Publications

2016

• New Exact Relations for Helicities in Hall Magnetohydrodynamic Turbulence
  
  • Banerjee Supratik
  • Galtier Sébastien
  , 2016, 18, pp.EPSC2016-7291. Hall magnetohydrodynamics is a mono-fluid plasma model appropriate for probing Finalsome of the physical processes (other than pure kinetic effects) at length scales smaller than the scales of standard MHD. In sub-ionic space plasma turbulence (e.g. the solar wind) this fluid model has been proved to be useful. Three-dimensional incompressible Hall magnetohydrodynamics (MHD) possesses three inviscid invariants which are the total energy, the magnetic helicity and the generalized helicity. In this presentation, we would like to discuss new exact relations for helicities (magnetic helicities and generalized helicities) which are derived for homogeneous stationary (not necessarily isotropic) Hall MHD turbulence (and also for its inertialess electron MHD limit) in the asymptotic limit of large Reynolds numbers. The universal laws are written only in terms of mixed second-order structure functions, i.e. the scalar product of two different increments and are written simply as eta<SUB>M</SUB> = d<SUB>i</SUB> < delta ( b × j) · delta b >, with eta<SUB>M</SUB> the average magnetic helicity flux rate, b the magnetic field, j the current and ± eta<SUB>G</SUB> = < delta ( v × Omega ) · delta Omega > , with eta<SUB>M</SUB> the average generalized helicity flux rate, v the fluid velocity and Omega = b d<SUB>I</SUB> omega being the generalized helicity where omega is simply the fluid vorticity ( = nabla × v). It provides, therefore, a direct measurement of the dissipation rates for the corresponding helicities even in case of an anisotropic plasma turbulence. This study shows that the generalized helicity cascade is strongly linked to the left polarized fluctuations while the magnetic helicity cascade is linked to the right polarized fluctuations. The newly derived relations also show that like energy, a non-zero helicity flux can only be associated to a departure of Beltrami flow state. Reference S. Banerjee & S. Galtier, Chiral Exact Relations for Helicities in Hall Magnetohydrodynamic Turbulence (submitted).
• The role of waves and DC electric fields for electron heating and acceleration in the diffusion region
  
  • Graham Daniel
  • Khotyaintsev Y. V.
  • Vaivads A.
  • Norgren Cecilia
  • Andre M.
  • Lindqvist Per-Arne
  • Le Contel Olivier
  • Ergun Robert
  • Goodrich Katherine
  • Torbert Roy
  • Burch J. L.
  • Russell C. T.
  • Magnes Werner
  • Giles B. L.
  • Pollock Craig
  • Mauk Barry
  • Fuselier Stephen
  , 2016, 18, pp.EPSC2016-10458. Magnetic reconnection is a fundamental process in solar and astrophysical plasmas. The processes operating at electron spatial-scales, which enable magnetic field lines to reconnect, are generally difficult to resolve and identify. However, the recently launched Magnetospheric Multiscale (MMS) mission is specifically designed to resolve electron spatial scales. We use the MMS spacecraft to investigate the process operating within the diffusion region to determine the causes of electron heating and acceleration. In particular, we investigate the type of electrostatic and electromagnetic waves that develop and how they affect the electron distributions. We also compare the roles of wave-particle interactions with DC electric fields to determine which is responsible for the electron heating observed in diffusion regions.
• Multi-Spacecraft Analysis of Plasma Jet Events and Associated Whistler-Wave Emissions using MMS Data
  
