Publications

2013

• Angular momentum transport modeling: achievements of a gyrokinetic quasi-linear approach
  
  • Cottier P.
  • Bourdelle C.
  • Camenen Y.
  • Gürcan Özgür D.
  • Casson F.J.
  • Garbet Xavier
  • Hennequin P.
  • Tala T.
  Plasma Physics and Controlled Fusion, IOP Publishing, 2013, 56, pp.015011. QuaLiKiz, a model based on a local gyrokinetic eigenvalue solver is expanded to include momentum flux modeling in addition to heat and particle fluxes. Essential for accurate momentum flux predictions, the parallel asymmetrization of the eigenfunctions is successfully recovered by an analytical fluid model. This is tested against self-consistent gyrokinetic calculations and allows for a correct prediction of the E×B shear impact on the saturated potential amplitude by means of a mixing length rule. Hence, the effect of the E×B shear is recovered on all the transport channels including the induced residual stress. Including these additions, QuaLiKiz remains ∼10 000 faster than non-linear gyrokinetic codes allowing for comparisons with experiments without resorting to high performance computing. The example is given of momentum pinch calculations in NBI modulation experiments. (10.1088/0741-3335/56/1/015011)
  DOI : 10.1088/0741-3335/56/1/015011
• Diagnostics of inductively-coupled plasmas in hydrogen bromide : Bromine atom and electron densities
  
  • Booth Jean-Paul
  • Sirse Nishant
  • Chabert Pascal
  • Foucher Mickaël
  , 2013.
• Impacts of Solar Wind Ions on Mercury from Global Hybrid Simulations
  
  • Chanteur Gérard
  • Modolo Ronan
  • Hess Sebastien
  • Leblanc François
  • Richer Emilie
  , 2013, 13, pp.P13A-1729. In 1974 Mariner-10 discovered the hermean magnetosphere characterized by its smallness and the proximity of the bow shock and magnetopause to the surface of the planet. More than thirty years later MESSENGER orbital observations revealed an important quadrupolar component of the internal magnetic field of Mercury. It has long been suspected since Mariner-10 observations that solar wind ions could reach the surface of the planet and many numerical simulations and theoretical studies using various models have presented maps of precipitating proton fluxes. Attempts to refine these predictions of precipitating fluxes of solar wind ions are important as these precipitations create additional sources of exospheric populations and as their space-weathering effects modify the properties of the regolith. We run the global hybrid model used by Richer et al. (2012) which takes self-consistently into account the alpha particles of the solar wind to estimate fluxes of solar wind protons and alphas impacting the surface of Mercury under different IMF conditions. The internal source of the hermean magnetic field is axisymmetric and is the superposition of a dipole and a quadrupole consistent with MESSENGER observations as in Richer et al. 2012. These simulations, made with an improved spatial resolution, reveal important differences between proton and alpha fluxes mainly due to the different magnetic rigidities of these particles. Reference Richer, E., R. Modolo, G. M. Chanteur, S. Hess, and F. Leblanc (2012), A global hybrid model for Mercury's interaction with the solar wind: Case study of the dipole representation, J. Geophys. Res., 117, A10228, doi:10.1029/2012JA017898.
• Quantified Energy Dissipation Rates in the Terrestrial Bow Shock
  
  • Wilson L B
  • Sibeck David G.
  • Breneman A. W.
  • Le Contel Olivier
  • Cully C. M.
  • Turner D. L.
  • Angelopoulos V.
  • Malaspina D.
  , 2013, pp.SM31A-2107. We present the first observationally quantified measure of the energy dissipation rate due to wave-particle interactions in the transition region of the Earth's collisionless bow shock using data from the THEMIS spacecraft. Each of more than 11 bow shock crossings examined with available wave burst data showed both low frequency (<10 Hz) magnetosonic-whistler waves and high frequency (&#8805;10 Hz) electromagnetic and electrostatic waves throughout the entire transition region and into the magnetosheath. The high frequency waves were identified as combinations of ion-acoustic waves, electron cyclotron drift instability driven waves, electrostatic solitary waves, and electromagnetic whistler mode waves. These waves were found to have: (1) amplitudes capable of exceeding &#948;B ~ 10 nT and &#948;E ~ 300 mV/m, though more typical values were &#948;B ~ 0.1-1.0 nT and &#948;E ~ 10-50 mV/m; (2) energy fluxes in excess of 2000 &#956;W m&#8722;2; (3) resistivities > 9000 &#937; m; and (4) energy dissipation rates > 3 &#956;W m&#8722;3. The high frequency (>10 Hz) electromagnetic waves produce such excessive energy dissipation that they need only be, at times, < 0.01% efficient to produce the observed increase in entropy across the shocks necessary to balance the nonlinear wave steepening that produces the shocks. These results show that wave-particle interactions have the capacity to regulate the global structure and dominate the energy dissipation of collisionless shocks.
• Do Hot Flow Anomalies Cause Dramatic Effects on the Entire Magnetosphere?
  
