Publications

2011

• Numerical analysis of electronegative plasma in the extraction region of negative hydrogen ion sources
  
  • Kuppel S.
  • Matsushita D.
  • Hatayama A.
  • Bacal M.
  Journal of Applied Physics, American Institute of Physics, 2011, 109 (1), pp.013305. This numerical study focuses on the physical mechanisms involved in the extraction of volume-produced H− ions from a steady state laboratory negative hydrogen ion source with one opening in the plasma electrode (PE) on which a dc-bias voltage is applied. A weak magnetic field is applied in the source plasma transversely to the extracted beam. The goal is to highlight the combined effects of the weak magnetic field and the PE bias voltage (upon the extraction process of H− ions and electrons). To do so, we focus on the behavior of electrons and volume-produced negative ions within a two-dimensional model using the particle-in-cell method. No collision processes are taken into account, except for electron diffusion across the magnetic field using a simple random-walk model at each time step of the simulation. The results show first that applying the magnetic field (without PE bias) enhances H− ion extraction, while it drastically decreases the extracted electron current. Secondly, the extracted H− ion current has a maximum when the PE bias is equal to the plasma potential, while the extracted electron current is significantly reduced by applying the PE bias. The underlying mechanism leading to the above results is the gradual opening by the PE bias of the equipotential lines towards the parts of the extraction region facing the PE. The shape of these lines is due originally to the electron trapping by the magnetic field. (10.1063/1.3530454)
  DOI : 10.1063/1.3530454
• Kelvin-Helmholtz waves under southward interplanetary magnetic field
  
  • Hwang K.-J.
  • Kuznetsova M. M.
  • Sahraoui Fouad
  • Goldstein M. L.
  • Lee E.
  • Parks G. K.
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2011, 116, pp.8210. The Kelvin-Helmholtz waves have been observed along the Earth's low-latitude magnetopause and have been suggested to play a certain role in the entry of solar wind plasma into Earth's magnetosphere. In situ observations of the KH waves (KHW) and, in particular, a nonlinear stage of the KH instability, i.e., rolled-up KH vortices (KHVs), have been reported to occur preferentially for northward interplanetary magnetic field (IMF). Using Cluster data, we present the first in situ observation of nonlinearly developed KHW during southward IMF. The analysis reveals that there is a mixture of less-developed and more-developed KHW that shows inconsistent variations in scale size and the magnetic perturbations in the context of the expected evolution of KH structures. A coherence analysis implies that the observed KHW under southward IMF appear to be irregular and intermittent. These irregular and turbulent characteristics are more noticeable than previously reported KHW events that have been detected preferentially during northward IMF. This suggests that under southward IMF KHVs become easily irregular and temporally intermittent, which might explain the preferential in situ detection of KHVs when the IMF is northward. MHD simulation of the present event shows that during southward IMF dynamically active subsolar environments can cause KHV that evolve with considerable intermittency. The MHD simulations appear to reproduce well the qualitative features of the Cluster observations. (10.1029/2011JA016596)
  DOI : 10.1029/2011JA016596
• Three-dimensional spatial structures of solar wind turbulence from 10 000-km to 100-km scales
  
  • Narita Y.
  • Glassmeier K.-H.
  • Goldstein M. L.
  • Motschmann U.
  • Sahraoui Fouad
  Annales Geophysicae, European Geosciences Union, 2011, 29, pp.1731-1738. Using the four Cluster spacecraft, we have determined the three-dimensional wave-vector spectra of fluctuating magnetic fields in the solar wind. Three different solar wind intervals of Cluster data are investigated for this purpose, representing three different spatial scales: 10 000 km, 1000 km, and 100 km. The spectra are determined using the wave telescope technique (k-filtering technique) without assuming the validity of Taylor's frozen-in-flow hypothesis nor are any assumptions made as to the symmetry properties of the fluctuations. We find that the spectra are anisotropic on all the three scales and the power is extended primarily in the directions perpendicular to the mean magnetic field, as might be expected of two-dimensional turbulence, however, the analyzed fluctuations are not axisymmetric. The lack of axisymmetry invalidates some earlier techniques using single spacecraft observations that were used to estimate the percentage of magnetic energy residing in quasi-two-dimensional power. However, the dominance of two-dimensional turbulence is consistent with the relatively long mean free paths of cosmic rays in observed in the heliosphere. On the other hand, the spectra also exhibit secondary extended structures oblique from the mean magnetic field direction. We discuss possible origins of anisotropy and asymmetry of solar wind turbulence spectra. (10.5194/angeo-29-1731-2011)
  DOI : 10.5194/angeo-29-1731-2011
• On the dispersion features of whistler waves in almost pure ion plasmas
  