  • Breuillard Hugo
  • Le Contel Olivier
  • Retinò Alessandro
  • Chasapis A.
  • Chust Thomas
  • Cohen Ian
  • Wilder Frederick
  • Graham Daniel
  • Khotyaintsev Y. V.
  , 2016, 18, pp.13754. Plasma jets aka bursty bulk flows play a crucial role in Earth's plasmasheet dynamics, in particular during substorms where they can sometimes even penetrate down to the geosynchronous orbit. The energy input from the solar wind is partly dissipated in jet fronts(also called dipolarization fronts) in the form of strong whistler waves that can heat and accelerate energetic electrons. The ratio of the energy transported during jets to the substorm energy consumption is still under debate due to instrumental limitations. In May 2015 the Magnetospheric Multiscale (MMS) mission evolves in a string-of-pearls configuration with an average inter-satellite distance of 300 km which allows us to study in detail the microphysics of these phenomena. Thus in this study we employ MMS data to investigate the properties of jet fronts propagating earthward and their associated whistler-mode wave emissions. We show that the spatial dynamics of jet fronts are of the order of the ion gyroradius and whistler-wave dynamics have a temporal scale of a few seconds. We also investigate the energy dissipation associated with such waves and their interaction with energetic electrons in the vicinity of the flow/jet braking region. In addition, we make use of ray tracing simulations to evaluate their propagation properties, as well as their impact on particles in the off-equatorial magnetosphere.
• The Search-coil Magnetometer for the THOR mission
  
  • Sahraoui Fouad
  • Pinçon Jean-Louis
  • Jannet Guillaume
  • Mansour Malik
  • Henri Pierre
  • Chalumeau Gilles
  • Hachemi Tedjani
  • Jeandet Alexis
  • Briand Nicolas
  • Le Contel Olivier
  • Rezeau Laurence
  , 2016. Turbulence Heating ObserveR (THOR) is the first mission ever flown in space fully dedicated to plasma turbulence. The search-coil magnetometer (SCM) of THOR is a triaxial dual-band antenna dedicated to measuring the magnetic field fluctuations in the frequency range [1Hz,4kHz] and [1,200]kHz. THOR/SCM has a long heritage from earlier space missions such as Cluster, Themis, MMS, BepiColombo, Taranis, Solar orbiter and Solar Probe. In comparison to those missions, the SCM of THOR has a higher sensitivity level, which makes it capable of measuring very low amplitude magnetic fluctuations, in particular in the solar wind. Those measurements are crucial to address the problem of turbulence and energy dissipation at electron scales, a central goal of the THOR mission.
• Testing THEMIS wave measurements against the cold plasma theory
  
  • Taubenschuss U.
  • Santolik O.
  • Le Contel Olivier
  • Bonnell John
  , 2016, 18, pp.7903. The THEMIS (Time History of Events and Macroscale Interactions during Substorms) mission records a multitude of electromagnetic waves inside Earth's magnetosphere and provides data in the form of high-resolution electric and magnetic waveforms. We use multi-component measurements of whistler mode waves and test them against the theory of wave propagation in a cold plasma. The measured ratio cB/E (c is speed of light in vacuum, B is magnetic wave amplitude, E is electric wave amplitude) is compared to the same quantity calculated from cold plasma theory over linearized Faraday's law. The aim of this study is to get estimates for measurement uncertainties, especially with regard to the electric field and the cold plasma density, as well as evaluating the validity of cold plasma theory inside Earth's radiation belts.
• Open questions on particle acceleration in strongly magnetized plasmas and how to answer them
  