  • Parks G. K.
  • Lee E.
  • Fu S. Y.
  • Lin N.
  • Hong J.
  • Rème H.
  • Dandouras I. S.
  • Canu Patrick
  • Cao J.B.
  • Goldstein M. L.
  • Liu Y. D.
  • Shi J. K.
  , 2013, 13, pp.SM13C-02. Hot flow anomalies (HFAs) are nonlinear structures upstream of Earth's bow shock. Two important properties associated with HFAs are (1) the solar wind (SW) mean flow slows down and deviates substantially and (2) the temperature of the plasma increases in the structure. To understand what could cause these two feffects, the Cluster plasma ion experiment was reconfigured in 2010 and 2011 to sample 3D distributions of the SW and backstreaming particles with spin period time resolution (4s). The new data show the SW beam in HFAs is persistent and the slowdown and deviation of the bulk flow is due to reflected particles canceling the SW beam when computing moments. Data show the SW beam is present throughout the entire HFA event maintaining a nearly constant beam velocity and temperature. Our observations are not consistent with the suggestion that HFAs can cause dramatic effects on the entire magnetosphere driving large variations in the motion and location of the magnetopause.
• VLF saucers source region and generation revealed by the four Cluster satellites
  
  • Masson A.
  • Berthomier Matthieu
  • Pickett J. S.
  • Fazakerley A.
  • Forsyth C.
  • Escoubet C. Philippe
  • Laakso H. E.
  • Rauch J.-L.
  • Décréau Pierrette
  , 2013, 11, pp.SM11B-2103. A VLF saucer is a natural radio-wave phenomenon observed in the auroral zone since the 1960's. It has a characteristic V-shaped signature on electric field spectrograms in the VLF range. Many properties of VLF saucers have been established in the 1970's based on Alouette and Isis spacecraft. Further investigations continued thanks to satellites flying over the auroral zone, such as Viking, Polar and FAST. Since 2006, the orbits of the ESA/NASA Cluster satellites are slowly evolving from a nominal polar orbit to an oblique one. Meanwhile, the perigee of their orbits, originally at 19,000 km, naturally decreased to a few hundred kilometres and since 2011 have been steadily increasing back to the original perigee. Since spring 2009, Cluster scientists can make use of this natural orbital drift to target a new key region of the magnetosphere: the Auroral Acceleration Region (AAR). The AAR continues to be targeted by the Cluster mission, with a recent data campaign achieved successfully in Spring 2013. On rare occasions, VLF saucers are observed by the Cluster spacecraft, as they need to fly close enough to their source to catch them. Unique observations of electrostatic VLF saucers by the four Cluster satellites will be presented. These data not only enable for the first time to triangulate their source region, but they also allow revisiting some of the hypotheses commonly used so far in the analysis of their source region. Finally, the multi-point observations of VLF saucers question fundamental aspects of their generation. Indeed, it is difficult to understand, based on previously published studies, how transient structures such as electron holes are able to support the continuous generation of these electrostatic waves during several minutes, as observed by Cluster.
• Formation of dipolarization fronts inside reconnection diffusion region
  
  • André M.
  • Retinò Alessandro
  • Huang S. Y.
  • Fu H.
  • Khotyaintsev Y. V.
  • Cao J.B.
  • Sitnov M. I.
  • Runov A.
  • Fu S. Y.
  • Hamrin M.
  , 2013, 13, pp.SM13B-2159. For the first time, dipolarization fronts (DFs) are observed inside reconnection diffusion region, where the obstruction of reconnection jets by pre-existing plasmas is very weak. Also observed are whistlers at the DFs and magnetic island near the X-line. We find that the whistlers at the Earthward DF are much intenser than the whistlers at the tailward DF, as the electron temperature at the Earthward DF is more anisotropic (T&#8869; > T//). This observation provides the first in situ evidence of previous simulation results that DFs can be produced by transient reconnection. We also discuss other generation mechanisms of DFs in this letter. The discovery of DFs inside reconnection diffusion region is important because the DF structure may provide a favorable condition for accelerating suprathermal electrons there.
• Systematic measurements of propagation parameters of whistler-mode waves in the outer Van Allen belt: first results from the Van Allen probes compared to the database from the Cluster mission
  
