Publications

2011

• Solar Wind turbulence, from MHD to electron scales
  
  • Sahraoui Fouad
  • Belmont Gérard
  • Goldstein M. L.
  • Huang S. Y.
  • Kiyani K. H.
  • Narita Y.
  , 2011.
• On efficient renormalization of the ITG mode
  
  • Gürcan Özgür D.
  , 2011 (Oral). http://perso.ens-lyon.fr/nicolas.plihon/HOUCHES
• RF waveform tailoring to control film morphology during nanocrystalline silicon PECVD
  
  • Booth Jean-Paul
  • Johnson E.V.
  • Delattre Pierre-Alexandre
  • Verbeke T.
  • Vanel J-C
  , 2011.
• Simulation numérique de la reconnexion magnétique : mécanismes cinétiques sous-jacents à la description fluide des ions
  
  • Aunai Nicolas
  , 2011. La capacité à libérer l’énergie stockée dans le champ magnétique et à briser le théorème du gel font de la reconnexion magnétique un des phénomènes les plus importants de la physique des plasmas. Lorsqu’elle se produit dans un environnement non-collisionel comme la magnétosphère terrestre, une modélisation cinétique est à priori nécessaire. Cependant la plupart de notre compréhension du phénomène se base sur un interprétation fluide, plus intuitive. Dans quelle mesure ces deux interprétations d’un même phénomène sont-elles reliées ? C’est la problématique à laquelle cette thèse s’intéresse, dans le cas de la reconnexion antiparallèle et pour la population ionique du plasma. La première partie de ce travail s’intéresse à l’accélération fluide et cinétique des protons au sein de la région de reconnexion. Il est montré comment le mouvement individuel des particules joue un rôle du point de vue fluide via la force de pression, jusqu’alors négligée dans les modèles. Ces résultats ont également mené dans une seconde partie à des prédictions et vérifications observationnelles basées sur les données des satellites Cluster. Dans un troisième temps, nous montrons le rôle important joué par le flux d’énergie thermique dans le transfert d’énergie au cours du processus de reconnexion, dans le cas symétrique et asymétrique. Enfin la dernière partie de ce manuscrit propose une solution au problème fondamental consistant décrire une couche de courant tangentielle asymétrique dans un état d’équilibre cinétique
• Seeing Inside Plasma Etch Reactors: from diagnostics to sensors for control
  
  • Booth Jean-Paul
  • Chabert Pascal
  • Sarot Rodolphe
  • Zaka-Ul-Islam Mujahid
  , 2011.
• Space Weather : An introduction
  
  • Amory-Mazaudier Christine
  , 2011.
• Space Weather : An Introduction
  
  • Amory-Mazaudier Christine
  , 2011.
• Time variations of the ionosphere at the northern tropical crest of ionization at Phu Thuy, Vietnam
  
  • Pham Thi Thu Hong
  • Amory-Mazaudier Christine
  • Le Huy M.
  Annales Geophysicae, European Geosciences Union, 2011, pp.197-207. This study is the first which gives the climatology of the ionosphere at the northern tropical crest of ionization in the Asian sector. We use the data from Phu Thuy station, in Vietnam, through three solar cycles (20, 21 and 22), showing the complete morphology of ionosphere parameters by analyzing long term variation, solar cycle variation and geomagnetic activity effects, seasonal evolution and diurnal development. Ionospheric critical frequencies, foF2, foF1 and foE, evolve according to the 11-year sunspot cycle. Seasonal variations show that foF2 exhibits a semiannual pattern with maxima at equinox, and winter and equinoctial anomalies depending on the phases of the sunspot solar cycle. 1foF2 exhibits a semiannual variation during the minimum phase of the sunspot solar cycle 20 and the increasing and decreasing phases of solar cycle 20, 21 and 22. 1foF1 exhibits an annual variation during the maximum phase of solar cycles 20, 21 and 22. 1h0F2 shows a regular seasonal variation for the different solar cycles while 1h0F1 exhibits a large magnitude dispersion from one sunspot cycle to another. The long term variations consist in an increase of 1.0MHz for foF2 and of 0.36MHz for foF1. foE increases 0.53MHz from solar cycle 20 to solar cycle 21 and then decreases −0.23MHz during the decreasing phase of cycle 21. The diurnal variation of the critical frequency foF2 shows minima at 05:00 LT and maxima around 14:00 LT. foF1 and foE have a maximum around noon. The diurnal variation of h0F2 exhibits a maximum around noon. The main features of h0F1 are a minimum near noon and the maximum near midnight. Other minima and maxima occur in the morning, at about 04:00 or 05:00 LT and in the afternoon, at about 18:00 or 19:00 LT but they are markedly smaller. Only during the maximum phase of all sunspot solar cycles the maximum near 19:00 LT is more pronounced. (10.5194/angeo-29-197-2011)
  DOI : 10.5194/angeo-29-197-2011
• Modeling Some Calibrated Cracks for E-NDE by a Difference Method
  
