Publications

2014

• Adsorption and reactivity of nitrogen atoms on silica surface under plasma exposure
  
  • Marinov Daniil
  • Guaitella Olivier
  • Arcos T. de Los
  • von Keudell A.
  • Rousseau Antoine
  Journal of Physics D: Applied Physics, IOP Publishing, 2014, 47 (47), pp.475204. The kinetics of adsorption, desorption and recombination of nitrogen atoms on a silica surface is investigated. Stable nitrogen atoms are grafted to the inner surface of a fused silica discharge tube by a discharge in N 2 at 0.53?mbar. After the pre-treatment, the surface is analysed using x-ray photoelectron spectroscopy and an isotopic exchange technique. The latter consists of the exposure of the pre-treated surface with a discharge in the heavy nitrogen isotope 30 N 2 . Nitrogen isotopologues 29 N 2 and 28 N 2 produced on the surface are detected using a mass spectrometer and provide information about the coverage and reactivity of adsorbed 14 N atoms. It is found that during the pre-treatment, a silicon oxynitride (SiO x N y ) layer is formed on the initially clean SiO 2 surface. The coverage of N on the surface increases from 5? × ?10 13 to 5? × ?10 15? cm ?2 for a pre-treatment duration in the range of 10 ?2 ? 10 4 ?s. Atoms on the surface demonstrate a distribution of reactivity, which is attributed to a distribution of their binding energies and configurations on the surface. We demonstrate that stable chemisorbed N ads are not the main recombination sites for N atoms on the surface contrary to previous studies. We conclude that recombination takes place mainly on weakly bonding active sites with the binding energy smaller than 1?eV. (10.1088/0022-3727/47/47/475204)
  DOI : 10.1088/0022-3727/47/47/475204
• Kinetic Turbulence in the Terrestrial Magnetosheath: Cluster Observations
  
  • Huang S. Y.
  • Sahraoui Fouad
  • Deng X. H.
  • He J. S.
  • Yuan Z. G.
  • Zhou M.
  • Pang Y.
  • Fu H.S.
  The Astrophysical Journal Letters, Bristol : IOP Publishing, 2014, 789, pp.L28. We present a first statistical study of subproton- and electron-scale turbulence in the terrestrial magnetosheath using waveform data measured by the Cluster/STAFF search coil magnetometer in the frequency range [1, 180] Hz. It is found that clear spectral breaks exist near the electron scale, which separate two power-law-like frequency bands referred to as the dispersive and the electron dissipation ranges. The frequencies of the breaks f<SUB>b</SUB> are shown to be well correlated with the electron gyroscale rho <SUB>e</SUB> rather than with the electron inertial length d<SUB>e</SUB> . The distribution of the slopes below f<SUB>b</SUB> is found to be narrow and peaks near -2.9, while that of the slopes above f<SUB>b</SUB> is found to be broader, peaking near -5.2, with values as low as -7.5. This is the first time that such steep power-law spectra are reported in space plasma turbulence. These observations provide new constraints on theoretical modeling of kinetic turbulence and dissipation in collisionless magnetized plasmas. (10.1088/2041-8205/789/2/L28)
  DOI : 10.1088/2041-8205/789/2/L28
• Characteristics of the flank magnetopause: Cluster observations
  