  • Santolík O.
  • Hospodarsky G. B.
  • Kurth W. S.
  • Averkamp T. F.
  • Kletzing C.
  • Cornilleau-Wehrlin Nicole
  , 2013, 31, pp.SM31B-06. Electron populations of different energies in the Van Allen radiation belts can be influenced by whistler-mode waves. For example, these waves can cause pitch-angle and/or energy diffusion. They can therefore contribute to losses and local acceleration of radiation belt electrons. Wave propagation directions are a crucial parameter of the underlying wave-particle interactions. We use new measurements of whistler-mode waves by the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) onboard the Van Allen Probes spacecraft. Multicomponent data recorded and processed by this instrument allow us to systematically estimate the wave propagation parameters. We use the survey data from the first year of operations of the EMFISIS instrument to determine probability density functions of propagation characteristics of whistler-mode waves. We compare these results with a large database of measurements of the STAFF-SA instrument onboard the Cluster spacecraft, covering a time interval of more than one solar cycle. This work receives EU support through the FP7-Space grant agreement no 284520 for the MAARBLE collaborative research project.
• Observations of Thin Current Sheets in the Solar Wind and Their Role in Magnetic Energy Dissipation
  
  • Perri S.
  • Goldstein M. L.
  • Dorelli J. C.
  • Sahraoui Fouad
  • Gurgiolo C. A.
  • Karimabadi H.
  • Mozer F.
  • Wendel D. E.
  • Tenbarge J.
  • Roytershteyn V.
  , 2013, 51, pp.SH51B-2099. A recent analysis of 450 vec/s resolution data from the STAFF search-coil magnetometer on board Cluster has revealed, for the first time, the presence of thin current sheets and discontinuities from the proton Larmor scale down to the electron Larmor scale in the solar wind. This is in the range of scales where a cascade of energy consistent with highly oblique kinetic Alfvénic fluctuations (KAW), eventually dissipated by electron Landau damping, has been detected. The current sheets have been found to have a size between 20-200 km, indicating that they are very localized. We will compare the observations with results coming from 2D Hall MHD, Gyrokinetic, and full Particle-in-Cell turbulence simulations. Preliminary work has highlighted promising qualitative agreement between the properties of the structures observed in the Cluster data and the current sheets generated in the simulations. With the aim of investigating the role played by those structures in dissipating the magnetic energy in the solar wind, E&#9679;J has been computed within each magnetic discontinuity. This has been made possible via a combined analysis of both STAFF-SC magnetic field data and the electric field data from the Electric Fields and Wave instrument (EFW). We describe procedures used to reduce the noise in the EFW data. The results obtained represent an effort to clarify the processes involved in the dissipation of magnetic energy in the solar wind.
• Cluster Inner Magnetosphere Campaign: Multispacecraft Observations of Equatorial Magnetosonic Waves
  
  • Walker S. N.
  • Balikhin M. A.
  • Yearby K. H.
  • Canu Patrick
  • Pickett J. S.
  • Christopher I.
  • Eriksson A. I.
  • Santolík O.
  • Fazakerley A.
  • Dandouras I. S.
  • Pokhotelov O. A.
  • Escoubet C. Philippe
  • Carr C. M.
  , 2013, 43, pp.SM43A-2271. The main target of the Cluster inner magnetosphere campaign (July-October 2013) is to identify linear and nonlinear processes that affect EMIC, equatorial magnetosonic and chorus waves. The present study examines equatorial magnetosonic waves that are regularly observed under the arch of the plasmasphere, due to the formation of a natural waveguide like structure. These waves are usually observed in the frequency range from a few tens to hundreds of Hz. The spectrum exhibits a banded structure whose spacing is of the order of the ion gyrofrequency in the source region. This fine structure results in complications for the identification of the wave dispersion using data from multispacecraft separated by distances of around 10-100 km. It is shown how this complication can be resolved. The resulting dispersion of the observed waves is presented and compared with analytical solutions.
• Cluster multi-spacecraft observations of electron and ion holes in the Auroral Acceleration Region
  