  • Berthomier Matthieu
  • Fazakerley A.
  , 2016, 18, pp.EPSC2016-16842. Particle acceleration mechanisms in solar system plasmas usually imply the conversion of electromagnetic energy into particle kinetic energy. These processes may take different forms depending on plasma magnetization but in most cases they involve multi-scale phenomena that cannot be described by ideal MHD. Little evidence has been gathered on how particle acceleration works in strongly magnetized plasmas. We will show how Earth's auroral regions provide the unique opportunity to address the open questions on particle acceleration in low beta plasmas. Single point observations in the auroral regions have suggested that acceleration by Alfvén waves would be responsible for filamentary acceleration along magnetic field lines. In the auroral regions, this mechanism would be associated with the generation of the sub-km scale auroral arcs. However single spacecraft measurements cannot evaluate the energy exchanged over a large volume of space between waves and particles. They cannot assess the efficiency of this mechanism, nor can they tell us where and when it is effective and how it relates to the evolving boundary conditions of the system. Numerical simulations alone cannot fully describe this multi-scale and non-local process in the inhomogeneous auroral plasma. Alternatively, it has been proposed from high-time resolution particle measurements in the auroral regions that localized parallel electric fields would explain the larger scale arcs that can be observed by onboard imagers. Single spacecraft measurements cannot follow the formation and evolution of these transient structures or the complex transport phenomena associated with the strong plasma turbulence that develop along magnetic field lines around these structures. Multi-point CLUSTER observations have shown how these potential acceleration structures were distributed in space and time. However we still miss the dynamic picture of how these structures are created on how they can be maintained in space and time. We will show that the only way to distinguish between these models describing acceleration processes in strongly magnetized plasmas is to combine advanced numerical simulations with high-time resolution in situ measurements, multi-point measurements, and auroral arc imaging. We will describe how the Alfvén mission concept, that will be proposed to the ESA M5 AO, will allow a major breakthrough in our understanding of particle acceleration mechanisms in solar system plasmas.
• Topology of kinetic range turbulence in the solar wind: observations and simulations
  
  • Kiyani K. H.
  • Chapman S. C.
  • Meyrand Romain
  • Sahraoui Fouad
  • Hadid Lina
  • Osman Kareem
  , 2016, 18, pp.EPSC2016-18250. There is now considerable evidence that below ion gyroscales there is a kinetic range of turbulence that shows non-trivial scaling both in the power spectral density and in the higher order moments of fluctuations. We present an investigation of magnetic field fluctuations in sub-ion scale plasma turbulence in the solar wind, using high-cadence measurements from the STAFF search coil instrument on Cluster. We will compare observational results with sub-ion scale fluid model simulations such as Electron MHD and Electron Reduced MHD to shed light on the type of topological coherent structures that we might expect to see on these scales. Our results suggest current sheet domination at the MHD scales transitioning to filament domination at the sub-ion scales, which we attribute to the force-free structures (Beltrami fields) forming from the dominant Hall physics. Comparison of magnetic compressibility ratios (magnetic field component polarization ratios) seen as a function of plasma beta, with those exhibited by the different linear plasma modes from solutions of the linearised compressible Hall-MHD model. These suggest that the fluctuations seen in our observations share polarizations akin to highly oblique (near perpendicular) Alfven and Kinetic Alfven wave modes.
• Turbulence in the solar wind: what controls the slope of the energy spectrum?
  
  • Verdini Andrea
  • Grappin Roland
  , 2016, 18, pp.EPSC2016-8802. The spectrum of solar wind fluctuations is well described by a power law with an average spectral index -5/3 for periods between a few hours and a few minutes. However, the spectral index varies with stream speed and with the correlation of velocity and magnetic field fluctuations (Alfvénicity): the spectrum is softer in fast and Alfvénic streams. Roughly, this variation can be understood in term of the turbulent age of fluctuations at a given scale: the faster is the wind or the stronger is the correlation than the younger is the turbulence. Since the coronal spectrum is supposed to be rather flat (at least in the fast solar wind), smaller spectral indices correspond to less evolved spectra. According to this interpretation, one would expect spectral slope to change with distance as the turbulence ages, while observations report fairly stable spectral slopes. In order to quantify the effect of wind speed and Alfvénicity on the spectral slope, we ran a series of numerical simulations of MHD turbulence in the framework of the Expanding Box Model (EBM). In EBM we can vary the expansion rate and the initial correlation of fluctuations so as to investigate the existence of a threshold value for each parameter or for a combination of the two that could explain the observed variation and stability of the spectral index. We present preliminary results that indicate that the expansion rate does control the spectral index of energy when the Alfvénicity is high.
• Role of the magnetosheath in the interaction of magnetic clouds with the Earth’s magnetosphere
  
