Publications

2011

• Statistical study of the DP2 enhancement at the dayside dip-equator compared to low latitudes
  
  • Mene N.M.
  • Kobea A. T.
  • Obrou O.K.
  • Zaka K.Z.
  • Boka K.
  • Amory-Mazaudier Christine
  • Assamoi P.
  Annales Geophysicae, European Geosciences Union, 2011, pp.1-9. It has been largely investigated and established that the DP2 events are enhanced at dip-equator compared to low latitudes. Studies by several authors showed various enhancement ratio values of DP2 amplitude at the dayside dipequator relative to those at low latitudes. In order to quantify this enhancement ratio, we carried out a statistical study on this phenomenon using the ground magnetometer data at locations ranging from polar cap to dip-equator over the African, Asian and American sector. Our result gave an enhancement ratio which shows a diurnal variation with a maximum value around 12:00 LT and is correlated with the regular variation of the geomagnetic H-component. The longitudinal variation of the enhancement ratio of the DP2 exhibits high values over the American sector compared to Asian sector and African sector which have lowest values. This longitudinal dependence is similar to that of the equatorial electrojet magnetic effect. (10.5194/angeo-29-2225-2011)
  DOI : 10.5194/angeo-29-2225-2011
• Observations of whistler-mode chorus in a large range of radial distances
  
  • Santolík O.
  • Macusova E.
  • Gurnett D. A.
  • Pickett J. S.
  • Cornilleau-Wehrlin Nicole
  , 2011, 22, pp.A5. Whistler-mode chorus emissions are known for their capacity to interact with energetic electrons. We use data collected by the Cluster mission after 2005, when the orbit of the four Cluster spacecraft changed, thus facilitating the analysis of chorus in a large range of different radial distances from the Earth. We concentrate our analysis on the equatorial source region of chorus. We use multipoint measurements of the WBD and STAFF-SA instruments to characterize propagation and spectral properties of the observed waves. We show that intense whistler-mode emissions are found at large radial distances up to the dayside magnetopause. These emissions either have the form of hiss or they contain the typical structure of chorus wave packets. This result is supported by case studies as well as by statistical results, using the unprecedented database of Cluster measurements.
• Generalized Analysis Tools for Multi-Spacecraft Missions
  
  • Chanteur Gérard
  , 2011, 31, pp.1952. Analysis tools for multi-spacecraft missions like CLUSTER or MMS have been designed since the end of the 90's to estimate gradients of fields or to characterize discontinuities crossed by a cluster of spacecraft. Different approaches have been presented and discussed in the book "Analysis Methods for Multi-Spacecraft Data" published as Scientific Report 001 of the International Space Science Institute in Bern, Switzerland (G. Paschmann and P. Daly Eds., 1998). On one hand the approach using methods of least squares has the advantage to apply to any number of spacecraft [1] but is not convenient to perform analytical computation especially when considering the error analysis. On the other hand the barycentric approach is powerful as it provides simple analytical formulas involving the reciprocal vectors of the tetrahedron [2] but appears limited to clusters of four spacecraft. Moreover the barycentric approach allows to derive theoretical formulas for errors affecting the estimators built from the reciprocal vectors [2,3,4]. Following a first generalization of reciprocal vectors proposed by Vogt et al [4] and despite the present lack of projects with more than four spacecraft we present generalized reciprocal vectors for a cluster made of any number of spacecraft : each spacecraft is given a positive or nul weight. The non-coplanarity of at least four spacecraft with strictly positive weights is a necessary and sufficient condition for this analysis to be enabled. Weights given to spacecraft allow to minimize the influence of some spacecraft if its location or the quality of its data are not appropriate, or simply to extract subsets of spacecraft from the cluster. Estimators presented in [2] are generalized within this new frame except for the error analysis which is still under investigation. References [1] Harvey, C. C.: Spatial Gradients and the Volumetric Tensor, in: Analysis Methods for Multi-Spacecraft Data, G. Paschmann and P. Daly (eds.), pp. 307-322, ISSI SR-001, 1998. [2] Chanteur, G.: Spatial Interpolation for Four Spacecraft: Theory, in: Analysis Methods for Multi-Spacecraft Data, G. Paschmann and P. Daly (eds.), pp. 371-393, ISSI SR-001, 1998. [3] Chanteur, G.: Accuracy of field gradient estimations by Cluster: Explanation of its dependency upon elongation and planarity of the tetrahedron, pp. 265-268, ESA SP-449, 2000. [4] Vogt, J., Paschmann, G., and Chanteur, G.: Reciprocal Vectors, pp. 33-46, ISSI SR-008, 2008.
• A prototype of Virtual Observatory access for planetary data in the framework of Europlanet-RI/IDIS
  