  • Fazakerley A.
  • Pickett J. S.
  • Berthomier Matthieu
  • Mutel R. L.
  • Masson A.
  • Forsyth C.
  • Owen C. J.
  • Khotyaintsev Y. V.
  • André M.
  • Carr C. M.
  , 2013, 14, pp.SM14B-04. In spring 2013, the Cluster spacecraft have visited the Auroral Acceleration Region (AAR) for the second and final time. The spacecraft constellation was arranged to produce very small separation magnetic field aligned conjunctions (~10s km) between C3 and C4, with C1 relatively nearby. The goal was to allow study of electron and ion holes, including their propagation between C3 and C4, and their roles in generating waves that may be observed locally and also at C1. Detailed planning work has tried to maximize the opportunities to use the Cluster payload effectively during these conjunctions, but the presence of auroral activity during the relatively few AAR passes cannot be guaranteed in advance. The dataset may also be valuable for other aspects of auroral science, as data is collected throughout the AAR crossings, not only at the conjunctions. We intend to present first results from this campaign.
• Turbulence in Collisionless Space Plasmas: a Comparative Study Between the Solar Wind and the Magnetosheath
  
  • Sahraoui Fouad
  • Huang S. Y.
  • Goldstein M. L.
  , 2013, pp.SH51B-2100. Recent studies of kinetic scales solar wind turbulence have revealed new features of the processes of energy cascade and dissipation at electron scales. However, several instrumental limitations have been found and shown to prevent one from deducing firm conclusions about the nature of the turbulence (e.g., scaling, anisotropy) at those scales. These limitations stem in particular from the low SNR (Signal-to-Noise-Ratio) in the solar wind due to the small amplitude of the electric and magnetic field fluctuations. To overcome this difficulty, we study the turbulence in the terrestrial magnetosheath (i.e., the region of the solar wind that is downstream of the Earths bow shock), where the turbulent fluctuations become enhanced, which yields a higher SNR. We have performed a statistical study using the Cluster wave data (1Hz<fsc<180Hz), focusing particularly on the magnetic and electric field energy spectra. We discuss the properties of the magnetosheath turbulence at those scales and compare to recent published work in the solar wind and to existing theoretical predictions. We discuss the implications of the results on physical mechanisms and on the theoretical modeling of energy dissipation in collisionless plasmas.
• Titan's induced magnetosphere from plasma wave, particle data and magnetometer observations
  
  • Modolo Ronan
  • Romanelli N.
  • Canu Patrick
  • Coates A. J.
  • Berthelier Jean-Jacques
  • Bertucci C.
  • Leblanc François
  • Piberne Rodrigue
  • Edberg N. J.
  • Kurth W. S.
  • Gurnett D. A.
  • Wahlund J. E.
  , 2013, 21, pp.SM21B-2192. The Magnetometer (MAG) measurements, the particle data (CAPS) are combined with the Radio and Plasma Wave Science (RPWS) observations to provide an overall and organized description of the electron plasma environment and the pickup ion distribution around Titan. RPWS observations are used to measure the electron number density of the thermal plasma close to Titan. This data set is combined with CAPS-ELS electron number density in Saturn's magnetosphere and Titan's environment. A relatively good correspondence between the number density estimated from CAPS-ELS and RPWS are most of the time observed between 0.1 - 1 cm-3. Combining both ELS and RPWS data allows deducing a continuous electron density profile going from Saturn's magnetosphere to Titan's ionosphere leading to a global electron density map in Titan's vicinity. The MAG observations are used to derive information about the ambient magnetic field environment in the vicinity of Titan and also to emphasize the bipolar tail region. Ion information such the mass composition of the plasma and ion distribution function for specific time intervals are determined from CAPS-IMS. Pick-up ions have been identified from their energy signature and mass composition for few flybys. These observations also emphasized a ring distribution, characteristic of pick-up ions. The pick-up observations, in the DRAP coordinate system, are found to be located in the E=-vxB hemisphere as expected.
• Direct Determination of Wavenumbers of ULF Waves Using the Cluster Multipoint and Multicomponent Measurements
  