  • Fontaine Dominique
  • Turc Lucile
  • Savoini Philippe
  • Modolo Ronan
  , 2016, 18, pp.EGU2016-4620. Magnetic clouds are among the most geoeffective solar events capable to trigger strong magnetic storms in the terrestrial magnetosphere. However, their characteristics and those of the surrounding media are not always capable to explain their high level of geoeffectivity. From observations and simulations, we investigate here the role of the bow shock and of the magnetosheath. Conjugated observations upstream (ACE) and downstream (CLUSTER) of the bow shock show that the magnetic clouds’ magnetic structure in the magnetosheath can strongly depart from their pristine structure upstream of the bow shock. This modification depends on the shock configuration (quasi-perpendicular, quasi-parallel). We also discuss this question from hybrid simulations of the interaction of magnetic clouds with the bow shock. We show that this interaction may produce unexpected characteristics in the magnetosheath, such as asymmetric distributions of magnetic field, density, temperature, velocity. They thus lead to interactions with the magnetosphere which were not expected from the pristine characteristics of the magnetic clouds in the solar wind upstream of bow shock. We here discuss the effects of such an asymmetric magnetosheath on key parameters for the interaction with the magnetopause (reconnection, instabilities), responsible in turn for the development of geomagnetic activity inside the magnetosphere.
• The Search-coil Magnetometer for the THOR mission
  
  • Sahraoui Fouad
  • Pinçon J.-L.
  • Jannet Guillaume
  • Mansour Malik
  • Henri Pierre
  • Chalumeau Gilles
  • Hachemi Tedjani
  • Jeandet A.
  • Briand Nicolas
  • Le Contel Olivier
  • Rezeau Laurence
  , 2016, 18, pp.EPSC2016-14239. Turbulence Heating ObserveR (THOR) is the first mission ever flown in space fully dedicated to plasma turbulence. The search-coil magnetometer (SCM) of THOR is a triaxial dual-band antenna dedicated to measuring the magnetic field fluctuations in the frequency range [1Hz,4kHz] and [1,200]kHz. THOR/SCM has a long heritage from earlier space missions such as Cluster, Themis, MMS, BepiColombo, Taranis, Solar orbiter and Solar Probe. In comparison to those missions, the SCM of THOR has a higher sensitivity level, which makes it capable of measuring very low amplitude magnetic fluctuations, in particular in the solar wind. Those measurements are crucial to address the problem of turbulence and energy dissipation at electron scales, a central goal of the THOR mission.
• Magnetic clouds in the Earth's magnetosheath: a statistical study
  
  • Turc Lucile
  • Fontaine Dominique
  • Kilpua E. K. J.
  • Escoubet P.
  , 2016, 18, pp.EPSC2016-6130. Magnetic clouds (MCs) are highly geoeffective solar wind transients. In the interplanetary space, they possess a well-defined magnetic structure, characterised by an enhanced and smoothly rotating magnetic field. We examine here whether their magnetic structure is modified when they encounter the outer regions of the geospace, namely the bow shock and the magnetosheath. Significant changes in the magnetic structure of MCs could in turn affect the level of geomagnetic activity they induce in the near-Earth's space. In this work, we study 82 MCs during which spacecraft observations are available simultaneously in the solar wind and in the magnetosheath. The observations inside the magnetosheath are related to the bow shock properties using a magnetosheath model (Turc et al., 2014, Ann. Geophys.). We find that the variation of an MC's magnetic field orientation from the solar wind to the magnetosheath is directly related to the encountered shock configuration. The angle between the magnetic field in the magnetosheath and that in the solar wind shows a very good correlation with the ThetaBn angle (between the upstream magnetic field and the normal to the shock's surface) encountered at the bow shock's crossing. Because of its importance for the geoeffectivity, we examine how the magnetic field North-South (Bz) component is modified across the bow shock. In some cases, we find that Bz reverses in the magnetosheath. The conditions during which such reversals occur are investigated and their implications in terms of the MCs' geoeffectivity are discussed.
• Alfvén-dynamo balance and magnetic excess in MHD turbulence
  