  • Lundin B. V.
  • Krafft C.
  Physics of Plasmas, American Institute of Physics, 2011, 18, pp.102114. It is shown that in a multi-ion plasma of moderate density enriched by a large amount of negatively charged ions and/or heavy particulates, the lower cutoff frequencies of the electron whistler and the Z-mode (extraordinary) waves tend to each other, approaching the ion plasma frequency omegapi. The evolution of the dispersion curves omega(k, theta) of both wave modes is studied as a function of the relative electron density, beginning from the case of a moderate density plasma with comparable values of electron gyro- and plasma frequencies and omegapi essentially exceeding the ions' gyrofrequencies. When the fraction of free electrons is very small the transparency frequency domain of the electron whistler mode becomes very narrow, being located in the vicinity of omegapi. If the negatively charged ions have the smallest specific charges among other ion species then, under similar conditions, the so-called crossover effect and the accompanying polarization sense reverse can occur at frequencies essentially greater than the ions' gyrofrequencies. The revealed effects are characteristic of plasmas with excess of electronegative gas molecules or dust particulates highly adhesive to electrons, i.e., almost pure ion plasmas and/or pair-ion plasmas with extra small fractions of free electrons. Moreover, it is found that the vanishingly small electron fraction providing the same value of the electron whistler ion cutoff frequency normalized to the ion plasma frequency is essentially less for pair fullerene C<SUB>60</SUB><SUP> /-</SUP> than for pair hydrogen H /- plasmas. The technique to determine omegapi using the evolution of the whistler wave magnetic field polarization ellipse is also described. (10.1063/1.3650075)
  DOI : 10.1063/1.3650075
• Energy budgets in collisionless magnetic reconnection: Ion heating and bulk acceleration
  
  • Aunai Nicolas
  • Belmont Gérard
  • Smets Roch
  Physics of Plasmas, American Institute of Physics, 2011, 18, pp.122901. This paper investigates the energy transfer in the process of collisionless antiparallel magnetic reconnection. Using two-dimensional hybrid simulations, we measure the increase of the bulk and thermal kinetic energies and compare it to the loss of magnetic energy through a contour surrounding the ion decoupling region. It is shown, for both symmetric and asymmetric configurations, that the loss of magnetic energy is not equally partitioned between heating and acceleration. The heating is found to be dominant and the partition ratio depends on the asymptotic parameters, and future investigations will be needed to understand this dependence. (10.1063/1.3664320)
  DOI : 10.1063/1.3664320
• Landau and Non-Landau Linear Damping: Physics of the Dissipation
  
  • Belmont Gérard
  • Chust Thomas
  • Mottez Fabrice
  • Hess S.
  Transport Theory and Statistical Physics, Taylor & Francis, 2011, 40 (6-7), pp.419-424. The linear Landau effect is revisited by the means of numerical simulations and analytical calculations. The existence of non-Landau solutions to the Vlasov-Poisson system is emphasized and the consistency of these solutions with respect to the arguments based on energy is investigated. The present article briefly summarizes the content of two articles already published on the subject and introduces a discussion based on the exchanges that occurred at Marseille during the Vlasovia meeting. (10.1080/00411450.2011.651055)
  DOI : 10.1080/00411450.2011.651055
• Discharge resistance and power dissipation in the self-pulsing regime of micro-hollow cathode discharges
  