  • Grison B.
  • Escoubet C. Philippe
  • Santolík O.
  • Cornilleau-Wehrlin Nicole
  , 2013, 14, pp.SM14B-03. The wavenumber is a key parameter to understand the physics of the interactions between the electromagnetic waves and the ionized particles in space plasmas. Search-coil magnetometers and electric antennas measure time series of both magnetic and electric field fluctuations, respectively. The fleet of four Cluster spacecraft made possible to determine the full wave vector and even to differentiate the waves present at the same frequency in the spacecraft frame through various techniques: k-filtering analysis, wave telescope, phase differentiating method. However the fleet configuration (inter-spacecraft separation, tetrahedron elongation and planarity) limit the possibilities to use these techniques. From single spacecraft measurements, assumptions concerning the wave mode -and thus, concerning the physical processes- are usually required to derive the corresponding wavenumber. Using three orthogonal magnetic components and two electric antennas, it is possible to estimate n/Z where n is the refractive index and Z the transfer function of the interface between the plasma and the electric antennas. For ULF waves we assume Z=1 and we thus obtain the wavenumber. We test this hypothesis on a case where the spacecraft are in a close configuration in the distant cusp region and where we are able to apply the k-filtering analysis, too. The results obtained by multispacecraft and multicomponents analysis are close to each other and permit us to precise the value of Z. We test this procedure on several events (in various regions of the magnetosphere) in order to get more precise wave number measurements from the single spacecraft analysis. The research leading to these results has received funding from the European Community's Seventh Framework Programme (FP7-SPACE-2010-1) under grant agreement n. 284520 (MAARBLE).
• Cluster Spacecraft Observations of Magnetopause Reconnection at Multiple Scales
  
  • Retinò Alessandro
  • Vaivads A.
  • Chasapis A.
  • Rossi C.
  • Sahraoui Fouad
  • Canu Patrick
  • Nakamura R.
  • Mozer F.
  , 2013, 13, pp.SM13E-06. Magnetic reconnection is an inherently multi-scale process where the dynamics at small-scales strongly affect the large-scale evolution of the process. The microphysics of reconnection (i.e. the physics at proton scales and below) is particularly important. Key questions are reconnection onset, time evolution (rate) and ion and electron heating/acceleration around reconnection sites. The Earth's magnetopause is an excellent laboratory for studying reconnection, especially at subsolar point where is more steady and easier to study with spacecraft data. Despite of initially being a high-latitude mission, ESA/Cluster spacecraft have crossed the subsolar magnetopause starting from 2008. During such recent orbits two spacecraft were separated by ~10s km (sub-proton/electron scales) while being apart ~ 1000s km (fluid scales) from the others. This special configuration allows studying reconnection at multiple scales. Here we present a few examples of magnetopause reconnection from such recent Cluster multi-scale orbits. For one case of subsolar reconnection, the observation of jet reversals at large scales allows setting the position of the reconnection site in between the spacecraft. Two-point observations at sub-proton/electron scales are then used to identify a very thin rotational discontinuity (having a thickness of about 10 electron gyroradii) and study the microphysics therein. We also show a few other examples of magnetopause reconnection from the Cluster Guest Investigator campaign (2012), for which orbit, spacecraft configuration and instrument modes were tailored to study reconnection at multiple scales. We discuss the relevance of such recent Cluster measurements for the reconnection science of upcoming NASA/MMS and other multi-scale future missions.
• Centrifugally Stimulated Exospheric Ion Escape at Mercury
  
  • Delcourt Dominique
  • Seki K.
  • Terada N.
  • Moore T. E.
  , 2013, 12, pp.P12B-03. We investigate the escape of exospheric ions such as Na into the Hermean magnetosphere. We demonstrate that, because of small spatial scales, the centrifugal effect due to curvature of the ExB drift paths is enhanced at Mercury and that it can lead to significant (up to several hundreds of eV) Na energization in the parallel direction. We demonstrate that, because of this centrifugal effect, ions with initial speed well below the escape speed such as those produced via thermal desorption can overcome gravity and gain access to the magnetotail. We show that the escape route of this low-energy exospheric material spreads over a narrower range of altitudes when the convection rate increases and that bulk transport occurs within a limited region of space. These results suggest that, via release of planetary material that would otherwise be gravitationally trapped, the ExB related centrifugal acceleration is an important mechanism for the net supply of plasma to Mercury's magnetosphere.
• Amplitudes and frequency sweep rates of wave packets of whistler-mode chorus observed by the Cluster spacecraft
  