  • Haaland S.
  • Reistad J.
  • Tenfjord P.
  • Gjerloev J.
  • Maes Lukas
  • de Keyser J.
  • Maggiolo R.
  • Anekallu C.
  • Dorville Nicolas
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2014, 119, pp.9019-9037. The magnetopause is a current sheet forming the boundary between the geomagnetic field on one side and the shocked solar wind on the other side. This paper discusses properties of the low-latitude dawn and dusk flanks of the magnetopause. The reported results are based on a large number of measurements obtained by the Cluster satellites during magnetopause traversals. Using a combination of single-spacecraft and multispacecraft techniques, we calculated macroscopic features such as thickness, location, and motion of the magnetopause. The results show that the typical flank magnetopause is significantly thicker than the dayside magnetopause and also possesses a pronounced and persistent dawn-dusk asymmetry. Thicknesses vary from 150 to 5000&#8201;km, with an median thickness of around 1400&#8201;km at dawn and around 1150&#8201;km at dusk. Current densities are on average higher on dusk, suggesting that the total current at dawn and dusk are similar. Solar wind conditions and the interplanetary magnetic field cannot fully explain the observed dawn-dusk asymmetry. For a number of crossings we were also able to derive detailed current density profiles. The profiles show that the magnetopause often consists of two or more adjacent current sheets, each current sheet typically several ion gyroradii thick and often with different current direction. This demonstrates that the flank magnetopause has a structure that is more complex than the thin, one-dimensional current sheet described by a Chapman-Ferraro layer. (10.1002/2014JA020539)
  DOI : 10.1002/2014JA020539
• A review on ion-ion plasmas created in weakly magnetized electronegative plasmas
  
  • Aanesland Ane
  • Bredin Jérôme
  • Chabert Pascal
  Plasma Sources Science and Technology, IOP Publishing, 2014, 23 (4), pp.044003. IonIon plasmas are electronegative plasmas where the electron density is several orders of magnitude lower than the negative ion density. These plasmas have been scarcely observed and investigated since the 1960s and are formed as a transient state of pulsed plasmas or in separate regions in magnetized plasmas. In this review we focus on the latter case of continuous formation of ionion plasmas created at the periphery of magnetized plasma columns or downstream localized magnetic barriers. We bring together and review experimental results already published elsewhere and complement them with new results to illustrate the physics important in ionion plasma formation and highlight in particular unanswered questions. We show that with a good design the density in the ionion region is dropping only by a factor of 23 from the initial plasma density. These plasmas can therefore be well suited for various ion source applications when both fluxes or beams of positive and negative ions are desired, and when electrons can cause harmful effects. (10.1088/0963-0252/23/4/044003)
  DOI : 10.1088/0963-0252/23/4/044003
• Modelling Ganymede's neutral environment: A 3D test-particle simulation
  
  • Turc Lucile
  • Leclercq Ludivine
  • Leblanc François
  • Modolo Ronan
  • Chaufray Jean-Yves
  Icarus, Elsevier, 2014, 229, pp.157-169. In this paper, we present a 3D parallelized test-particle model of Ganymede's neutral environment. The atmosphere sources are assumed to be the sputtering and the sublimation of water-ice, the former taking place in the polar regions and the latter near the subsolar point. It appears that Ganymede's atmosphere is deeply structured by these two processes, leading to a strong dichotomy between polar and subsolar regions. The densest part of the atmosphere is found in the vicinity of the subsolar point, where sublimated H2O is the predominant species near the surface. At higher latitudes and on the nightside, O2 prevails at low altitude, whereas the high altitudes are primarily populated by H2 everywhere in the atmosphere. An estimation of the number of collisions shows that the atmosphere is mostly collisionless, except a small region near the subsolar point. The O2 column density in our model is in good agreement with the observations. However, it appears that we underestimate the H density. This could suggest that the sublimation rates are significantly underestimated but not the sputtering. The escape rates of the different species are essentially lower than those previously obtained by Marconi (2007). The effects of varying surface emission fluxes are investigated in order to simulate Ganymede's passing into the shadow of Jupiter or in the plasma sheet. We estimate that the sublimated H2O peak in the subsolar region would disappear within one hour in the shadow of Jupiter. Likewise, the variation of the sputtering fluxes alters the atmospheric structure in a similar time scale. (10.1016/j.icarus.2013.11.005)
  DOI : 10.1016/j.icarus.2013.11.005
• Wave number determination of Pc 1-2 mantle waves considering He++ ions: A Cluster study
  