  • Lazzaroni Claudia
  • Chabert Pascal
  Plasma Sources Science and Technology, IOP Publishing, 2011, 20, pp.055004. Micro-hollow cathode discharges (MHCDs), driven by a dc voltage source, may operate in a self-pulsing regime during which the voltage and the current across the discharge are pulsed with a frequency of several tens of kilohertz. A model for the self-pulsing regime of MHCDs is proposed based on an equivalent electrical circuit of the whole device. The discharge itself is modeled by a non-linear resistance in series with an inductance, and it is placed in parallel with the capacitance of the electrodedielectricelectrode sandwich hosting the discharge micro-hole. The capacitance of the coaxial cable used to feed the device is also included. It is shown that a detailed comparison between theory and experiments allows the discharge non-linear resistance to be accurately determined. When the discharge current is maximum, this resistance is about 2500&#8201;&#937; at 50&#8201;Torr and decreases to about 750&#8201;&#937; at 150&#8201;Torr. The absorbed power is calculated throughout the self-pulsing cycle and may be above 100&#8201;W at the current peak, while the time-averaged power remains a fraction of a Watt. (10.1088/0963-0252/20/5/055004)
  DOI : 10.1088/0963-0252/20/5/055004
• On plasma- and UV-induced VOC oxidation on TiO<SUB>2</SUB> surface pre-treated by plasma exposure monitored by QCLAS
  
  • Marinov Daniil
  • Lopatik D.
  • Guaitella Olivier
  • Hübner M.
  • Rousseau Antoine
  • Roepcke J.
  , 2011.
• Magnetic reconnection in the Jovian tail: X-line evolution and consequent plasma sheet structures
  
  • Kasahara S.
  • Kronberg E. A.
  • Krupp N.
  • Kimura T.
  • Tao C.
  • Badman S. V.
  • Retinò Alessandro
  • Fujimoto M.
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2011, 116, pp.11219. Magnetic reconnection in planetary magnetospheres plays important roles in energy and mass transfer in the steady state, and also possibly in transient large-scale disturbances. In this paper we report observations of a reconnection event in the Jovian magnetotail by the Galileo spacecraft on 17 June 1997. In addition to the tailward retreat of a main X-line, signatures of recurrent X-line formations are found by close examination of energetic particle anisotropies. Furthermore, detailed analyses of multi-instrumental data for this period provide various spatiotemporal features in the plasma sheet. A significant density decrease was detected in the central plasma sheet, indicative of the transition to lobe (open field line) reconnection from plasma sheet (closed field line) reconnection. When Galileo vertically swept through the plasma sheet, a velocity layer structure was observed. We also analyze a strong southward magnetic field which is similar to dipolarization fronts observed in the terrestrial magnetotail: the ion flow (450 km s<SUP>-1</SUP>) was observed behind the magnetic front, whose thickness of 10000-20000 km was of the order of ion inertial length. The electron anisotropy in this period suggests an anomalously high-speed electron jet, implying ion-electron decoupling behind the magnetic front. Particle energization was also seen associated with these structures. These observations suggest that X-line evolution and consequent plasma sheet structures are similar to those in the terrestrial magnetosphere, whereas their generality in the Jovian magnetosphere and influence on the magnetospheric/ionospheric dynamics including transient auroral events need to be further investigated with more events. (10.1029/2011JA016892)
  DOI : 10.1029/2011JA016892
• On plasma rotation with toroidal magnetic field ripple and no external momentum input
  
  • Fenzi C.
  • Garbet X.
  • Trier Elisée
  • Hennequin Pascale
  • Bourdelle C.
  • Aniel Thierry
  • Colledani G.
  • Devynck P.
  • Gil C.
  • Gürcan Özgür D.
  • Manenc L.
  • Schneider M.
  • Segui J.-L.
  • Tore Supra Team
  Nuclear Fusion, IOP Publishing, 2011, 51, pp.103038. Ripple-induced thermal loss effect on plasma rotation is investigated in a set of Ohmic L-mode plasmas performed in Tore Supra, and comparisons with neoclassical predictions including ripple are performed. Adjusting the size of the plasma, the ripple amplitude has been varied from 0.5% to 5.5% at the plasma boundary, keeping the edge safety factor constant. The toroidal flow dynamics is understood as being likely dominated by turbulence transport driven processes at low ripple amplitude, while the ripple-induced toroidal friction becomes dominant at high ripple. In the latter case, the velocity tends remarkably towards the neoclassical prediction (counter-current rotation). The radial electric field is not affected by the ripple variation and remains well described by its neoclassical prediction. Finally, the poloidal velocity is of the order of the neoclassical prediction at high ripple amplitude, but significantly departs from it at low ripple. (10.1088/0029-5515/51/10/103038)
  DOI : 10.1088/0029-5515/51/10/103038
• Modeling the superstorm in November 2003
  