  • Gangloff M.
  • Cecconi Baptiste
  • Bourrel N.
  • Jacquey C.
  • Le Sidaner Pierre
  • Berthier J.
  • Andre N.
  • Pallier E.
  • Erard S.
  • Aboudarham J.
  • Chanteur Gérard
  • Capria Maria Teresa
  • Khodachenko Maxim L.
  • Manaud N.
  • Schmidt Walter
  • Schmitt B.
  • Topf F.
  • Trautan F.
  • Sarkissian Alain
  , 2011, 21, pp.abstract id.SM21A-1995. Europlanet RI is a four-year project supported by the European Union under the Seventh Framework Programme. Launched in January 2009, it is an Integrated Infrastructure Initiative, ie. A combination of Networking Activities, Transnational Access Activities and Joint Research Activities. The Networking Activities aim at further fostering a culture of cooperation in the field of Planetary Sciences. The objective of the Transnational Access Activities is to provide transnational access to a range of laboratory and field site facilities tailored to the needs of planetary research and on-line access to the available planetary science data, information and software tools, through the IDIS e-service. The overall aim of the Joint Research Activities (JRA) is to improve the services provided by the ensemble of Transnational Access Activities. In EuroPlaNet-RI, JRA4 must prepare essential tools for IDIS (Integrated and Distributed Information Service) allowing the planetary science community to interrogate some selected data centres, access and process data and visualize the results. This is the first step towards a Planetary Virtual Observatory. The first requirement for different data centres to be able to operate together collectively is adequate standardization. In particular a common description of data and services is essential. This is why the major part of JRA4/Task2 activity is focussing on data models, associated dictionnaries, and protocols to exchange queries. A specific data model is being developed for IDIS, associated with the PDAP protocol, a standard defined by the IPDA (International Planetary Data Alliance) The scope of this prototype is to demonstrate the capabilities of the IDIS Data Model, and the PDAP protocol to search and retrieve data in the wide topical planetology context.
• Propagation of EMIC triggered emissions toward the magnetic equatorial plane
  
  • Grison B.
  • Santolík O.
  • Pickett J. S.
  • Omura Y.
  • Engebretson M. J.
  • Dandouras I. S.
  • Masson A.
  • Décréau Pierrette
  • Cornilleau-Wehrlin Nicole
  , 2011, 13, pp.B2068. EMIC triggered emissions are observed close to the equatorial plane of the magnetosphere at locations where EMIC waves are commonly observed: close to the plasmapause region and in the dayside magnetosphere close to the magnetopause. Their overall characteristics (frequency with time dispersion, generation mechanism) make those waves the EMIC analogue of rising frequency whistler-mode chorus emissions. In our observations the Poynting flux of these emissions is usually clearly arriving from the equatorial region direction, especially when observations take place at more than 5 degrees of magnetic latitude. Simulations have also confirmed that the conditions of generation by interaction with energetic ions are at a maximum at the magnetic equator (lowest value of the background magnetic field along the field line). However in the Cluster case study presented here the Poynting flux of EMIC triggered emissions is propagating toward the equatorial region. The large angle between the wave vector and the background magnetic field is also unusual for this kind of emission. The rising tone starts just above half of the He gyrofrequency (Fhe ) and it disappears close to Fhe . At the time of detection, the spacecraft magnetic latitude is larger than 10 degrees and L shell is about 4. The propagation sense of the emissions has been established using two independent methods: 1) sense of the parallel component of the Poynting flux for a single spacecraft and 2) timing of the emission detections at each of the four Cluster spacecraft which were in a relatively close configuration. We propose here to discuss this unexpected result considering a reflection of this emission at higher latitude.
• Field-aligned acceleration above the polar caps during prolonged periods of Northward IMF: 1- Ion outflows
  