  • Grison B.
  • Escoubet C. Philippe
  • Santolík O.
  • Cornilleau-Wehrlin Nicole
  • Khotyaintsev Y. V.
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2014, 119 (9), pp.7601-7614. The present case study concerns narrowband electromagnetic emission detected in the distant cusp region simultaneously with upgoing plasma flows. The wave properties match the usual properties of the Pc 12 mantle waves: small angle between the wave vector and the magnetic field line, left-hand polarization, and propagation toward the ionosphere. We report here the first direct wave vector measurement of these waves (about 1.2&#8201;×&#8201;10&#8722;&#8201;2&#8201;rad/km) through multi spacecraft analysis using the three magnetic components and, at the same time, through single spacecraft analysis based on the refractive index analysis using the three magnetic components and two electric components. The refractive index analysis offers a simple way to estimate wave numbers in this frequency range. Numerical calculations are performed under the observed plasma conditions. The obtained results show that the ion distribution functions are unstable to ion cyclotron instability at the observed wave vector value, due to the large ion temperature anisotropy. We thus show that these electromagnetic ion cyclotron (EMIC) waves are amplified in the distant cusp region. The Poynting flux of the waves is counterstreaming with respect to the plasma flow. This sense of propagation is consistent with the time necessary to amplify the emissions to the observed level. We point out the role of the wave damping at the He gyrofrequency to explain that such waves cannot be observed from the ground at the cusp foot print location. (10.1002/2013JA019719)
  DOI : 10.1002/2013JA019719
• A Kolmogorov-like exact relation for compressible polytropic turbulence
  
  • Banerjee Supratik
  • Galtier Sébastien
  Journal of Fluid Mechanics, Cambridge University Press (CUP), 2014, 742, pp.230-242. Compressible hydrodynamic turbulence is studied under the assumption of a polytropic closure. Following Kolmogorov, we derive an exact relation for some two-point correlation functions in the asymptotic limit of a high Reynolds number. (10.1017/jfm.2013.657)
  DOI : 10.1017/jfm.2013.657
• Modelling of JET hybrid scenarios with GLF23 transport model: E x B shear stabilization of anomalous transport
  
  • Voitsekhovitch I.
  • Belo P.
  • Citrin Jonathan
  • Fable E.
  • Ferreira Jorge
  • Garcia J.
  • Garzotti L.
  • Hobirk J.
  • Hogeweij G.M.D.
  • Joffrin E.
  • Koechl F.
  • Litaudon X.
  • Moradi S.
  • Nabais F.
  • Jet-Efda Contributors
  • Eu-Itm Iter Scenario Modelling Grp
  Nuclear Fusion, IOP Publishing, 2014, 54 (9). The E x B shear stabilization of anomalous transport in JET hybrid discharges is studied via self-consistent predictive modelling of electron and ion temperature, ion density and toroidal rotation velocity performed with the GLF23 model. The E x B shear stabilization factor (parameter alpha E in the GLF23 model) is adjusted to predict accurately the four simulated quantities under different experimental conditions, and the uncertainty in aE determined by 15% deviation between simulated and measured quantities is estimated. A correlation of aE with toroidal rotation velocity and E x B shearing rate is found in the low density plasmas, suggesting that the turbulence quench rule may be more complicated than assumed in the GLF23 model with constant alpha(E). For the selected discharges the best predictive accuracy is obtained by using weak/no E x B shear stabilization (i.e. alpha(E) approximate to 0) at low toroidal angular frequency (Omega < 60 krad s(-1)), even in the scenarios with the current overshoot, and alpha(E) = 0.9 at high frequency (Omega > 100 krad s(-1)). Interestingly, a weak E x B shear stabilization of anomalous transport is found in the medium density strongly rotating discharge. An importance of linear beta(e) stabilization in this discharge is estimated and compared to the low density discharge with equally high beta(e). The toroidal rotation velocity is well predicted here by assuming that the momentum diffusion coefficient is a fraction of thermal ion diffusivity. Taking into account the alpha(E) and Prandtl number with their uncertainties determined in the modelling of JET hybrid discharges, the performance of ITER hybrid scenario with optimized heat mix (33 MW of NBI and 20 MW of ECCD) is estimated showing the importance of toroidal rotation for achieving Q > 5. (10.1088/0029-5515/54/9/093006)
  DOI : 10.1088/0029-5515/54/9/093006
• On the electron diffusion region in planar, asymmetric, systems
  