  • Bettaieb Laroussi
  • Kokabi Hamid
  • Poloujadoff Michel
  • Coillot Christophe
  Journal of Nondestructive Evaluation, Springer Verlag, 2011, 30 (3), pp.117 - 121. Electromagnetic Non Destructive Evaluation (E-NDE) is often conducted by inducing eddy currents in the structure to be examined, if this is conducting. Existence of flaws is detected by difference between the response of defect-free structures and damaged ones. In the present paper, we model such processes in order to predict the feasibility of this evaluation and to facilitate the interpretation of the observation. An original method is to represent a crack by a current source producing a magnetic signal. We have applied it to the case of a defect with a standard shape. The experimental evidences for the validity of this method are given. (10.1007/s10921-011-0097-5)
  DOI : 10.1007/s10921-011-0097-5
• 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.
  , 2011. 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 θ‧ = (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: θ‧ = 75° ± 15° below 300 kHz, decreasing at higher frequencies to reach θ‧ (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.
• Sq field characteristics at Phu Thuy, Vietnam, during solar cycle 23: comparisons with Sq field in other longitude sectors
  
  • Pham Thi Thu Hong
  • Amory-Mazaudier Christine
  • Le Huy M.
  Annales Geophysicae, European Geosciences Union, 2011, pp.1-17. Quiet days variations in the Earth's magnetic field (the Sq current system) are compared and contrasted for the Asian, African and American sectors using a new dataset from Vietnam. This is the first presentation of the variation of the Earth's magnetic field (Sq), during the solar cycle 23, at Phu Thuy, Vietnam (geographic latitudes 21.03 N and longitude: 105.95 E). Phu Thuy observatory is located below the crest of the equatorial fountain in the Asian longitude sector of the Northern Hemisphere. The morphology of the Sq daily variation is presented as a function of solar cycle and seasons. The diurnal variation of Phu Thuy is compared to those obtained in different magnetic observatories over the world to highlight the characteristics of the Phu Thuy observations. In other longitude sectors we find different patterns. At Phu Thuy the solar cycle variation of the amplitude of the daily variation of the X component is correlated to the F.10.7 cm solar radiation ( 0.74). This correlation factor is greater than the correlation factor obtained in two observatories located at the same magnetic latitudes in other longitude sectors: at Tamanrasset in the African sector ( 0.42, geographic latitude 22.79) and San Juan in the American sector ( 0.03, geographic latitude 18.38). At Phu Thuy, the Sq field exhibits an equinoctial and a diurnal asymmetry: - The seasonal variation of the monthly mean of X component exhibits the well known semiannual pattern with 2 equinox maxima, but the X component is larger in spring than in autumn. Depending of the phase of the sunspot cycle, the maximum amplitude of the X component varies in spring from 30 nT to 75 nT and in autumn from 20 nT to 60 nT. The maximum amplitude of the X component exhibits roughly the same variation in both solstices, varying from about 20 nT to 50 nT, depending on the position into the solar cycle. - In all seasons, the mean equinoctial diurnal Y component has a morning maximum Larger than the afternoon minimum i.e. the equivalent current flow over a day is more southward than northward. During winter, the asymmetry is maximum, it erases the afternoon minimum. At the Gnangara observatory, in Asian Southern Hemisphere, the diurnal Y pattern is opposite and the current flow is more northward. It seems that in the Asian sector, the northern and southern Sq current cells both contribute strongly to the equatorial electrojet. The pattern is different in the African and American sectors where the northern Sq current cell contribution to the equatorial electrojet is smaller than the southern one. These observations can explain the unexpected maximum of amplitude of the equatorial electrojet observed in the Asian sector where the internal field is very large. During winter the Y component flow presents an anomaly, it is always southward during the whole day and there is no afternoon northward circulation. (10.5194/angeo-29-1-2011)
  DOI : 10.5194/angeo-29-1-2011
• 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
• 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.
• 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
• 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
• 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
• 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
• 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
• 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
• Collective Light Scattering for the Study of Fluctuations in Magnetized Plasmas: The Hall Thruster Case Study
  