  • Maggiolo R.
  • Fontaine Dominique
  • Echim M.
  • Simon Wedlund C.
  • Zhang Y.
  , 2011, 33, pp.2120. The Cluster spacecraft reveal the presence of successive current sheets of opposite polarity above the polar caps during extended periods of northward IMF. At Cluster altitude (5-7 RE), the upward part of this current system consists of ion beams accelerated by quasi-static electric fields and associated with precipitating electrons. They are surrounded by low energy upflowing electron beams carrying a downward current. In this paper, we focus on Cluster observations of upflowing ion beams in the upward current region. These Polar Cap Ion Beams (PCIB) are accelerated by quasi-static electric fields. A recent statistical study shed new light on these structures. The PCIB have lifetimes that can exceed 20 minutes, they appear after northward turning of the IMF and disappear when it turns southward with a delay estimated to respectively ~2 hours and 20 minutes. Interestingly, about 40% of PCIB are detected together with isotropic plasma clouds located in the magnetospheric lobes. When present, the isotropic plasma population has a strong spatial correlation with PCIB suggesting that it is linked to the observed ion outflows. The temperature and pitch angle distribution of these isotropic ions show that they likely originate from the plasmasheet. The statistical properties of PCIB (size, orientation, IMF dependency...) are similar to those of optical polar cap arcs suggesting that both are different signatures of the same phenomenon. This is further confirmed by a case study combining Cluster in-situ data and TIMED optical observations. Using the high-altitude Cluster data as input to a magnetosphere-ionosphere coupling model we have been able to compute the UV emissions produced by the precipitating electrons associated with the PCIB. The modeled photo-emission is in good agreement with that of a polar cap arc observed by TIMED during the same time period. We'll discuss the new insight these observations give on the interaction between the magnetosphere and ionosphere during prolonged periods of northward IMF.
• Hybrid simulation of the interactions between Ganymede's magnetosphere and the jovian plasma
  
  • Allioux R.
  • Modolo Ronan
  • Louarn P.
  • Hess Sebastien
  • Leblanc François
  • Richer Emilie
  • Chanteur Gérard
  , 2011, 21, pp.id.SM21B-2009. Ganymede is the only magnetized moon in the solar system embedded in its large parent's planet magnetosphere. Its internal magnetic field interacts strongly with the Jovian magnetospheric plasma and makes unique this interaction. Thermal magnetospheric ions co-rotate at about 180km/s and are mainly composed of oxygen ions and protons. Few MHD models succeeded in describing accurately the global shape of the magnetosphere and reproduce most of the signatures observed by Galileo but they are unable to take in consideration high gyroradius effects or multiple ions dynamic. Therefore we developed a 3D parallel multi-species hybrid model based on a CAM-CL algorithm which has been largely used for other magnetized or unmagnetized body such as Mars, Titan or Mercury.
• Absolute Cl and Cl<SUB>2</SUB> densities in a Cl<SUB>2</SUB> ICP determined by TALIF with a new calibration method
  
  • Sirse Nishant
  • Azamoum Yasmina
  • Chabert Pascal
  • Booth Jean-Paul
  , 2011.
• Cluster Observations of Magnetopause Reconnection at Sub-Proton Scales
  
