Publications

2016

• 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.
• 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.
• 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. - -
• New observations of flux ropes in the magnetotail reconnection region
  
  • Huang S. Y.
  • Retinò Alessandro
  • Phan T. D.
  • Daughton W. Bill
  • Vaivads A.
  • Karimabadi H.
  • Pang Y.
  • Zhou M.
  • Sahraoui Fouad
  • Li G. L.
  • Yuan Z. G.
  • Deng X. H.
  • Fu H.S.
  • Fu S. Y.
  • Wang D. D.
  , 2016, 18, pp.EPSC2016-7122. Magnetic reconnection is a fundamental physical process that enables the rapid transfer of magnetic energy into plasma kinetic and thermal energy in the laboratory, astrophysical and space plasma. Flux ropes have been suggested to play important role in controlling the micro-scale physics of magnetic reconnection and electron acceleration. In this presentation, we report new observations of flux ropes in the magnetotail reconnection region based on the Cluster multi-spacecraft data. Firstly, two consecutive magnetic flux ropes, separated by less than 30 s (Deltat < 30 s), are observed within one magnetic reconnection diffusion region without strong guide field. In spite of the small but non-trivial global scale negative guide field (-By), there exists a directional change of the core fields of two flux ropes, i.e. -By for the first one, and By for the second one. This is inconsistent with any theory and simulations. Therefore, we suggest that the core field of flux ropes is formed by compression of the local preexisting By, and that the directional change of core field is due to the change of local preexisting By. Such a change in ambientBy might be caused by some microscale physics. Secondary, we will present in-situ observations of a small scale flux rope locally formed at the separatrix region of magnetic reconnection without large guide field. Bidirectional electron beams (cold and hot beams) and density cavity accompanied by intense wave activities substantiate the crossing of the separatrix region. Density compression and one parallel electron beam are detected inside the flux rope. We suggest that this flux rope is locally generated at the separatrix region due to the tearing instability within the separatrix current layer. This observation sheds new light on the 3D picture of magnetic reconnection in space plasma.
• The physics of magnetic reconnection onset at the subsolar magnetopause: MMS observations
  
  • Retinò Alessandro
  , 2016, 18, pp.EPSC2016-15763. Magnetic reconnection is a fundamental process occurring in thin current sheets where a change in the magnetic field topology leads to fast magnetic energy conversion into charged particles energy. A key yet poorly understood aspect is how reconnection is initiated in the diffusion region by microphysical processes occurring at electron scales, the so-called onset problem. Reconnection onset leads to the energization of particles around reconnection sites, yet the exact energization mechanisms are also not yet fully understood. Simulations have provided some suggestions on the mechanisms responsible for onset and particle energization, however direct observations have been scarce so far. The four-spacecraft Magnetospheric Multiscale Mission (NASA/MMS) has been launched in March 2015 and allows, for the first time, in-situ observations of reconnection diffusion regions with adequate resolution to study electron scales. Here we present MMS observations in diffusion regions at the subsolar magnetopause and we investigate the conditions for reconnection onset. We select a few events with multiple crossings of the magnetopause current sheet for which signatures of absence of reconnection are rapidly followed by signatures of reconnection, and compare the measured electric field with the electric field due to both kinetic effects (electron pressure tensor, electron inertia terms) and to anomalous resistivity associated to different wave modes (e.g. lower hybrid waves, whistler waves, etc.). We also analyze electron distribution functions to study the mechanisms of electron energization in the diffusion region.
• Does the plasma radiate near a Double Layer?
  
  • Pottelette Raymond
  • Berthomier Matthieu
  • Pickett J. S.
  , 2016, 18, pp.EPSC2016-3017. Earth is an intense radio source in the kilometer wavelength range. Being a direct consequence of the parallel acceleration processes taking place in the Earth's auroral region, the radiation contains fundamental information on the characteristic spatial and temporal scales of the turbulent accelerating layer. It is now widely assumed that the cyclotron maser instability leads to Auroral Kilometric Radiation (AKR) generation. It has been suggested from the FAST measurements that the AKR results from a so-called horseshoe electron distribution. This distribution is generated when a localized parallel electric field - called Double Layer (DL) - accelerates earthward the electrons that propagate into an increasing magnetic field. The magnetic moment of the electrons is conserved so that their pitch angle is increased. This results in the creation of a horseshoe-like shape for the electron distribution exhibiting large positive velocity gradients in the direction perpendicular to B, thereby providing free energy for the AKR generation which takes place at the local electron gyrofrequency. In these circumstances, the radiation is generated far away (several thousand kilometers) from a DL, because the parallel accelerated electrons need to travel a long distance before forming a horseshoe distribution. From an experimental point of view, it is not an easy task to highlight the presence of DLs, because they are moving transient structures so that high time resolution measurements are needed. A detailed analysis suggests that these large-amplitude parallel electric fields are located inside sharp density gradients at the interface separating the cold, dense ionospheric plasma from the hot, tenuous magnetospheric plasma. We present some FAST observations which illustrate the generation of elementary radiation events in the neighborhood of a DL. The events occur 10 to 20% above the local electron gyrofrequency in association with the presence of nonlinear coherent structures (such as electron holes) located on the high potential side of the DL. These observational results might encourage investigation of such radiating processes because they could be relevant to other astrophysical radio sources, such as the recently discovered aurora around a brown dwarf.
• Coexistence of weak and strong wave turbulence in incompressible Hall MHD
  
