hereafter named "FAB") and (ii) the gyro-phase bunch population (hereafter named "GPB") which differ from each other by their gyrotropic or non-gyrotropic behavior, respectively. Additionally, the "FAB" population is observed at the edge of the ion foreshock and near the curved shock front, while the "'GPB" population is observed deeper in the foreshock and further from the shock front. The analysis shows that no pitch angle scattering mechanism needs to be invoked to account for the generation of the "GPB", but rather additional criteria are necessary namely: the interaction time Δtint of backstreaming ions with the shock front and their downstream penetration depth. These criteria allow to evidence that (i) the "FAB" population corresponds to particles which move back and forth between the upstream edge of the front and the overshoot, and are characterized by a quite large Δtint (covering several local gyro-periods, 4 ≤ τci ≤ 12). In contrast, (ii) the "GPB" ions have suffered a very short interaction time (i.e. Δtint < 1τci) and escaped into the upstream region with a parallel velocity slightly higher than the "FAB" population. Finally, we observe that the "FAB" population may have different origins, and come even from the downstream region (i.e. so called "leaked" ions), although all "GPB" particles seem to be produced by the electrostatic field built up at the shock front and are emitted in a burst-like mode rather than in continuous way.
• On the origin of the 1/f spectrum in the heliosphere
  
  • Verdini Andrea
  • Grappin Roland
  • Velli Marco
  , 2012, 14, pp.13293. We present results of numerical simulations in which the low frequency 1/f spectrum is a natural outcome of the turbulent dynamics inside the sub-Alfvenic solar wind. The magnetic field is assumed to be parallel to the radial expanding solar wind, a situation that holds at that short heliospheric distance. We inject fluctuations of short or long periodicity (T=600 or 6000 s) at the base of the chromosphere and study the properties of the resulting (perpendicular and parallel) spectrum that is advected by the solar wind outside the Alfvenic critical point. The formation of the 1/f spectrum is due to the recycling of Alfvenic turbulence between the transition region and the Alfvenic critical point, a mechanism that works thanks to the high Alfven speed in the low corona and the relatively weak nonlinear interactions there. The perpendicular magnetic spectrum is found to be always a power-law with a slope close to the Kolmogorov value 5/3. The parallel magnetic spectrum shows a double-power-law with slopes depending on the turbulence strength and on the width of the injected spectrum. The latter also determines the frequency of the spectral break. Slopes approximately -1 and -2 at low and high frequencies respectively are found for weak turbulence and wide injected spectrum (T=600 s). A stronger turbulence causes a flattening of the low-frequency slope, a narrower injected spectrum decreases the frequency of the spectral break. This offers the possibility to deduce the form of the chromospheric spectrum from measurements made just outside the Alfvenic critical point. We suggest that the double-power-law spectrum measured by Helios at 0.3 AU, where the average magnetic field is not aligned with radial direction, results from the combination of the different spectral slopes. At low frequency the parallel spectrum dominates with its characteristic 1/f shape, while at higher frequencies its steep spectral slope (-2) is masked by the more energetic perpendicular spectrum (with a -5/3 slope). Given the location of the frequency break, according to the above mechanism, the 1/f spectrum is a signature of a weak turbulent activity in the corona and a wide seed-spectrum in the chromosphere.
• Vulnerability of optical detection systems to megajoule class laser radiative environment
  