  • Retinò Alessandro
  • Vaivads A.
  • Sahraoui Fouad
  • Mozer F.
  • Zieger B.
  • Nakamura R.
  , 2011, pp.B2.
• Simulation Study of Solar Wind Interaction with Mercury's Magnetosphere
  
  • Richer Emilie
  • Modolo Ronan
  • Chanteur Gérard
  • Hess Sebastien
  • Mancini Marco
  • Leblanc François
  , 2011, 43, pp.abstract id.P43F-08. The three flybys of Mariner 10, the numerous terrestrial observations of Mercury's exosphere and the recent flybys of MESSENGER [1] 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 [2] and complex neutral environment made of several species : H, He, O, Na, K, Ca, and Mg have already been detected [3,4]. The small number of in situ observations and the fact that the Hermean magnetospheric activity is not observable from Earth make simulation studies of the Hermean environment a useful tool to understand the global interaction of the SW with Mercury. 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 observations during the first flyby of MESSENGER on January 2008 with a cone angle of ~45°. A neutral corona of atomic hydrogen is included in this model and is partly ionized by solar photons, electron impacts and charge exchange between SW ions and neutral H. Two electron fluids with different temperature are implemented to mimic the SW and ionospheric plasma. This model is an adapted version of the 3D parallel model for the Martian environment. 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 190×350×350 cells with a spatial resolution of Deltax~120km. Acknowledgements The authors are indebted to CNES (French space agency) for the funding of their modeling activity through its program Sun - Heliosphere - Magnetosphere and to ANR (French national agency for research) for supporting the HELIOSARES project. References [1] Anderson, B. J., Acuna, M. H., Korth, H., Purucker, M. E., Johnson, C. L., Slavin, J. A., Solomon, S. C. and McNutt, R. L.: The Structure of Mercury's Magnetic Field from MESSENGER's First Flyby, Science, Vol. 321, pp. 82-, 2008 [2] Leblanc, F., Doressoundiram, A., Schneider, N., Mangano, V., López Ariste, A., Lemen, C., Gelly, B., Barbieri, C., remonese, G. : High latitude peaks in Mercury's sodium exosphere: Spectral signature using THEMIS solar telescope, Geophysical Research Letters, Vol. 35, L18204, 2008 [3] Leblanc, F. and Doressoundiram, A. : Mercury exosphere. II. The sodium/potassium ratio, Icarus, Vol. 211, pp. 10-20, 2011 [4] Potter, A. and Morgan, T. : Discovery of sodium in the atmosphere of Mercury, Science, Vol. 229, pp. 651-653, 1985
• A new 3D parallel multi-species hybrid model for Solar Wind - Mars interaction
  
  • Hess Sebastien
  • Modolo Ronan
  • Mancini Marco
  • Allioux R.
  • Richer Emilie
  • Leblanc François
  • Chaufray Jean-Yves
  • Yagi Manabu
  • Chanteur Gérard
  , 2011, 13, pp.id.SA13A-1870. Due to the absence of strong intrinsic magnetic field, the Martian atmosphere/exosphere is directly in contact with the Solar Wind, exchanging part of its momentum and energy. This coupling occurs via ionization processes and contributes to the erosion of the neutral environment of the planet. Several space missions (past, active and future), such as Phobos-2, MGS, Mars-Express and soon MAVEN, are dedicated to reveal the Martian neutral and ionized environment properties. Many in situ observations are available and characterize the plasma (and neutral) environment in the near vicinity of the spacecraft but these observations are highly localized in space and time. With a single spacecraft it is difficult to separate spatial from temporal structures and we often resort to global simulation to set back the observation in a global context. In the frame of the HELIOSARES project (granted by the French National Agency), we have parallelized our previous hybrid model. This study presents the first simulation results with an improved 75 km spatial resolution from a 3-dimensional parallel multi-species hybrid model of the Martian interaction with the Solar Wind.
• Energetic Electron Acceleration at Reconnection Jet Fronts in the Magnetotail
  