  • Fok M.-C. H.
  • Moore T. E.
  • Slinker Steve P.
  • Fedder Joel A.
  • Delcourt Dominique C.
  • Nosé Masahito
  • Chen Sheng-Hsien
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2011, 116. The superstorm on 20-21 November 2003 was the largest geomagnetic storm in solar cycle 23 as measured by Dst, which attained a minimum value of -422 nT. We have simulated this storm to understand how particles originating from the solar wind and ionosphere get access to the magnetosphere and how the subsequent transport and energization processes contribute to the buildup of the ring current. The global electromagnetic configuration and the solar wind H<SUP> </SUP> distribution are specified by the Lyon-Fedder-Mobarry (LFM) magnetohydrodynamics model. The outflow of H<SUP> </SUP> and O<SUP> </SUP> ions from the ionosphere are also considered. Their trajectories in the magnetosphere are followed by a test-particle code. The particle distributions at the inner plasma sheet established by the LFM model and test-particle calculations are then used as boundary conditions for a ring current model. Our simulations reproduce the rapid decrease of Dst during the storm main phase and the fast initial phase of recovery. Shielding in the inner magnetosphere is established at early main phase. This shielding field lasts several hours and then breaks down at late main phase. At the peak of the storm, strong penetration of ions earthward to L shell of 1.5 is revealed in the simulation. It is surprising that O<SUP> </SUP> is significant but not the dominant species in the ring current in our calculation for this major storm. It is very likely that substorm effects are not well represented in the models and O<SUP> </SUP> energization is underestimated. Ring current simulation with O<SUP> </SUP> energy density at the boundary set comparable to Geotail observations produces excellent agreement with the observed symH. As expected in superstorms, ring current O<SUP> </SUP> is the dominant species over H<SUP> </SUP> during the main to midrecovery phase of the storm. (10.1029/2010JA015720)
  DOI : 10.1029/2010JA015720
• Proton acceleration in antiparallel collisionless magnetic reconnection: Kinetic mechanisms behind the fluid dynamics
  
  • Aunai Nicolas
  • Belmont Gérard
  • Smets Roch
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2011, 116, pp.9232. This paper investigates the proton kinetic mechanisms leading to the formation of plasma jets in antiparallel magnetic reconnection. In particular, the interaction of the protons with the Hall electric field in the proton non-ideal region is discussed. The study, based on a two-dimensional hybrid simulation, details the important role of the proton pressure force in the acceleration process and its role in maintaining open and steady the proton outflow channel. When no fluid closure is assumed, it is found that this force arises from a strong anisotropy in velocity space which comes from kinetic effect. By analyzing the distribution functions and the individual particle dynamics, it is shown that the mixing of protons bouncing in a divergent electrostatic potential well associated to the Hall effect statistically couples the two in-plane velocity components of the particles. This coupling results, from the macroscopic point of view, in off-diagonal components of the pressure tensor. (10.1029/2011JA016688)
  DOI : 10.1029/2011JA016688
• The proton pressure tensor as a new proxy of the proton decoupling region in collisionless magnetic reconnection
  
  • Aunai Nicolas
  • Retinò Alessandro
  • Belmont Gérard
  • Smets Roch
  • Lavraud B.
  • Vaivads A.
  Annales Geophysicae, European Geosciences Union, 2011, 29, pp.1571-1579. Cluster data is analyzed to test the proton pressure tensor variations as a proxy of the proton decoupling region in collisionless magnetic reconnection. The Hall electric potential well created in the proton decoupling region results in bounce trajectories of the protons which appears as a characteristic variation of one of the in-plane off-diagonal components of the proton pressure tensor in this region. The event studied in this paper is found to be consistent with classical Hall field signatures with a possible 20% guide field. Moreover, correlations between this pressure tensor component, magnetic field and bulk flow are proposed and validated, together with the expected counterstreaming proton distribution functions. (10.5194/angeo-29-1571-2011)
  DOI : 10.5194/angeo-29-1571-2011
• Multi-spacecraft investigation of space turbulence: lessons from Cluster and input to the Cross- Scale mission
  