  • Rousseau Adrien
  • Darbon Stéphane
  • Girard S.
  • Paillet P.
  • Bourgade J.-L.
  • Goiffon V.
  • Magnan P.
  • Lalucaa V.
  • Hamel M.
  • Larour Jean
  , 2012, 8439. The Laser MegaJoule (LMJ) facility will host inertial confinement fusion experiments in order to achieve ignition by imploding a Deuterium-Tritium filled microballoon [1]. In this context an X-ray imaging system is necessary to diagnose the core size and the shape of the target in the 10-100 keV band. Such a diagnostic will be composed of two parts: an X-ray optical system and a detection assembly. The survivability of each element of this diagnostic has to be ensured within the mixed pulse consisting of X-rays, gamma rays and 14 MeV neutrons created by fusion reactions. The design of this diagnostic will take into account optics and detectors vulnerability to neutron yield of at least 1016. In this work, we will present the main results of our vulnerability studies and of our hardening-by-system and hardening-by- design studies.
• High-voltage Tesla coil discharges triggered and guided by femtosecond laser filaments in air
  
  • Brelet Yohann
  • Houard Aurélien
  • Forestier Benjamin
  • Carbonnel Jérôme
  • Liu Y.
  • André Y-B.
  • Prade Bernard S.
  • Arantchouk Léonid
  • Mysyrowicz André
  , 2012.
• Modulation of GAM frequency observed on Tore Supra using Doppler backscattering
  
  • Vermare Laure
  • Hennequin Pascale
  • Gürcan Özgür D.
  • Storelli A.
  • Tore Supra Team
  , 2012, oral.
• Spectral dynamics and Predator-Prey oscillations in simple (and more complicated) models of plasma turbulence
  
  • Gürcan Özgür D.
  , 2012 (oral).
• Cinétique d'allumage par plasma nanoseconde [Kinetics of ignition by nanosecond plasma]
  
  • Starikovskaia Svetlana
  , 2012.
• ETUDE ET MISE EN OEUVRE DE MAGNETORESISTANCES ANISOTROPES ET A EFFET TUNNEL POUR LA MESURE DES CHAMPS MAGNETIQUES FAIBLES DANS LES PLASMAS SPATIAUX
  
  • Mansour Malik
  , 2012. L'étude in situ des relations Soleil-Terre et plus généralement des environnements ionisés du système solaire, nécessite la mesure d'ondes qui se propagent dans un plasma magnétisé. A bord des observatoires spatiaux, la composante magnétique de ces ondes est obtenue à l'aide de magnétomètres à induction. La mesure des hautes fréquences (de quelques Hz à quelques 100 kHz) est réalisée par des magnétomètres Searchcoil tandis que celles des basses fréquences (de quelques 10 mHz à quelques Hz) et de la composante continue sont confiées aux magnétomètres Fluxgate. Cette thèse porte sur le développement d'un magnétomètre dont la bande de mesure s'étend du continu à plusieurs kiloHertz. On y présente un concept instrumental innovant reposant sur la mise en œuvre simultanée d'une mesure inductive et magnétorésistive du champ magnétique. Nous nous intéressons d'abord à la conception et à l'étude de capteurs à magnétorésistance anisotrope (AMR) et à magnétorésistance tunnel (TMR) dont les propriétés d'anisotropie sont contrôlées par couplage d'échange. Nous montrons ensuite comment ces magnétorésistances peuvent être intégrées à un magnétomètre Searchcoil dont le noyau ferromagnétique est mis à profit pour réaliser un concentrateur magnétique performant. Nous détaillons alors les différents aspects de la conception d'un magnétomètre hybride Searchcoil/Magnétorésistance répondant aux contraintes environnementales associées aux expériences spatiales ainsi que d'un outil original d'optimisation des performances, alliant un modèle par éléments finis à un algorithme de type génétique. Nous prouvons enfin la faisabilité du concept proposé en réalisant un premier prototype de magnétomètre hybride Searchcoil/Capteur PHE tri-axes et de son électronique de préamplification faible bruit. La sensibilité de ce prototype, testé en conditions réelles lors d'un tir de fusée scientifique, avoisine les 200 fT/sqrt (Hz) à 1 kHz et les 400 pT/sqrt (Hz) à 1 Hz.
• Wave turbulence and flow self organization in magnetized fusion plasmas
  