  • Grappin Roland
  • Müller Wolf-Christian
  • Verdini Andrea
  , 2016, 18, pp.EPSC2016-8978. - - 3D Magnetohydrodynamic (MHD) turbulent flows with initially magnetic and kinetic energies at equipartition spontaneously develop a magnetic excess (or residual energy), as well in numerical simulations and in the solar wind. Closure equations obtained in 1983 describe the residual spectrum as being produced by a dynamo source proportional to the total energy spectrum, balanced by a linear Alfvén damping term. A good agreement was found in 2005 with incompressible simulations; however, recent solar wind measurements disagree with these results. The previous dynamo-Alfvén theory is generalized to a family of models, leading to simple relations between residual and total energy spectra. We want to assess these models in detail against MHD simulations and solar wind data. The family of models is tested against compressible decaying MHD simulations with low Mach number, zero cross-helicity, zero mean magnetic field, without or with expansion terms (EBM or expanding box model). A single dynamo-Alfvén model is found to describe correctly both solar wind scalings and compressible simulations without or with expansion. It is equivalent to the 1983-2005 closure equation but with critical balance of nonlinear turnover and linear Alfvén times, while the dynamo source term remains unchanged. The discrepancy with previous incompressible simulations is elucidated. The model predicts a linear relation between the spectral slopes of total and residual energies mR = -1/2 3/2mT. Examining the solar wind data as in [?], our relation is found to be valid whatever the cross-helicity, even better so at high cross-helicity, with the total energy slope varying from 1.7 to 1.55. - -
• PC spectral analysis of L-shell copper X-pinch plasma produced by the compact generator of Ecole polytechnique
  
  • Yilmaz M. F.
  • Danisman Y.
  • Larour Jean
  • Arantchouk Léonid
  , 2017, 1811, pp.060002. High Energy Density Physics session oral presentation refered article Principal Component Analysis (PCA) is applied and compared with the line ratios of special Ne-like transitions for investigating the electron beam effects on the L-shell Cu synthetic spectra. The Principal Components (PC) of L-shell Cu are extracted over a non-LTE collisional radiative L-shell Cu model with and without presence of hot electrons to discuss the electron beam effects. Furthermore, PC spectra of Ne-like transitions are also studied as an alternative diagnostics to investigate the polarization sensitivity of these transtions. The extracted PCs are used to estimate the plasma electron temperature, density and beam fractions from a representative time-integrated spatially-resolved L-shell Cu X-pinch plasma spectrum. The experimental spectrum is produced by the explosion of 25-µm Cu wires on a compact L-C (40&#8197;kV, 200&#8197;kA, 200&#8197;ns) generator. The modeled plasma electron temperatures are about Te &#8764; 125eV and ne = 5×1019 cm&#8722;3 in the presence of the fraction of the beams with f &#8764; 0.05 and centered energy of &#8764;10 keV. (10.1063/1.4975726)
  DOI : 10.1063/1.4975726
• Prolongation of the lifetime of guided discharges triggered in atmospheric air by femtosecond laser filaments up to 130 μs
  
  • Arantchouk Léonid
  • Honnorat Bruno
  • Thouin Emmanuelle
  • Point Guillaume
  • Mysyrowicz A.
  • Houard Aurélien
  Applied Physics Letters, American Institute of Physics, 2016, 108 (17), pp.173501. The triggering and guiding of electric discharges produced in atmospheric air by a compact 100 kV Marx generator is realized in laboratory using an intense femtosecond laser pulse undergoing filamentation. We describe here an approach allowing extending the lifetime of the discharges by injecting a current with an additional circuit. Laser guiding discharges with a length of 8.5 cm and duration of 130 μs were obtained. (10.1063/1.4947273)
  DOI : 10.1063/1.4947273
• Modeling of the L-shell copper X-pinch plasma produced by the compact generator of Ecole polytechnique using pattern recognition
  