  • Tsikata Sedina
  • Honoré Cyrille
  • Grésillon D.
  • Lemoine N.
  Contributions to Plasma Physics, Wiley-VCH Verlag, 2011, 51 (2-3), pp.119-125. Collective light scattering (CLS) has been recently extended to the observation of Hall effect thruster plasmas. A better understanding of the physics of Hall thrusters is key to improving thruster operation and lifetimes. In particular, the origins of thruster phenomena such as anomalous electron transport need to be determined. A high-performance CLS diagnostic has therefore been developed for identifying and measuring electron density fluctuations in the thruster, at millimetric length scales and MHz frequencies. Such modes are believed to play a role in anomalous transport, and experiments so far performed have provided information on their dispersion relations, amplitude and directivity. This work describes the technical aspects of the optical bench and the range of accessible experiments (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) (10.1002/ctpp.201000057)
  DOI : 10.1002/ctpp.201000057
• 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&#8722; 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&#8722; 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&#8722; ion extraction, while it drastically decreases the extracted electron current. Secondly, the extracted H&#8722; 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
• Electron-cylotron maser radiation from electron holes: upward current region
  
  • Treumann R. A.
  • Baumjohann W.
  • Pottelette R.
  Annales Geophysicae, European Geosciences Union, 2011, 29, pp.1885-1904. Electron holes are suggested to be an important source for generation of electron-cyclotron maser radiation. We demonstrate that electron holes generated in a ring-horseshoe distribution in the auroral-kilometric radiation source region have the capacity to emit band-limited radiation. The radiation is calculated in the proper frame of a circular model hole and shown to be strictly perpendicular in this frame. Its bandwidth under auroral conditions is of the order of ~1 kHz, which is a reasonable value. It is also shown that much of the drift of fine structure in the radiation can be interpreted as Doppler shift. Estimates based on data are in good agreement with theory. Growth and absorption rates have been obtained for the emitted radiation. However, the growth rate of a single hole obtained under conservative conditions is small, too small for reproducing the observed fine structure flux. Trapping of radiation inside the hole for the hole's lifetime helps amplifying the radiation additionally but introduces other problems. This entire set of questions is discussed at length and compared to radiation from the global horseshoe distribution. The interior of the hole produces a weak absorption at slightly higher frequency than emission. The absorptivity is roughly two orders of magnitude below the growth rate of the radiation thus being weak even when the emission and absorption bands overlap. Transforming to the stationary observer's frame it is found that the radiation becomes oblique against the magnetic field. For approaching holes the radiated frequencies may even exceed the local electron cyclotron frequency. (10.5194/angeo-29-1885-2011)
  DOI : 10.5194/angeo-29-1885-2011
• 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
• 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
• 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