  • Hesse Michael
  • Aunai Nicolas
  • Sibeck David G.
  • Birn Joachim
  Geophysical Research Letters, American Geophysical Union, 2014, 41, pp.8673-8680. Particle-in-cell simulations and analytical theory are employed to study the electron diffusion region in asymmetric reconnection, which is taking place in planar configurations without a guide field. The analysis presented here focuses on the nature of the local reconnection electric field and on differences from symmetric configurations. Further emphasis is on the complex structure of the electron distribution in the diffusion region, which is generated by the mixing of particles from different sources. We find that the electric field component that is directly responsible for flux transport is provided not by electron pressure-based, "quasi-viscous," terms but by inertial terms. The quasi-viscous component is shown to be critical in that it is necessary to sustain the required overall electric field pattern in the immediate neighborhood of the reconnection X line. (10.1002/2014GL061586)
  DOI : 10.1002/2014GL061586
• Coherent structures in ion temperature gradient turbulence-zonal flow
  
  • Singh Rameswar
  • Singh R.
  • Kaw P.
  • Gürcan Özgür D.
  • Diamond P.H.
  Physics of Plasmas, American Institute of Physics, 2014, 21 (10), pp.102306. Nonlinear stationary structure formation in the coupled ion temperature gradient (ITG)-zonal flow system is investigated. The ITG turbulence is described by a wave-kinetic equation for the action density of the ITG mode, and the longer scale zonal mode is described by a dynamic equation for the m&#8201;=&#8201;n&#8201;=&#8201;0 component of the potential. Two populations of trapped and untrapped drift wave trajectories are shown to exist in a moving frame of reference. This novel effect leads to the formation of nonlinear stationary structures. It is shown that the ITG turbulence can self-consistently sustain coherent, radially propagating modulation envelope structures such as solitons, shocks, and nonlinear wave trains. (10.1063/1.4898207)
  DOI : 10.1063/1.4898207
• Global (volume-averaged) model of inductively coupled chlorine plasma: Influence of Cl wall recombination and external heating on continuous and pulse-modulated plasmas
  
  • Kemaneci Efe
  • Carbone Emile
  • Booth Jean-Paul
  • Graef Wouter
  • van Dijk Jan
  • Kroesen G.
  Plasma Sources Science and Technology, IOP Publishing, 2014, 23 (4), pp.045002. An inductively coupled radio-frequency plasma in chlorine is investigated via a global (volume-averaged) model, both in continuous and square wave modulated power input modes. After the power is switched off (in a pulsed mode) an ion?ion plasma appears. In order to model this phenomenon, a novel quasi-neutrality implementation is proposed. Several distinct Cl wall recombination probability measurements exist in the literature, and their effect on the simulation data is compared. We also investigated the effect of the gas temperature that was imposed over the range 300?1500 K, not calculated self-consistently. Comparison with published experimental data from several sources for both continuous and pulsed modes shows good agreement with the simulation results. (10.1088/0963-0252/23/4/045002)
  DOI : 10.1088/0963-0252/23/4/045002
• Plasma-catalyst coupling for volatile organic compound removal and indoor air treatment: a review
  
  • Thévenet Frédéric
  • Sivachandiran Loganathan
  • Guaitella Olivier
  • Barakat Christelle
  • Rousseau Antoine
  Journal of Physics D: Applied Physics, IOP Publishing, 2014, 47 (22), pp.224011. The first part of the review summarizes the problem of air pollution and related air-cleaning technologies. Volatile organic compounds in particular have various effects on health and their abatement is a key issue. Different ways to couple non-thermal plasmas with catalytic or adsorbing materials are listed. In particular, a comparison between in-plasma and post-plasma coupling is made. Studies dealing with plasma-induced heterogeneous reactivity are analysed, as well as the possible modifications of the catalyst surface under plasma exposure. As an alternative to the conventional and widely studied plasmacatalyst coupling, a sequential approach has been recently proposed whereby pollutants are first adsorbed onto the material, then oxidized by switching on the plasma. Such a sequential approach is reviewed in detail. (10.1088/0022-3727/47/22/224011)
  DOI : 10.1088/0022-3727/47/22/224011
• The quasi-electrostatic mode of chorus waves and electron nonlinear acceleration
  