  • Sahraoui Fouad
  • Goldstein M.L.
  • Belmont Gérard
  • Roux A.
  • Rezeau Laurence
  • Canu Patrick
  • Robert Patrick
  • Cornilleau-Wehrlin Nicole
  • Le Contel Olivier
  • Dudok de Wit Thierry
  • Pinçon Jean-Louis
  • Kiyani K.
  Planetary and Space Science, Elsevier, 2011, 59 (7), pp.Pages 585-591. Investigating space plasma turbulence from single-point measurements is known to be characterized by unavoidable ambiguities in disentangling temporal and spatial variations. Solving this problem has been one of the major goals of the Cluster mission. For that purpose multipoint measurements techniques, such as the $k$-filtering, have been developed. Such techniques combine several time series recorded simultaneously at different points in space to estimate the corresponding energy density in the wavenumber space. Here we apply the technique to both simulated and Cluster magnetometer data in the solar wind (SW) and investigate the errors and limitations that arise due to the separation of the spacecraft and the quality of the tetrahedral configuration. Specifically, we provide an estimation of the minimum and maximum scales that can be accurately measured given a specific distance between the satellites and show the importance of the geometry of the tetrahedron and the relationship of that geometry to spatial aliasing. We also present recent results on characterizing small scale SW turbulence and provide scientific arguments supporting the need of new magnetometers having better sensitivity than the existing ones. Throughout the paper we emphasize technical challenges and their solutions that can be considered for a better preparation of the Cross- Scale mission. (10.1016/j.pss.2010.06.001)
  DOI : 10.1016/j.pss.2010.06.001
• Vibrational relaxation of N<SUB>2</SUB> studied by IR titration with time-resolved Qantum Cascade Laser diagnostics
  
  • Marinov Daniil
  • Lopatik D.
  • Guaitella Olivier
  • Roepcke J.
  • Rousseau Antoine
  , 2011.
• Predator prey oscillations in a simple cascade model of drift wave turbulence
  
  • Berionni Vincent
  • Gürcan Özgür D.
  Physics of Plasmas, American Institute of Physics, 2011, 18, pp.112301. A reduced three shell limit of a simple cascade model of drift wave turbulence, which emphasizes nonlocal interactions with a large scale mode, is considered. It is shown to describe both the well known predator prey dynamics between the drift waves and zonal flows and to reduce to the standard three wave interaction equations. Here, this model is considered as a dynamical system whose characteristics are investigated. The analytical solutions for the purely nonlinear limit are given in terms of the Jacobi elliptic functions. An approximate analytical solution involving Jacobi elliptic functions and exponential growth is computed using scale separation for the case of unstable solutions that are observed when the energy injection rate is high. The fixed points of the system are determined, and the behavior around these fixed points is studied. The system is shown to display periodic solutions corresponding to limit cycle oscillations, apparently chaotic phase space orbits, as well as unstable solutions that grow slowly while oscillating rapidly. The period doubling route to transition to chaos is examined. (10.1063/1.3656953)
  DOI : 10.1063/1.3656953
• Stochastic treatment of finite-N effects in mean-field systems and its application to the lifetimes of coherent structures
  
  • Ettoumi Wahb
  • Firpo Marie-Christine
  Physical Review E, American Physical Society (APS), 2011, 84, pp.030103(R). A stochastic treatment yielding to the derivation of a general Fokker-Planck equation is presented to model the slow convergence toward equilibrium of mean-field systems due to finite-N effects. The thermalization process involves notably the disintegration of coherent structures that may sustain out-of-equilibrium quasistationary states. The time evolution of the fraction of particles remaining close to a mean-field potential trough is analytically computed. This indicator enables to estimate the lifetime of coherent structures and thermalization time scale in mean-field systems. (10.1103/PhysRevE.84.030103)
  DOI : 10.1103/PhysRevE.84.030103
• Collisionality scaling in Tore Supra: detailed energy confinement analysis, turbulence measurements and gyrokinetic modelling
  