  • Macusova E.
  • Santolík O.
  • Pickett J. S.
  • Gurnett D. A.
  • Cornilleau-Wehrlin Nicole
  • Demekhov A. G.
  • Titova E. E.
  , 2013, 43. Whistler-mode chorus is one of the most intense electromagnetic wave emissions observed in the inner magnetosphere, usually outside the plasmasphere. These waves play an important role in wave-particle interactions. They are usually generated close to the geomagnetic equator in a wide range of L-shells, and they propagate toward larger magnetic latitudes. Whistler-mode chorus is sometimes composed of two frequency bands separated by a gap at one half of the electron cyclotron frequency. At short time scales (on the order of hundreds of milliseconds) chorus consist of different discrete spectral shapes: rising tones, falling tones, constant frequency tones, and hooks. Our survey is based on high time resolution measurements collected by the WBD instrument onboard four Cluster spacecraft. We analyze time intervals containing different types of spectral shapes occurring at different L-shells, and at different latitudes relative to the chorus source region, as it is determined from measurements of the STAFF-SA instrument. Each of these events includes a large number of individual wave packets (between a few hundreds to a few thousands). For each individual wave packet we determine the frequency sweep rate and the average amplitude. Our results confirm previous conclusions of numerical simulations, theoretical predictions, and case studies showing that the amplitude of chorus wave packets increases with an increasing frequency sweep rate. The amplitude also increases as the wave forming chorus propagate away from the equator. The scatter of obtained values of frequency sweep rates and amplitudes is much larger closer to the Earth than at larger radial distances. This work receives EU support through the FP7-Space grant agreement no 284520 for the MAARBLE collaborative research project.
• Electron non-ideal physics in asymmetric magnetic reconnection
  
  • Aunai N.
  • Hesse Michael
  • Zenitani Seiji
  • Kuznetsova M. M.
  • Black C.
  • Evans R. M.
  • Smets Roch
  , 2013, 13, pp.SM13B-2155. Magnetic reconnection is an ubiquitous phenomena enabling the transport across magnetic boundaries, while heating and accelerating plasma. These boundaries often separate plasmas with distinct origins, and therefore generally have different properties such as different densities and magnetic field amplitudes. Magnetic reconnection in these so-called asymmetric current layers is still poorly known, it is thus important to understand to what extent our previous understanding, gained from symmetric models, still applies to asymmetric configurations. In this presentation, we will show new results about reconnection in asymmetric systems, and will in particular address the role of electron kinetic physics within this context. Results are obtained from hybrid-PIC and fully kinetic PIC simulation, and discuss the modeling of non-ideal electron terms in Hybrid models, fluid versus kinetic behavior of the electrons and the way to visualize regions of non-fluid electron behavior with nongyrotropy.
• A survey study of sub-ion scale turbulent fluctuations in the solar wind - observational constraints for the 'Turbulent Dissipation Challenge
  