  • Agapitov O. V.
  • Artemyev A.V.
  • Mourenas D
  • Krasnoselskikh V
  • Bonnell J
  • Le Contel Olivier
  • Cully C. M.
  • Angelopoulos V
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2014, 119, pp.1606-1626. Selected Time History of Events and Macroscale Interactions During Substorms observations at medium latitudes of highly oblique and high-amplitude chorus waves are presented and analyzed. The presence of such very intense waves is expected to have important consequences on electron energization in the magnetosphere. An analytical model is therefore developed to evaluate the efficiency of the trapping and acceleration of energetic electrons via Landau resonance with such nearly electrostatic chorus waves. Test-particle simulations are then performed to illustrate the conclusions derived from the analytical model, using parameter values consistent with observations. It is shown that the energy gain can be much larger than the initial particle energy for 10 keV electrons, and it is further demonstrated that this energy gain is weakly dependent on the density variation along field lines. (10.1002/2013JA019223)
  DOI : 10.1002/2013JA019223
• Evolution of Turbulence in the Expanding Solar Wind, a Numerical Study
  
  • Dong Yue
  • Verdini Andrea
  • Grappin Roland
  The Astrophysical Journal, American Astronomical Society, 2014, 793, pp.118. We study the evolution of turbulence in the solar wind by solving numerically the full three-dimensional (3D) magnetohydrodynamic (MHD) equations embedded in a radial mean wind. The corresponding equations (expanding box model or EBM) have been considered earlier but never integrated in 3D simulations. Here, we follow the development of turbulence from 0.2 AU up to about 1.5 AU. Starting with isotropic spectra scaling as k <SUP>-1</SUP>, we observe a steepening toward a k <SUP>-5/3</SUP> scaling in the middle of the wave number range and formation of spectral anisotropies. The advection of a plasma volume by the expanding solar wind causes a non-trivial stretching of the volume in directions transverse to radial and the selective decay of the components of velocity and magnetic fluctuations. These two effects combine to yield the following results. (1) Spectral anisotropy: gyrotropy is broken, and the radial wave vectors have most of the power. (2) Coherent structures: radial streams emerge that resemble the observed microjets. (3) Energy spectra per component: they show an ordering in good agreement with the one observed in the solar wind at 1 AU. The latter point includes a global dominance of the magnetic energy over kinetic energy in the inertial and f <SUP>-1</SUP> range and a dominance of the perpendicular-to-the-radial components over the radial components in the inertial range. We conclude that many of the above properties are the result of evolution during transport in the heliosphere, and not just the remnant of the initial turbulence close to the Sun. (10.1088/0004-637X/793/2/118)
  DOI : 10.1088/0004-637X/793/2/118
• Ion flux asymmetry in radiofrequency capacitively-coupled plasmas excited by sawtooth-like waveforms
  
  • Bruneau Bastien
  • Novikova T.
  • Lafleur Trevor
  • Booth Jean-Paul
  • Johnson E.V.
  Plasma Sources Science and Technology, IOP Publishing, 2014, 23 (6), pp.065010. Using particle-in-cell simulations, we predict that it is possible to obtain a significant difference between the ion flux to the powered electrode and that to the grounded electrode?with about 50% higher ion flux on one electrode?in a geometrically symmetric, radiofrequency capacitively-coupled plasma reactor by applying a non-sinusoidal, ?Tailored? voltage waveform. This sawtooth-like waveform presents different rising and falling slopes over one cycle. We show that this effect is due to differing plasma sheath motion in front of each electrode, which induces a higher ionization rate in front of the electrode which has the fastest positive rising voltage. Together with the higher ion flux comes a lower voltage drop across the sheath, and therefore a reduced maximum ion bombardment energy; a result in contrast to typical process control mechanisms. (10.1088/0963-0252/23/6/065010)
  DOI : 10.1088/0963-0252/23/6/065010
• Plasma-assisted ignition and combustion: nanosecond discharges and development of kinetic mechanisms
  