  • Bourdelle C.
  • Gerbaud T.
  • Vermare Laure
  • Casati A.
  • Aniel Thierry
  • Artaud J.F.
  • Basiuk Vincent
  • Bucalossi J.
  • Clairet F.
  • Corre Y.
  • Devynck P.
  • Falchetto G.
  • Fenzi C.
  • Garbet X.
  • Guirlet R.
  • Gürcan Özgür D.
  • Heuraux S.
  • Hennequin Pascale
  • Hoang G.T.
  • Imbeaux Frédéric
  • Manenc L.
  • Monier-Garbet P.
  • Moreau P.
  • Sabot R.
  • Segui J.-L.
  • Sirinelli A.
  • Villegas D.
  • Tore Supra Team
  Nuclear Fusion, IOP Publishing, 2011, 51, pp.063037. This paper presents the first observation of geodesic acoustic modes (GAMs) on Tore Supra plasmas. Using the Doppler backscattering system, the oscillations of the plasma flow velocity, localized between r/a = 0.85 and r/a = 0.95, and with a frequency, typically around 10 kHz, have been observed at the plasma edge in numerous discharges. When the additional heating power is varied, the frequency is found to scale with Cs/R. The MUltiple SIgnal Classification (MUSIC) algorithm is employed to access the temporal evolution of the perpendicular velocity of density fluctuations. The method is presented in some detail, and is validated and compared against standard methods, such as the conventional fast Fourier transform method, using a synthetic signal. It stands out as a powerful data analysis method to follow the Doppler frequency with a high temporal resolution, which is important in order to extract the dynamics of GAMs. (10.1088/0029-5515/51/6/063037)
  DOI : 10.1088/0029-5515/51/6/063037
• Wavenumber spectrum of micro-turbulence in tokamak plasmas / Spectre en nombre d'onde de la micro-turbulence dans les plasmas de tokamak
  
  • Vermare Laure
  • Gürcan Özgür D.
  • Hennequin Pascale
  • Honoré Cyrille
  • Garbet X.
  • Giacalone J-C.
  • Sabot R.
  • Clairet F.
  • Tore Supra Team
  Comptes Rendus. Physique, Académie des sciences (Paris), 2011, 12 (2), pp.115 - 122. A better understanding of turbulent transport in a tokamak plasma requires precise comparisons between experimental observation and theoretical prediction of micro-turbulence characteristics. The repartition of fluctuation energy over different spatial scales, which contains detailed information about the character of underlying instabilities and the mechanisms involved in energy transfer between different scales, is one of the few quantities allowing a high detail comparison. The present article reports the investigation performed on the Tore Supra tokamak on the wavenumber spectrum of micro-turbulence using Doppler backscattering. The theoretical approach consists of the derivation of spectral models that include interactions between fluctuations and large scale flow structures. Une meilleure compréhension du transport turbulent dans les plasmas de tokamak exige des comparaisons précises entre les observations expérimentales et les prédictions théoriques des caractéristiques de la micro-turbulence. La répartition de l&#700;énergie des fluctuations sur les différentes échelles spatiales, qui contient des informations sur le type instabilités sous-jacentes et sur les mécanismes de transfert d&#700;énergie entre échelles spatiales, est l&#700;une des rares quantités permettant une comparaison de niveau élevé. Cet article présente le travail mené sur le tokamak Tore Supra sur l&#700;étude du spectre en nombre d&#700;onde de la micro-turbulence mesuré par rétro-diffusion Doppler. L&#700;approche théorique consiste en la dérivation de modéles spectraux qui inclut les interactions entre les fluctuations et les structures d&#700;écoulement de grandes échelles. (10.1016/j.crhy.2010.11.003)
  DOI : 10.1016/j.crhy.2010.11.003
• Whistler eigenmodes of magnetic flux tubes in a magnetoplasma
  
  • Kudrin A. V.
  • Bakharev P. V.
  • Zaboronkova T. M.
  • Krafft C.
  Plasma Physics and Controlled Fusion, IOP Publishing, 2011, 53, pp.065005. Guided propagation of whistler waves along cylindrical non-uniformities of a dc magnetic field is studied within the framework of a full-wave approach. Conditions are revealed under which such guiding structures, commonly known as magnetic flux tubes, can support volume and surface eigenmodes in the whistler range. The dispersion properties and field structures of whistler eigenmodes guided by flux tubes with an enhanced magnetic field are calculated and analysed for plasma parameters typical of laboratory experiments. The results obtained are useful in understanding the basic features of whistler wave guidance by magnetic flux tubes and can be applied to interpreting the data of the relevant experiments. (10.1088/0741-3335/53/6/065005)
  DOI : 10.1088/0741-3335/53/6/065005
• Alfvén : Magnetosphere -Ionosphere Connection Explorers
  