  • Kiyani K. H.
  • Osman K.
  • Sahraoui Fouad
  • Chapman S. C.
  , 2013, 41, pp.SH41F-0. We present the beginnings of a large and detailed observational survey of the properties of near and sub-ion scale turbulent fluctuations in the near-Earth solar wind. We use approximately 20 intervals of spacecraft data from the Cluster mission - a quarter of which are from periods when the instruments were operating in burst mode and can thus access near-electron scales. We supplement this data from Cluster by a large and extensive subset of intervals from the entire Wind mission (1994 - to date), which sample the magnetic field for frequencies below 11 Hz and thus sample around the ion spatial scales. Both these data sets were chosen with stringent conditions e.g. in solar wind, not connected to bow shock, no CMEs or holes, sufficient sample size and time duration, stationarity of plasma parameters etc.; and crucially, that they sample a large variety of plasma conditions e.g. varying ion and electron plasma beta, fast and slow wind, periods throughout solar cycle etc. We will be exclusively focusing on plasma and magnetic field measurements. Thus, this study and the variety of plasma parameters represented in the observational data it uses, aligns well with the aims of the recently proposed and community-driven 'Turbulent Dissipation Challenge'. The results of the following investigations will be presented: 1./ Plasma beta variation of the magnetic compressibility ratio scanning from the inertial range to near and sub-ion scales; this is also linked to the component (variance) anisotropy of the fluctuations. Due to its ease of calculation from an observational view, it is also a useful measure (although slightly redundant) to distinguish between different wave modes - Whistlers or kinetic Alfven waves - in theories that suggest that the turbulence is mediated by the various linear waves supported by the plasma; although a more general description of the behaviour of the magnetic compressibility can be furnished by considering the Hall physics. 2./ A thorough and exhaustive study of whether the intermittency and scaling changes seen by some of the authors in earlier papers (Kiyani et al. 2009, 2013) and also seen by other kinetic simulation and observational studies (Wu et al. 2013) when crossing the inertial range to the dissipation range are ubiquitous in all intervals studied; thereby lending support to the hypothesis that this behavior is at least robust to parameter variations − if not universal to weakly collisional plasmas in general. Speculative comments will be made to why this scaling change occurs. 3./ Other solar wind variations of the above calculated quantities e.g. in varying wind speed, change in bulk parameters etc. 4./ Evidence to support the existence, if any, of a transition range between the inertial and dissipation ranges, and its behaviour in the light of points 1 and 2 above. It is our assertion that some of the above findings (especially point 2 above) can be used as an observational benchmark - albeit phenomenological - on theories of the dissipation of turbulence in weakly collisional plasmas, as well as for the various models and theories upon which simulations are founded.
• ON THE NATURE, THE SCALING AND THE ANISOTROPY OF ELECTRON DISSIPATION RANGE IN SOLAR WIND TURBULENCE
  
  • Sahraoui Fouad
  , 2013.
• Energetic electron acceleration by unsteady magnetic reconnection (Invited)
  
  • Fu H.
  • Khotyaintsev Y. V.
  • Vaivads A.
  • Retinò Alessandro
  • Andre M.
  • Cao J.B.
  , 2013, 13, pp.SM13E-05. It is poorly understood how energetic electrons are produced during magnetic reconnection, which is a fundamental process responsible for stellar flares, substorms, and disruptions in fusion experiments. Observations in the solar chromosphere and the Earth's magnetosphere indicate significant electron acceleration during reconnection, while in the solar wind, energetic electrons are absent. Here we show that energetic electron acceleration is caused by unsteady reconnection. In the Earth's magnetosphere and the solar chromosphere, reconnection is unsteady, so that energetic electrons are produced; in the solar wind, reconnection is steady, so energetic electrons are absent. The acceleration mechanism is quasi-adiabatic: betatron and Fermi acceleration in outflow jets are two processes contributing to electron energization during unsteady reconnection. The localized betatron acceleration in the outflow is responsible for at least half of the energy gain for the peak observed fluxes.
• CLUSTER observation of polar electron precipitation above the polar caps during periods of Northward IMF
  
  • Fontaine Dominique
  • Maggiolo R.
  , 2013, 21, pp.SM21D-07. The CLUSTER spacecraft revealed the presence of successive current sheets of opposite polarity above the polar caps during periods of northward or weak IMF. We first present the general electrodynamical context. At CLUSTER altitude (5-7 RE), the upward part of this current system consists of ion beams accelerated by quasi-static electric fields, associated with precipitating electrons. They are surrounded by low energy upflowing electron beams carrying a downward current. We then focus on the precipitating electrons above the polar cap which form acceleration structures at about 100 - 300 eV. This acceleration is interpreted as the effect of an electrostatic potential along magnetic field lines located above CLUSTER altitude, i.e. typically above 5-7 RE. We present statistics on the characteristics of these precipitating electron structures and we discuss the source regions and the mechanisms possibly at their origin.
• Radiative Signatures of Z-Pinch Plasmas at UNR: from X-Pinches to Wire Arrays
  