  • Starikovskaia Svetlana
  Journal of Physics D: Applied Physics, IOP Publishing, 2014, 47 (35), pp.353001 (34pp). This review covers the results obtained in the period 20062014 in the field of plasma-assisted combustion, and in particular the results on ignition and combustion triggered or sustained by pulsed nanosecond discharges in different geometries. Some benefits of pulsed high voltage discharges for kinetic study and for applications are demonstrated. The necessity of and the possibility of building a particular kinetic mechanism of plasma-assisted ignition and combustion are discussed. The most sensitive regions of parameters for plasmacombustion kinetic mechanisms are selected. A map of the pressure and temperature parameters (PT diagram) is suggested, to unify the available data on ignition delay times, ignition lengths and densities of intermediate species reported by different authors. (10.1088/0022-3727/47/35/353001)
  DOI : 10.1088/0022-3727/47/35/353001
• The influence of the geometry and electrical characteristics on the formation of the atmospheric pressure plasma jet
  
  • Sobota Ana
  • Guaitella Olivier
  • Rousseau Antoine
  Plasma Sources Science and Technology, IOP Publishing, 2014, 23, pp.025016. An extensive electrical study was performed on a coaxial geometry atmospheric pressure plasma jet source in helium, driven by 30 kHz sine voltage. Two modes of operation were observed, a highly reproducible low-power mode that features the emission of one plasma bullet per voltage period and an erratic high-power mode in which micro-discharges appear around the grounded electrode. The minimum of power transfer efficiency corresponds to the transition between the two modes. Effective capacitance was identified as a varying property influenced by the discharge and the dissipated power. The charge carried by plasma bullets was found to be a small fraction of charge produced in the source irrespective of input power and configuration of the grounded electrode. The biggest part of the produced charge stays localized in the plasma source and below the grounded electrode, in the range 1.23.3 nC for ground length of 38 mm. (10.1088/0963-0252/23/2/025016)
  DOI : 10.1088/0963-0252/23/2/025016
• What is the size of a floating sheath?
  
  • Chabert Pascal
  Plasma Sources Science and Technology, IOP Publishing, 2014, 23 (6), pp.065042. The size of the positive space charge sheath that forms in front of an object immersed in a plasma and not dc-connected to ground with an external circuit (a floating sheath) is calculated numerically. If the sheath edge is defined as the position at which the ion fluid speed equals the Bohm speed, it is shown that the sheath size varies significantly with the discharge parameters, typically from s float &#8776; 7 &#955; Des to s float &#8776; 14 &#955; Des , where s float is the floating sheath size and &#955; Des is the Debye length at the sheath edge. However, if the sheath edge is defined as a significant departure from quasi-neutrality, then the floating sheath size is almost independent of the discharge parameters and may be approximated by s float &#8776; 5 &#955; Des . (10.1088/0963-0252/23/6/065042)
  DOI : 10.1088/0963-0252/23/6/065042
• Complete multi-field characterization of the geodesic acoustic mode in the TCV tokamak
  
  • de Meijere C. A.
  • Coda S.
  • Huang Z.
  • Vermare Laure
  • Vernay T.
  • Vuille V.
  • Brunner Stephan
  • Dominski J.
  • Hennequin Pascale
  • Kraemer-Flecken A.
  • Merlo G.
  • Porte L.
  • Villard Laurent
  Plasma Physics and Controlled Fusion, IOP Publishing, 2014, 56 (7), pp.072001. The geodesic acoustic mode (GAM) is a coherently oscillating zonal flow that may regulate turbulence in toroidal plasmas. Uniquely, the complete poloidal and toroidal structure of the magnetic component of the turbulence-driven GAM has been mapped in the TCV tokamak. Radially localized measurements of the fluctuating density, ECE radiative temperature and poloidal flow show that the GAM is a fully coherent, radially propagating wave. These observations are consistent with electrostatic, gyrokinetic simulations. (10.1088/0741-3335/56/7/072001)
  DOI : 10.1088/0741-3335/56/7/072001
• Turbulence elasticity-A new mechanism for transport barrier dynamics
  