  • Berthomier Matthieu
  • Fazakerlay, N. A.
  • Forsyth C.
  • Pottelette Raymond
  • Alexandrova Olga
  • Anastasiadis A.
  • Aruliah A.
  • Blelly Pierre-Louis
  • Briand Carine
  • Bruno R.
  • Canu Patrick
  • Cecconi Baptiste
  • Chust Thomas
  • Daglis I.
  • Davie J.
  • Dunlop M.
  • Fontaine Dominique
  • Génot Vincent
  • Gustavsson B.
  • Haerendel G.
  • Hamrin M.
  • Hapgood M.
  • Hess S.
  • Kataria D.
  • Kauristie K.
  • Kemble S.
  • Khotyaintsev Y.
  • Koskinen H.
  • Lamy Laurent
  • Lanchester B.
  • Louarn P.
  • Lucek E.
  • Lundin R.
  • Maksimovic M.
  • Manninen J.
  • Marchaudon Aurélie
  • Marghitu O.
  • Marklund G.
  • Milan S.
  • Moen J.
  • Mottez Fabrice
  • Nilsson Hans
  • Parrot Michel
  • Ostgaard N.
  • J. Owen C.
  • Pedersen A.
  • Perry C.
  • Pinçon Jean-Louis
  • Pitout Frederic
  • Pulkkinen T.
  • J. Rae I.
  • Rezeau Laurence
  • Roux A.
  • Sandahl I.
  • Sandberg I.
  • Turunen E.
  • Vogt J.
  • Walsh A.
  • E. J. Watt C.
  • A. Wild J.
  • Yamauchi M.
  • Zarka Philippe
  • Zouganelis I.
  Experimental Astronomy, Springer Link, 2011, pp.1. The Alfvén concept is designed specifically to take the next step in studying the aurora, by making the crucial high-time resolution, multi-scale measurements in the AAR, needed to address the key science questions of auroral plasma physics. The new knowledge that the mission will produce will find application in studies of the Sun, the processes that accelerate the solar wind and that produce aurora on other planets. (10.1007/s10686-011-9273-y)
  DOI : 10.1007/s10686-011-9273-y
• Experimental and modeling analysis of fast ionization wave discharge propagation in a rectangular geometry
  
  • Takashima K.
  • Adamovich I.V.
  • Xiong Z.
  • Kushner M.J.
  • Starikovskaia Svetlana
  • Czarnetzki U.
  • Luggenhölscher D.
  Physics of Plasmas, American Institute of Physics, 2011, 18, pp.083505. Fast ionization wave (FIW), nanosecond pulse discharge propagation in nitrogen and helium in a rectangular geometry channel/waveguide is studied experimentally using calibrated capacitive probe measurements. The repetitive nanosecond pulse discharge in the channel was generated using a custom designed pulsed plasma generator (peak voltage 1040 kV, pulse duration 30100 ns, and voltage rise time &#8764;1 kV/ns), generating a sequence of alternating polarity high-voltage pulses at a pulse repetition rate of 20 Hz. Both negative polarity and positive polarity ionization waves have been studied. Ionization wave speed, as well as time-resolved potential distributions and axial electric field distributions in the propagating discharge are inferred from the capacitive probe data. ICCD images show that at the present conditions the FIW discharge in helium is diffuse and volume-filling, while in nitrogen the discharge propagates along the walls of the channel. FIW discharge propagation has been analyzed numerically using quasi-one-dimensional and two-dimensional kinetic models in a hydrodynamic (drift-diffusion), local ionization approximation. The wave speed and the electric field distribution in the wave front predicted by the model are in good agreement with the experimental results. A self-similar analytic solution of the fast ionization wave propagation equations has also been obtained. The analytic model of the FIW discharge predicts key ionization wave parameters, such as wave speed, peak electric field in the front, potential difference across the wave, and electron density as functions of the waveform on the high voltage electrode, in good agreement with the numerical calculations and the experimental results. (10.1063/1.3619810)
  DOI : 10.1063/1.3619810
• Emission and propagation of Saturn kilometric radiation: Magnetoionic modes, beaming pattern, and polarization state
  