  • Gürcan Özgür D.
  , 2012. http://www.lps.ens.fr/recherche/physique-non-lineaire/waveturb/waveturb/Bienvenue.html
• Seeing Inside Plasma Etch Reactors: from diagnostics to sensors for control
  
  • Booth Jean-Paul
  , 2012.
• Chlorine atom and molecule dynamics in an inductively coupled plasma in pure Cl<SUB>2</SUB>
  
  • Booth Jean-Paul
  • Chabert Pascal
  • Azamoum Yasmina
  • Sirse Nishant
  , 2012.
• Modélisation de linteraction entre le vent solaire et la magnétosphère de Mercure
  
  • Richer Emilie
  • Modolo Ronan
  • Chanteur Gérard
  • Leblanc François
  • Hess Sebastien
  , 2012.
• Simulation 2D PIC auto-cohérent d'un choc courbe et du préchoc ionique associé : analyse des différentes populations ioniques énergétiques
  
  • Savoini Philippe
  • Lembège Bertrand
  • Stienlet J.
  , 2012.
• Physics of low pressure radio-frequency plasmas
  
  • Chabert Pascal
  , 2012. http://www.plasma.engg.nagoya-u.ac.jp/IC-2012
• Induction Magnetometers Principle, Modeling and Ways of Improvement
  
  • Coillot Christophe
  , 2012, pp.1-21. This book provides an introductory overview of the research done in recent years in the area of magnetic sensors. The topics presented in this book range from fundamental theories and properties of magnets and their sensing applications in areas such as biomedicine, microelectromechanical systems, nano-satellites and pedestrian tracking. Written for the readers who wished to obtain a basic understanding of the research area as well as to explore other potential areas of applications for magnetic sensors, this book presents exciting developments in the field in a highly readable manner. (10.5772/38945)
  DOI : 10.5772/38945
• Modélisation de l'environnement plasma martien : couplage entre espèces neutres et chargées
  
  • Leblanc François
  • Modolo Ronan
  • Hess Sebastien
  • Yagi M.
  • Chaufray Jean-Yves
  • Forget F.
  • Mazelle C.
  • Gonzales-Galindo F.
  • Grimal S.
  • Chanteur Gérard
  , 2012. Le vent solaire interagit fortement avec Mars et contribue à l'érosion de son enveloppe gazeuse et participe à la dynamique atmosphérique. Le couplage électromagnétique avec ces environnements neutres a lieu au travers des processus d'ionisation qui agissent comme catalyseur : l'ionisation par les photons solaires, les échanges de charges, et l'ionisation par impact électronique de leurs hautes atmosphères et leurs exosphères. Un modèle 3D décrivant la dynamique des plasmas vent solaire et planétaire au voisinage de la planète a été développé (Modolo et al, 2005, 2006, 2012) puis parallélisé dans le cadre du projet HELIOSARES (PI : F. Leblanc). Cette parallélisation permet de décrire l'environnement ionisé de Mars, de 150 km d'altitude à une dizaine de rayons martiens avec une résolution spatiale de 80 km. Ce modèle est complété par une description ionosphérique simplifiée, qui par la suite pourra être remplacée par les résultats du modèle ionosphérique GCM-LMD (Chaufray, Gonzalez-Galindo, Forget et al). Les résultats du modèle magnétosphérique (hybride) et l'échappement sont discutés. Les premiers essais d'un couplage entre un modèle exosphérique thermiques 3D (Yagi, Leblanc et al) et le modèle magnétosphérique sont également abordés.
• Solar wind and geomagnetism: toward a standard classification of geomagnetic activity from 1868 to 2009
  