  • Larour Jean
  • Arantchouk Léonid
  • Danisman Yusuf
  • Eleyan Alaa
  • Yilmaz Mehmet Fatih
  Physics of Plasmas, American Institute of Physics, 2016, 23 (03), pp.033115. Principal component analysis is applied and compared with the line ratios of special Ne-like transitions for investigating the electron beam effects on the L-shell Cu synthetic spectra. The database for the principal component extraction is created over a non Local Thermodynamic Equilibrium (non-LTE) collisional radiative L-shell Copper model. The extracted principal components are used as a database for Artificial Neural Network in order to estimate the plasma electron temperature density and beam fractions from a representative time-integrated spatially resolved L-shell Cu X-pinch plasma spectrum. The spectrum is produced by the explosion of 25-μm Cu wires on a compact LC (40 kV 200 kA and 200 ns) generator. The modeled plasma electron temperatures are about Te ∼ 150 eV and Ne = 5 × 1019 cm−3 in the presence of the fraction of the beams with f ∼ 0.05 and a centered energy of ∼10 keV. (10.1063/1.4943874)
  DOI : 10.1063/1.4943874
• La mission THOR (Turbulence Heating ObserveR)
  
  • Sahraoui Fouad
  , 2016.
• Double beam satellite propulsion
  
  • Aanesland Ane
  • Rafalskyi D.V.
  , 2016.
• Un site web pour parcourir les aperçus des données de l'instrument SCM et une base miroir des données de la mission MMS
  
  • Mirioni Laurent
  • Le Contel Olivier
  • Marsac Nicolas
  , 2016. Les Search Coil Magnetometers (SCM) de chacun des 4 satellites MMS sont en fonctionnement depuis le lancement de la mission en mars 2015 acquérant chaque jour autour dun gigaoctet de données par satellite (en mode survey, burst et high burst). Il est important pour le LPP de se doter d'un outil de visualisation rapide de ces données afin de surveiller le fonctionnement de linstrument et de détecter déventuelles anomalies via notamment lanalyse des calibrations en vol qui sont effectuées au moins une fois par orbite. Cet outil, est actuellement en développement au LPP. Il permettra également aux scientifiques de sélectionner les données en identifiant des évènements intéressants, puis de télécharger directement le fichier de données via la base miroir locale, ainsi que les aperçus associés (position de la constellation, quicklook fields). Le volume imposant des données (> 10To/an) rend en effet pertinentes la construction et la gestion dune base miroir locale incluant les données SCM mais également les données calibrées (L2) des autres instruments afin de permettre aux scientifiques de diminuer les temps de transfert de ces données très volumineuses et de réaliser des études statistiques sur des grands ensembles de données. Cest cette base qui, par exemple, devrait alimenter les projets de machine-learning en cours de développement au LPP.
• Premiers résultats de la mission Magnetospheric Multiscale
  
  • Le Contel Olivier
  • Retinò Alessandro
  • Breuillard Hugo
  • Berthomier Matthieu
  • Mirioni Laurent
  • Chust Thomas
  • Chasapis A.
  • Aunai N.
  • Lavraud Benoit
  • Jacquey C.
  • Vernisse Yoan
  , 2016.
• Middle and low latitude ionosphere response to 2015 St. Patrick's Day geomagnetic storm
  