  • Lamy L.
  • Cecconi B.
  • Zarka P.
  • Canu Patrick
  • Schippers P.
  • Kurth W. S.
  • Mutel R. L.
  • Gurnett D. A.
  • Menietti D.
  • Louarn P.
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2011, 116, pp.4212. The Cassini mission crossed the source region of the Saturn kilometric radiation (SKR) on 17 October 2008. On this occasion, the Radio and Plasma Wave Science (RPWS) experiment detected both local and distant radio sources, while plasma parameters were measured in situ by the magnetometer and the Cassini Plasma Spectrometer. A goniopolarimetric inversion was applied to RPWS three-antenna electric measurements to determine the wave vector k and the complete state of polarization of detected waves. We identify broadband extraordinary (X) mode as well as narrowband ordinary (O) mode SKR at low frequencies. Within the source region, SKR is emitted just above the X mode cutoff frequency in a hot plasma, with a typical electron-to-wave energy conversion efficiency of 1% (2% peak). The knowledge of the k vector is then used to derive the locus of SKR sources in the kronian magnetosphere, which shows X and O components emanating from the same regions. We also compute the associated beaming angle at the source theta' = (k, -B) either from (1) in situ measurements or a model of the magnetic field vector (for local to distant sources) or (2) polarization measurements (for local sources). Obtained results, similar for both modes, suggest quasi-perpendicular emission for local sources, whereas the beaming pattern of distant sources appears as a hollow cone with a frequency-dependent constant aperture angle: theta' = 75° ± 15° below 300 kHz, decreasing at higher frequencies to reach theta' (1000 kHz) = 50° ± 25°. Finally, we investigate quantitatively the SKR polarization state, observed to be strongly elliptical at the source, and quasi-purely circular for sources located beyond approximately two kronian radii. We show that conditions of weak mode coupling are achieved along the raypath, under which the magnetoionic theory satisfactorily describes the evolution of the observed polarization. These results are analyzed comparatively with the auroral kilometric radiation at Earth. (10.1029/2010JA016195)
  DOI : 10.1029/2010JA016195
• Estimation of the Gas Temperature of NO during a DC Plasma Pulse using Quantum Cascade Laser (QCL) Absorption Spectroscopy
  
  • Hübner M.
  • Marinov Daniil
  • Guaitella Olivier
  • Rousseau Antoine
  • Roepcke J.
  , 2011.
• Observation and theoretical modeling of electron scale solar wind turbulence
  
  • Sahraoui Fouad
  • Goldstein M. L.
  • Abdul-Kader K.
  • Belmont Gérard
  • Rezeau Laurence
  • Robert Patrick
  • Canu Patrick
  Comptes Rendus. Physique, Académie des sciences (Paris), 2011, 12 (2), pp.132-140. Turbulence at MagnetoHydroDynamics (MHD) scales in the solar wind has been studied for more than three decades, using data analysis, theoretical and numerical modeling. However, smaller scales have not been explored until very recently. Here, we review recent results on the first observation of cascade and dissipation of the solar wind turbulence at the electron scales. Thanks to the high resolution magnetic and electric field data of the Cluster spacecraft, we computed the spectra of turbulence up to (in the spacecraft reference frame) and found evidence of energy dissipation around the Doppler-shifted electron gyroscale . Before its dissipation, the energy is shown to undergo two cascades: a Kolmogorov-like cascade with a scaling above the proton gyroscale, and a new cascade at the sub-proton and electron gyroscales. Above the spectrum has a steeper power law down to the noise level of the instrument. Solving numerically the linear MaxwellVlasov equations combined with recent theoretical predictions of the Gyro-Kinetic theory, we show that the present results are consistent with a scenario of a quasi-two-dimensional cascade into Kinetic Alfvén modes (KAW). New analyses of other data sets, where the Cluster separation (of about ) allowed us to explore the sub-proton scales using the k-filtering technique, and to confirm the 2D nature of the turbulence at those scales. (10.1016/j.crhy.2010.11.008)
  DOI : 10.1016/j.crhy.2010.11.008