  • Meyrand Romain
  • Kiyani K. H.
  • Galtier Sébastien
  , 2016, 18, pp.EPSC2016-18282. We report a numerical investigation of 3D Hall Magnetohydrodynamic turbulence with a strong mean magnetic field. By using a helicity decomposition and a cross-bicoherence analysis, we observe that the nonlinear 3-wave coupling is substantial among ion cyclotron and whistler waves. By studying in detail the degree of nonlinearity of these two populations we show that ion cyclotron and whistler turbulent fluctuations belong respectively to strong and weak wave turbulence. The non trivial blending of these two regime give rise to anomalous anisotropy and scaling properties. The separation of the weak random wave and strong coherent turbulence component can however be effectively done using simultaneous space and time Fourier transforms. Using this techniques we show that it is possible to recover some statistical prediction of weak turbulent theory.
• Electromagnetic wave activity detected by MMS at the vicinity of the magnetopause and its relation to heating and acceleration of particles
  
  • Le Contel Olivier
  • Retinò Alessandro
  • Breuillard Hugo
  • Berthomier Matthieu
  • Mirioni Laurent
  • Sahraoui Fouad
  • Chust Thomas
  • Chasapis A.
  • Aunai N.
  • Lavraud Benoit
  • Lindqvist Per-Arne
  • Khotyaintsev Y. V.
  • Vaivads A.
  • Marklund Goran
  • Ergun Robert E.
  • Goodrich Katherine
  • Wilder Frederick D.
  • Argall Matthew
  • Burch Jim L.
  • Torbert Roy B.
  , 2016, 18, pp.12674. In the present study, we analyze different dayside magnetopause crossings detected by the MMS mission in order to investigate the relation between the electromagnetic wave activity and particle heating/acceleration. In particular, our study is focused on two different frequency ranges: (1) 1-10 Hz range which corresponds to the frequency domain of kinetic Alfvén and lower-hybrid waves, (2) 10 Hz-1kHz which corresponds mainly to the whistler mode wave frequency domain. After characterizing the different types of waves, we estimate their respective energy content as well as their possible role for heating and accelerating the plasma.
• Turbulent reconnection and associated particle heating and acceleration in the Earth's magnetosheath
  
  • Chasapis A.
  • Retinò Alessandro
  • Le Contel Olivier
  • Matthaeus W. H.
  • Breuillard Hugo
  • Sahraoui Fouad
  • Vaivads A.
  • Khotyaintsev Y. V.
  • Burch Jim
  • Moore Tom
  • Fuselier Stephen
  • Torbert Roy
  • Mauk Barry
  • Pollock Craig
  • Torkar Klaus
  • Ergun Robert
  , 2016, 18, pp.16046. Magnetic reconnection is a fundamental mechanism of energy dissipation and particle energization in space plasma. Spacecraft observations and numerical studies have established that it occurs in small-scale intermittent structures such as thin current sheets that form spontaneously in turbulent plasma. This kind of turbulent reconnection leads to significant particle heating and acceleration as well as to the dissipation of turbulent energy at kinetic scales. However, the extent of its contribution to turbulent dissipation has yet to be determined. Here we present results from in situ observations made by MMS and CLUSTER in the Earth's magnetosheath. A statistical study of a large number of thin current sheets allows us to establilsh their importance for dissipation while the in-depth study of reconnecting current sheets yields valuable insight into the exact mechanisms of particle heating and acceleration.
• New Observations of Solar Wind Interaction with Earth's Bow Shock
  
  • Parks G. K.
  • Lee E.
  • Yang Z. W.
  • Liu Y.
  • Fu Suiyan
  • Dandouras Iannis
  • Rème H.
  • Canu Patrick
  • Goldstein M. L.
  , 2016, 18, pp.2380. The mass, charge and energy dependence of the SW interaction with the bow shock was studied from early days of HEOS-1 and ISEE (Formisano et al, 1970; Peterson et al., 1979). These observations have shown that while thermalization of H occurs across the boundary, sometimes the SW He ions are found with unchanged energy spectra downstream of the shock inside the magnetosheath and that both SW H and He beams could be found in the downstream magnetosheath with the same bulk velocities. These studies however used He data accumulated over 30 minutes and since the SW dynamics include much faster time variations the results are likely affected by spatial and temporal variations. Moreover, it was not known at that time that the plasma in the neighborhood of the bow shock often include the reflected, gyrating and particles leaking out of the magnetosheath (Skopke et al., 1982; Thomsen et al., 1985) and since these particles occupy different parts of the velocity space, they can significantly affect the SW velocity and temperature computed from first and second velocity moments. To alleviate these problems, a microprocessor-controlled SW plasma experiment was designed and flown on Cluster that selects only particles near the peak energy of the SW distribution, thereby minimizing contamination from the other particles (Rème et al., 2001). We have studied ~110 shock crossings upstream and downstream of the quasi-perpendicular and quasi-parallel bow shock regions and find that in 44 cases the SW beams crossed the shock retaining much of their upstream features. On average the temperature of upstream SW H ions was ~4 eV and in the magnetosheath ~4.2 eV, indicating there was little or no heating of the SW going across the bow. The He ions have temperatures typically 4 times that of H ions in the SW a value consistent with equipartition of energy. Unlike H ions, He ions very often do not slow down going across the shock. These observations indicate that the SW interaction with the bow shock is much more complicated than existing models predict and they are important constraints for developing new models.
• 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
• 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.
• Double beam satellite propulsion
  
  • Aanesland Ane
  • Rafalskyi D.V.
  , 2016.
• 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.
• La mission THOR (Turbulence Heating ObserveR)
  
  • Sahraoui Fouad
  , 2016.
• 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
• 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
• 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.