  • Nava B.
  • Rodríguez-Zuluaga J.
  • Alazo-Cuartas K.
  • Kashcheyev A.
  • Migoya-Orué Y.
  • Radicella S.M.
  • Amory-Mazaudier Christine
  • Fleury Rolland
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2016. This paper presents a study of the St Patrick's Day storm of 2015, with its ionospheric response at middle and low latitudes. The effects of the storm in each longitudinal sector (Asian, African, American, and Pacific) are characterized using global and regional electron content. At the beginning of the storm, one or two ionospheric positive storm effects are observed depending on the longitudinal zones. After the main phase of the storm, a strong decrease in ionization is observed at all longitudes, lasting several days. The American region exhibits the most remarkable increase in vertical total electron content (vTEC), while in the Asian sector, the largest decrease in vTEC is observed. At low latitudes, using spectral analysis, we were able to separate the effects of the prompt penetration of the magnetospheric convection electric field (PPEF) and of the disturbance dynamo electric field (DDEF) on the basis of ground magnetic data. Concerning the PPEF, Earth's magnetic field oscillations occur simultaneously in the Asian, African, and American sectors, during southward magnetization of the B z component of the interplanetary magnetic field. Concerning the DDEF, diurnal magnetic oscillations in the horizontal component H of the Earth's magnetic field exhibit a behavior that is opposed to the regular one. These diurnal oscillations are recognized to last several days in all longitudinal sectors. The observational data obtained by all sensors used in the present paper can be interpreted on the basis of existing theoretical models. (10.1002/2015JA022299)
  DOI : 10.1002/2015JA022299
• Experimental investigation of the relation between H− negative ion density and Lyman-α emission intensity in a microwave discharge
  
  • Aleiferis S.
  • Tarvainen O.
  • Svarnas P.
  • Bacal M.
  • Béchu Stéphane
  Journal of Physics D: Applied Physics, IOP Publishing, 2016, 49 (9), pp.095203. A new mechanism for producing negative ions in low density and low power hydrogen plasmas was proposed recently. It refers to anion formation due to collisions between hydrogen atoms being in the first excited state. The proposed mechanism was indirectly supported by the quadratic relation observed between the extracted negative ion current and Lyman-α radiation of a filament-driven arc discharge, when borrowed data from the literature were combined. The present work provides experimental data comparing directly the absolute negative ion density and Lyman-α radiation in an ECR-driven hydrogen plasma source. The previously mentioned quadratic relation is not observed in the specific source studied, underlying the difficulty of distinguishing between the proposed mechanism and other negative ion production paths. (10.1088/0022-3727/49/9/095203)
  DOI : 10.1088/0022-3727/49/9/095203
• Surface monitoring for understanding plasma-catalyst coupling: fundamentals to process
  
  • Rousseau Antoine
  , 2016.
• Long-lived plasma and peculiarities of N2(C3Piu) quenching in nitrogen excited by pulsed nanosecond discharge at high specific deposited energy
  
  • Lepikhin N D
  • Popov N A
  • Starikovskaia Svetlana
  , 2016.
• Optimum plasma grid bias for a negative hydrogen ion source operation with Cs
  
  • Bacal M.
  • Sasao Mamiko
  • Wada Motoi
  • Mcadams Roy
  Review of Scientific Instruments, American Institute of Physics, 2016, 87 (2), pp.02B132. The functions of a biased plasma grid of a negative hydrogen (H−) ion source for both pure volume and Cs seeded operations are reexamined. Proper control of the plasma grid bias in pure volume sources yields: enhancement of the extracted negative ion current, reduction of the co-extracted electron current, flattening of the spatial distribution of plasma potential across the filter magnetic field, change in recycling from hydrogen atomic/molecular ions to atomic/molecular neutrals, and enhanced concentration of H− ions near the plasma grid. These functions are maintained in the sources seeded with Cs with additional direct emission of negative ions under positive ion and neutral hydrogen bombardment onto the plasma electrode. (10.1063/1.4935007)
  DOI : 10.1063/1.4935007
• THOR: a candidate ESA mission to explore turbulent energy dissipation and particle energization in space plasmas
  
  • Retinò Alessandro
  , 2016.