  • Retinò Alessandro
  • Vaivads A.
  • Zieger B.
  • Nakamura R.
  • Kasahara S.
  , 2011, 13, pp.2101. Magnetic reconnection plays a key role for particle acceleration in many astrophysical plasmas. Important examples are reconnection during planetary substorms and solar flares. A number of recent numerical simulations as well as of in situ observations in the magnetotail indicate that strong acceleration can occur at reconnection jet fronts, separating jetting from ambient plasma, and in the jet braking region, where jets eventually stop/dissipate. Yet the details of the acceleration mechanisms are not completely understood. Here we present ESA/ Cluster observations of energetic electron (>30 keV) acceleration at the fronts of earthward-directed reconnection jets in the magnetotail. We find that jet fronts are highly structured on the spatial scale of a few ion gyroradii suggesting a filamentation of the reconnection jet possibly due to interchange instability. Strong electron energization is associated to such filamented jet fronts. Electrons are typically energized in the direction perpendicular to the magnetic field indicating betatron acceleration. Waves in the whistler frequency range are associated to the strongest perpendicular flux increases. Yet the observed electron distributions and waves indicate that more complicated acceleration mechanisms can also occur at localized structures within the fronts.
• Field-aligned acceleration above the polar caps during prolonged periods of Northward IMF: 2. Polar electron precipitation
  
  • Fontaine Dominique
  • Maggiolo R.
  , 2011, 33, pp.2121. The Cluster spacecraft reveal the presence of successive current sheets of opposite polarity above the polar caps during extended periods of northward IMF. At Cluster altitude (5-7 RE), the upward part of this current system consists of ion beams accelerated by quasi-static electric fields and associated with precipitating electrons. They are surrounded by low energy upflowing electron beams carrying a downward current. In this paper, we focus on the precipitating electrons systematically observed by Cluster during the events of ionospheric ion outflows above the polar cap and contributing to the upward currents. Energetic events are occasionally observed, but usually the precipitating electrons are accelerated at weak energies, around 100 - 300 eV. This electron acceleration is interpreted similarly to the simultaneous ion acceleration as the effect of an electrostatic electric field along magnetic field lines. This implies the existence of a potential structure located above CLUSTER altitude, i.e. typically above 5-7 RE, which accelerates the magnetospheric electrons towards the polar cap , in addition of the low-altitude potential structure responsible for the ion outflows escaping the ionosphere. We present statistics on the characteristics of these precipitating electron structures, only observed during time periods of northward IMF. We discuss the source regions and the mechanisms possibly at their origin.
• Measurements of density fluctuations in magnetic confined plasmas
  
  • Vermare Laure
  , 2011.
• Study of the EEDF and electronic temperature through various magnetic field barriers
  
  • Bredin Jérôme
  • Aanesland Ane
  • Chabert Pascal
  • Godyak Valery
  , 2011.
• A global model of the self-pulsing regime of micro-hollow cathode discharges
  
  • Lazzaroni Claudia
  • Chabert Pascal
  , 2011.
• Spectroscopic Analysis of First Experiments of Al Planar Foils and Single Planar Wire Arrays on Zebra at UNR
  
  • Zunino H. A.
  • Weller Michael E.
  • Stafford A.
  • Safronova Alla S.
  • Kantsyrev V. I.
  • Chuvatin Alexandre S.
  • Shrestha Ishor
  • Osborne Glenn C.
  • Shlyaptseva V. V.
  • Keim S. F.
  , 2011, 56 (16), pp.PP9.00108.
• Experimental Comparison of Radiative Characteristics and Implosion Dynamics of Planar Foils and Single Planar Wire Arrays in Current Region 0.9-1.6 MA on the UNR Zebra generator
  