  • Guo Z. B.
  • Diamond P.H.
  • Kosuga Y.
  • Gürcan Özgür D.
  Physics of Plasmas, American Institute of Physics, 2014, 21 (9). We present a new, unified model of transport barrier formation in ``elastic'' drift wave-zonal flow (DW-ZF) turbulence. A new physical quantity-the delay time (i.e., the mixing time for the DW turbulence)-is demonstrated to parameterize each stage of the transport barrier formation. Quantitative predictions for the onset of limit-cycle-oscillation (LCO) among DW and ZF intensities (also denoted as I-mode) and I-mode to high-confinement mode (H-mode) transition are also given. The LCO occurs when the ZF shearing rate (vertical bar < u >(ZF)'vertical bar) enters the regime Delta omega(k) < vertical bar < V >(ZF)'vertical bar < tau(-1)(cr), where Delta omega(k) is the local turbulence decorrelation rate and tau(cr) is the threshold delay time. In the basic predator-prey feedback system, tau(cr) is also derived. The I-H transition occurs when vertical bar < V >(ExB)'vertical bar > tau(-1)(cr), where the mean E x B shear flow driven by ion pressure ``locks'' the DW-ZF system to the H-mode by reducing the delay time below the threshold value. (C) 2014 AIP Publishing LLC. (10.1063/1.4894695)
  DOI : 10.1063/1.4894695
• Circulation of Heavy Ions and Their Dynamical Effects in the Magnetosphere: Recent Observations and Models
  
  • Kronberg E. A.
  • Ashour-Abdalla M.
  • Dandouras I.
  • Delcourt Dominique C.
  • Grigorenko E. E.
  • Kistler L. M.
  • Kuzichev I. V.
  • Liao J.
  • Maggiolo R.
  • Malova H. V.
  • Orlova K. G.
  • Peroomian V.
  • Shklyar D. R.
  • Shprits Y. Y.
  • Welling D. T.
  • Zelenyi L. M.
  Space Science Reviews, Springer Verlag, 2014, 184 (1-4), pp.173-235. Knowledge of the ion composition in the near-Earths magnetosphere and plasma sheet is essential for the understanding of magnetospheric processes and instabilities. The presence of heavy ions of ionospheric origin in the magnetosphere, in particular oxygen (O ), influences the plasma sheet bulk properties, current sheet (CS) thickness and its structure. It affects reconnection rates and the formation of Kelvin-Helmholtz instabilities. This has profound consequences for the global magnetospheric dynamics, including geomagnetic storms and substorm-like events. The formation and demise of the ring current and the radiation belts are also dependent on the presence of heavy ions. In this review we cover recent advances in observations and models of the circulation of heavy ions in the magnetosphere, considering sources, transport, acceleration, bulk properties, and the influence on the magnetospheric dynamics. We identify important open questions and promising avenues for future research. (10.1007/s11214-014-0104-0)
  DOI : 10.1007/s11214-014-0104-0
• On the origin of falling-tone chorus elements in Earth's inner magnetosphere
  
  • Breuillard H
  • Agapitov O
  • Artemyev A
  • Krasnoselskikh V
  • Le Contel Olivier
  • Cully C. M.
  • Angelopoulos V
  • Zaliznyak Y
  • Rolland G
  Annales Geophysicae, European Geosciences Union, 2014, 32, pp.1477-1485. Generation of extremely/very low frequency (ELF/VLF) chorus waves in Earth's inner magnetosphere has received increased attention recently because of their significance for radiation belt dynamics. Though past theoretical and numerical models have demonstrated how rising-tone chorus elements are produced, falling-tone chorus element generation has yet to be explained. Our new model proposes that weak-amplitude falling-tone chorus elements can be generated by magnetospheric reflection of rising-tone elements. Using ray tracing in a realistic plasma model of the inner magnetosphere, we demonstrate that rising-tone elements originating at the magnetic equator propagate to higher latitudes. Upon reflection there, they propagate to lower L-shells and turn into oblique falling tones of reduced power, frequency, and bandwidth relative to their progenitor rising tones. Our results are in good agreement with comprehensive statistical studies of such waves, notably using magnetic field measurements from THEMIS (Time History of Events and Macroscale Interactions during Substorms) spacecraft. Thus, we conclude that the proposed mechanism can be responsible for the generation of weak-amplitude falling-tone chorus emissions. (10.5194/angeo-32-1477-2014)
  DOI : 10.5194/angeo-32-1477-2014
• The FIELDS Instrument Suite on MMS: Scientific Objectives, Measurements, and Data Products
  