  • Safronova Alla S.
  • Kantsyrev Viktor L.
  • Esaulov A. A.
  • Safronova U. I.
  • Shlyaptseva V. V.
  • Shrestha Ishor
  • Osborne Glenn C.
  • Weller Michael E.
  • Stafford A.
  • Keim S. F.
  • Cooper M. C.
  • Chuvatin Alexandre S.
  , 2014, 32, pp.1460316. University-scale Z-pinch generators are able to produce High Energy Density (HED) plasmas in a broad range of plasma parameters under well-controlled and monitored experimental conditions suitable for radiation studies. The implosion of X-pinch and wire array loads at a 1 MA generator yields short (1-20 nsec) x-ray bursts from one or several bright plasma spots near the wire cross point (for X-pinches) or along and near Z-pinch axis (for wire arrays). Such X- and Z-pinch HED plasma with scales from a few &#956;m to several mm in size emits radiation in a broad range of energies from 10 eV to 0.5 MeV and is subject of our studies during the last ten years. In particular, the substantial number of experiments with very different wire loads was performed on the 1 MA Zebra generator and analyzed: X-pinch, cylindrical, nested, and various types of the novel load, Planar Wire Arrays (PWA). Also, the experiments at an enhanced current of 1.5-1.7 MA on Zebra using Load Current Multiplier (LCM) were performed. This paper highlights radiative signatures of X-pinches and Single and Double PWAs which are illustrated using the new results with combined wire loads from two different materials. (10.1142/S2010194514603160)
  DOI : 10.1142/S2010194514603160
• Plasmas dans l’eau et aux interfaces
  
  • Marinov Ilya
  , 2013. L'intérêt croissant susciter par les applications biomédicales des plasmas non thermiques, inspire le développement de nouvelles sources plasmas. Les décharges à barrière diélectrique (DBD) ou les décharges couronne générées dans l'air ambiant ou dans le flux de gaz rare sont généralement utilisées. Production des plasmas directement dans un liquide a un grand potentiel pour les processus de stérilisation des substances liquides et pour le traitement extracorporel du sang. Les mécanismes physiques de formation d’une décharge électrique dans un milieu liquide ne sont toujours pas entièrement compris .La première partie de cette thèse examine le sujet de l'initiation et le développement de décharge nanoseconde dans les diélectriques liquides (eau déminéralisée, éthanol et n-pentane). La visualisation ombroscopique résolue en temps, la spectroscopie optique d'émission et les mesures électrique sont appliqués à l’étude d’une décharge électrique initiée sur une électrode à pointe positive.Nous avons montré que, selon l'amplitude de tension trois scénarios différents peuvent se produire dans des diélectriques polaires, notamment, la cavitation d'une bulle, le développement de décharge dans une cavité gazeuse (le mode ‘buisson’) et l'initiation de la décharge filamentaire (le mode ‘arborescent’) se propageant directement dans le liquide. La différence dans la formation et la propagation de deux modes de la décharge (‘buisson’ et ‘arbre’) révèle les mécanismes physiques étant très distincts.Dans la deuxième partie de ce travail, nous abordons la question d’interaction entre les plasmas froids atmosphériques avec les cellules vivantes in vitro et in vivo. L’étude porte sur le mécanisme de la mort cellulaire induite par le plasma. Cytométrie de flux avec deux marqueurs AnnexinV (AV) et de l'iodure de propidium (PI) a été appliquée pour l’analyse de la viabilité cellulaire. On montre l’induction de l' apoptose dans les cellules de T lymphocyte humain (Jurkat) et dans les cellules épithéliales (HMEC) traités par le plasma de DBD nanoseconde. Dans les souris nudes l'induction de l'apoptose et de la nécrose en fonction de la dose est observé par la microscopie électronique dans les coupes de l'épiderme. L'analyse histologique montre l’apparition des lésions importantes dans l'épiderme , derme, hypoderme et les muscles en fonction de la durée du traitement. Production de peroxyde d'hydrogène dans le milieu de culture (PBS) exposé au plasma de DBD est mesurée à l’aide d’une sonde fluorescente sélective (Amplex® Red). La viabilité des cellules de la thyroïde humaines ( HTori -3) et des cellules de mélanome (1205Lu) cellules démontre la dépendance nonmonotone de la concentration de H2O2. Le rôle majeur du peroxyde d'hydrogène produit par plasma et du champ électrique de la DBD est suggéré.
• Anisotropic Magnetoresistance Magnetometer for inertial navigation systems
  
  • Mohamadabadi Kaveh
  , 2013. This work addresses the relevant errors of the anisotropic magnetoresistance sensor for inertial navigation systems. The manuscript provides resulting guidelines and solution for using the AMR sensors in a robust and appropriate way relative to the applications. New methods also are proposed to improve the performance and, reduce the power requirements and cost design of the magnetometer. The new compensation method is proposed by developing an optimization algorithm. The necessity of the sensor calibration is shown and the source of the errors and compensating model are investigated. Two novel methods of indoor calibration are proposed and examples of operating systems are presented.