  • Kantsyrev Viktor L.
  • Chuvatin Alexandre S.
  • Rudakov Leonid I.
  • Safronova Alla S.
  • Esaulov A. A.
  • Osborne Glenn C.
  • Shrestha Ishor
  • Shlyaptseva V. V.
  • Zunino H. A.
  • Weller Michael E.
  • Stafford A.
  • Keim S. F.
  , 2011, 56 (16), pp.GO6.00007.
• Photo-fusion reactions in a new compact device for ELI
  
  • Moustaizis Stavros
  • Auvray Philippe
  • Hora Heinrich
  • Lalousis P.
  • Larour Jean
  • Mourou Gérard
  , 2011, 1462, pp.191-194. In the last few years significant progress on technological, experimental and numerical studies on fusion process in high density and high temperature plasmas produced by a high intensity laser pulse interaction with clusters in a high external applied magnetic field, enable us to propose a compact photo-fusion magnetic device for high neutron production. For the purpose of the project a pulsed magnetic field driver with values up to 110 Tesla has been developed which allows increasing the trapping time of the high density plasma in the device and improving the neutron yield. Numerical simulations show that the proposed device is capable of producing up to 109-1010 neutrons per laser shot with an external magnetic field of 150 Tesla. The proposed device can be used for experiments and numerical code validation concerning different conventional and (or) exotic fusion fuels. oral communication
• Alternate acceleration of positive and negative ions for space propulsion applications
  
  • Aanesland Ane
  , 2011.
• Analysis of Radiation from Implosions of Stainless Steel Wire Arrays on Zebra and Comparison with Laser Plasma Experiments on Leopard at UNR
  
  • Safronova Alla S.
  • Kantsyrev Viktor L.
  • Shrestha Ishor
  • Shlyaptseva V. V.
  • Weller Michael E.
  • Osborne Glenn C.
  • Williamson Kenneth M.
  • Stafford A.
  • Legalloudec N.
  • Paudel Y.
  • Coverdale C.
  • Chuvatin Alexandre S.
  , 2011, 56 (16), pp.GO6.00003.
• Geomagnetism during solar cycle 23 : characteristics
  
  • Amory-Mazaudier Christine
  • Zerbo J.-L.
  • Ouattara Frédéric
  , 2011.
• DEPOSITION OF THIN FILM OF SILICON MICROCRISTALLINE BY RADIO FREQUENCY VOLTAGE WAVEFORM TAILORING
  
  • Pouliquen S.
  • Delattre Pierre-Alexandre
  • Johnson E.V.
  • Booth Jean-Paul
  , 2011.
• Atomic Chlorine absolute densities and surface recombination coefficients in inductively coupled plasmas in Cl<SUB>2</SUB>
  
  • Booth Jean-Paul
  • Sirse Nishant
  • Azamoum Yasmina
  • Chabert Pascal
  , 2011.
• Plasma diffusion in self-consistent fluctuations
  
  • Smets Roch
  • Belmont Gérard
  • Aunai Nicolas
  • Rezeau Laurence
  Physics of Plasmas, American Institute of Physics, 2011, 18, pp.102310. The problem of particle diffusion in position space, as a consequence of electromagnetic fluctuations is addressed. Numerical results obtained with a self-consistent hybrid code are presented, and a method to calculate diffusion coefficient in the direction perpendicular to the mean magnetic field is proposed. The diffusion is estimated for two different types of fluctuations. The first type (resulting from an agyrotropic initial setting) is stationary, wide band white noise, and associated to Gaussian probability distribution function for the magnetic fluctuations. The second type (resulting from a Kelvin-Helmholtz instability) is non-stationary, with a power-law spectrum, and a non-Gaussian probability distribution function. The results of the study allow revisiting the question of loading particles of solar wind origin in the Earth magnetosphere. (10.1063/1.3647558)
  DOI : 10.1063/1.3647558