  • Torbert R. B.
  • Russell C. T.
  • Magnes W.
  • Ergun R. E.
  • Lindqvist P.-A.
  • Le Contel Olivier
  • Vaith H.
  • Macri J.
  • Myers S.
  • Rau D.
  • Needell J.
  • King B.
  • Granoff M.
  • Chutter M.
  • Dors I.
  • Olsson G.
  • Khotyaintsev Y. V.
  • Eriksson A.
  • Kletzing C. A.
  • Bounds S.
  • Anderson B.
  • Baumjohann W.
  • Steller M.
  • Bromund K.
  • Le G.
  • Nakamura R.
  • Strangeway R. J.
  • Leinweber H. K.
  • Tucker S.
  • Westfall J.
  • Fischer D.
  • Plaschke F.
  • Porter J.
  • Lappalainen K.
  Space Science Reviews, Springer Verlag, 2014, pp.1-31. Not Available (10.1007/s11214-014-0109-8)
  DOI : 10.1007/s11214-014-0109-8
• Radiation sources with planar wire arrays and planar foils for inertial confinement fusion and high energy density physics research
  
  • Kantsyrev Viktor L.
  • Chuvatin Alexandre S.
  • Safronova Alla S.
  • Rudakov Leonid I.
  • Esaulov A. A.
  • Velikovich A. L.
  • Shrestha Ishor
  • Astanovitsky A.
  • Osborne Glenn C.
  • Shlyaptseva V. V.
  • Weller Michael E.
  • Keim S.
  • Stafford A.
  • Cooper M. C.
  Physics of Plasmas, American Institute of Physics, 2014, 21 (03), pp.031204. This article reports on the joint success of two independent lines of research, each of them being a multi-year international effort. One of these is the development of innovative sources, such as planar wire arrays (PWAs). PWAs turned out to be a prolific radiator, which act mainly as a resistor, even though the physical mechanism of efficient magnetic energy conversion into radiation still remains unclear. We review the results of our extensive studies of PWAs. We also report the new results of the experimental comparison PWAs with planar foil liners (another promising alternative to wire array loads at multi-mega-ampere generators). Pioneered at UNR, the PWA Z-pinch loads have later been tested at the Sandia National Laboratories (SNL) on the Saturn generator, on GIT-12 machine in Russia, and on the QiangGuang-1 generator in China, always successfully. Another of these is the drastic improvement in energy efficiency of pulsed-power systems, which started in early 1980s with Zucker's experiments at Naval Research Laboratory (NRL). Successful continuation of this approach was the Load Current Multiplier (LCM) proposed by Chuvatin in collaboration with Rudakov and Weber from NRL. The 100&#8201;ns LCM was integrated into the Zebra generator, which almost doubled the plasma load current, from 0.9 to 1.7 MA. The two above-mentioned innovative approaches were used in combination to produce a new compact hohlraum radiation source for ICF, as jointly proposed by SNL and UNR [Jones et al., Phys. Rev. Lett. 104, 125001 (2010)]. The first successful proof-of-the-principle experimental implementation of new hohlraum concept at university-scale generator Zebra/LCM is demonstrated. A numerical simulation capability with VisRaD code (from PRISM Co.) established at UNR allowed for the study of hohlraum coupling physics and provides the possibility of optimization of a new hohlraum. Future studies are discussed. (10.1063/1.4865367)
  DOI : 10.1063/1.4865367
• Multi Water Bag modelling of drift kinetic electrons and ions plasmas
  
  • Morel Pierre
  • Dreydemy Ghiro Florent
  • Berionni Vincent
  • Gürcan Özgür D.
  , 2014.