  • Zerbo Jean-Louis
  • Amory-Mazaudier Christine
  • Ouattara Frédéric Martial
  • Richardson J.D.
  Annales Geophysicae, European Geosciences Union, 2012, pp.1-6. We examined solar activity with a large series of geomagnetic data from 1868 to 2009. We have revisited the geomagnetic activity classification scheme of Legrand and Simon (1989) and improve their scheme by lowering the minimum Aa index value for shock and recurrent activity from 40 to 20 nT. This improved scheme allows us to clearly classify about 80% of the geomagnetic activity in this time period instead of only 60% for the previous Legrand and Simon classification. (10.5194/angeo-30-421-2012)
  DOI : 10.5194/angeo-30-421-2012
• Seasonal, Diurnal, and Solar-Cycle Variations of Electron Density at TwoWest Africa Equatorial Ionization Anomaly Stations
  
  • Ouattara Frédéric Martial
  • Gnabahou Doua Allain
  • Amory-Mazaudier Christine
  International Journal of Geophysics, Hindawi Publishing Corporation, 2012, 2012, pp.1-10. We analyse the variability of foF2 at two West Africa equatorial ionization anomaly stations (Ouagadougou and Dakar) during three solar cycles (from cycle 20 to cycle 22), that is, from 1966 to 1998 for Ouagadougou and from 1971 to 1997 for Dakar. We examine the effect of the changing levels of solar extreme ultraviolet radiation with sunspot number. The study shows high correlation between foF2 and sunspot number (Rz). The correlation coefficient decreases from cycle 20 to cycle 21 at both stations. From cycle 21 to cycle 22 it decreases at Ouagadougou station and increases at Dakar station. The best correlation coefficient, 0.990, is obtained for Dakar station during solar cycle 22. The seasonal variation displays equinoctial peaks that are asymmetric between March and September. The percentage deviations of monthly average data from one solar cycle to another display variability with respect to solar cycle phase and show solar ultraviolet radiation variability with solar cycle phase. The diurnal variation shows a noon bite out with a predominant late-afternoon peak except during the maximum phase of the solar cycle. The diurnal Ouagadougou station foF2 data do not show a significant difference between the increasing and decreasing cycle phases, while Dakar station data do show it, particularly for cycle 21. The percentage deviations of diurnal variations from solar-minimum conditions show more ionosphere during solar cycle 21 at both stations for all three of the other phases of the solar cycle. There is no significant variability of ionosphere during increasing and decreasing solar cycle phases at Ouagadougou station, but at Dakar station there is a significant variability of ionosphere during these two solar-cycle phases. (10.1155/2012/640463)
  DOI : 10.1155/2012/640463
• Plasma pour la medicine
  
  • Marinov Ilya
  • Guaitella Olivier
  • Rousseau Antoine
  • Starikovskaia Svetlana
  , 2012.
• Plasma deposition of nanocrystalline silicon for solar cells : RF waveform tailoring to optimize deposition rate and film morphology
  
  • Booth Jean-Paul
  • Johnson E.V.
  • Delattre Pierre-Alexandre
  , 2012.
• Alpha particle redistribution due to experimentally reconstructed internal kink modes
  
  • Farengo R
  • Ferrari H E
  • Firpo Marie-Christine
  • Garcia-Martinez P L
  • Lifschitz Agustin
  Plasma Physics and Controlled Fusion, IOP Publishing, 2012, 54 (2), pp.025007. The redistribution of alpha particles due to internal kink modes is calculated. The exact particle trajectories in the total, equilibrium plus perturbation, fields are calculated. The equilibrium magnetic field is obtained by analytically solving the Grad–Shafranov equation. The perturbed electric and magnetic fields are reconstructed using the experimental information about the displacement eigenfunction. An effective diffusion coefficient is introduced to quantify the magnitude of the particle redistribution produced by the perturbations. (10.1088/0741-3335/54/2/025007)
  DOI : 10.1088/0741-3335/54/2/025007
• Simulation study of solar wind interaction with Mercurys magnetosphere
  
  • Richer Emilie
  • Modolo Ronan
  • Chanteur Gérard
  • Hess Sebastien
  • Allioux Renaud
  • Leblanc François
  , 2012.