Publications

2014

Dynamique des Plasmas à Couplage Inductive dans les gaz HBr, Cl2 et O2 et mixtures: Diagnostiques Laser et Absorption Ultraviolet Large-Bande
- Booth Jean-Paul
- Foucher Mickaël
- Chabert Pascal
, 2014. Les plasmas à couplage inductive dans les mélanges de gaz HBr, Cl2 et O2 à basse pression (1-100mTorr) sont très largement utilisées dans lindustrie microélectronique pour graver le poly- silicium afin de fabriquer les portes des transistors CMOS dans les circuits intégrées. De nombreuses modèles (de type « globale », ou hybride fluide-Monte Carlo a 2 dimensions) ont été développées pour ces systèmes, néanmoins il y eu très peu de mesures expérimentales des densités absolues des espèces transitoires (électrons, ions, atomes et radicaux libres) permettant de tester rigoureusement ces modèles. Notre projet vise à combler ce déficit, en employant une panoplie de techniques de mesure à travers une grande plage de paramètres (pression, compostions du gaz et puissance RF injectée). Les désaccords ainsi constatées permettent de comprendre et remédier les lacunes dans les modèles. Parmi les techniques employées, on peut citer la sonde résonante micro-onde « hairpin » (densité électronique), la spectroscopie de fluorescence induit par laser a deux photons pour les atomes (O, Cl (deux états spin-orbite), Br) avec différents schémas détalonnage en absolue, et la spectroscopie dabsorption large bande pour les molécules. Nous avons construit un nouveau banc dabsorption, utilisant un plasma induit par laser comme source de lumière « corps noir », des optiques achromatiques et un spectromètre « Isoplan » corrigé en aberration. Ce montage permet denregistrer des spectres sur une très grande plage spectrale (250nm en mono-coup) avec un niveau de bruit exceptionnellement bas (5x10-5). Ainsi nous avons observé les spectres des états vibrationellement excités du Cl2 et de lO2, ainsi que plusieurs produits du type ClxOy. Parmi les conclusions importantes de ce travail, nous constatons que les températures translationelles, rotationnelles et vibrationnelles des molécules peuvent devenir très élevés dans ces systèmes. Ceci à un impact direct sur la densité du gaz (à pression constant) et donc la collisionalité des électrons. Il est ainsi nécessaire de bien tenir compte des processus de transfert dénergie et le bilan de chauffage du gaz dans la construction dune modèle fiable.
Electromagnetic generation of strong shocks in low pressure gas
- Singh Raj Laxmi
- Larour Jean
- Stehlé Chantal
- Ciardi Andrea
, 2014. affiche P71 atelier 12 PNPS The interstellar medium (ISM) is a wide object of research, especially for the phenomena leading to the building up of protostellar objects, like mass accretion or outflows and jets. Accretion shocks are of particular interest as their radiative signature can be related to the rate of mass accretion onto the forming star. In recent years, laboratory plasma experiments have been developed to study radiative shocks relevant to astrophysics. These scaled models of accretion shocks have been successfully generated on high power lasers by launching a fast moving piston in a stationary gaseous medium. Complementary to experiments on lasers, pulsed power generators are also able to create astrophysically relevant shocks. On these facilities, high-intensity currents can produce magnetic fields of several Tesla which act as a piston, accelerating an annular plasma sheath and driving a strong shock in a tenuous gas. The results presented will describe the pulsed power setup and a lumped-parameter model, linking the transient discharge dynamics and quantities like mass and speed of the plasma sheath. The results of this 0-D model will be compared to 3-D MHD simulations performed with the code GORGON. This work has lead to an optimization process of the setup. The diagnostics which are currently implemented will be presented to illustrate the model as well as experimental records of the plasma speed. Work supported by DIM ACAV Île-de-France region, Labex PLAS@PAR (ANR-11-IDEX-0004-02), Observatoire de Paris-Meudon and UPMC university.
Reply on the comment of the paper "New probing techniques of radiative shocks
- Stehlé Chantal
- Kozlova Michaela
- Larour Jean
- Nejdl Jaroslav
- Suzuki-Vidal Francisco
- Cohen Mathieu
- Chaulagain Uddhab P.
- Champion Norbert
- Barroso Patrice
- Acef Ouali
- Delattre Pierre-Alexandre
- Dostal Jan
- Krus Miroslav
- Chièze Jean-Pierre
- Ibgui Laurent
Optics Communications, Elsevier, 2014, 318, pp.226-230. Imaging the structure of a radiative shock is a challenging task as the high plasma densities produced need a short wavelength to penetrate the plasma, requiring highly sophisticated imaging techniques. In a recent paper (Stehlé et al., Opt. Commun. 285 (2012) 6469 [1]) the feasibility of a novel imaging technique using an X-ray laser (XRL) at 21 nm with a pulse duration 0.15 ns was proved. The recorded image was attributed to a shock propagating with a velocity of ~60 km/s. This velocity is in agreement with measurements of the plasma self-emission using time and space resolved diode diagnostics, and also in qualitative agreement with 1D numerical simulations. However, due to the inhomogeneous reflectivity of the XUV imaging mirror and to the low number of XRL photons, the quality of the recorded image was insufficient to unambiguously identify the different shock regions. Thus, arguing an ad hoc spatial resolution of ~0.5 mm and a stepwise representation of the shockpiston system, the potential of the technique to observe a radiative precursor was contested (Busquet's comment (in press) [2]). In this reply we aim at clarifying different aspects of the experimental setup, spatial resolution and other questions raised in this comment in order to back up our findings together with their respective analysis and interpretations. (10.1016/j.optcom.2013.12.006)
DOI : 10.1016/j.optcom.2013.12.006
Laboratory Modeling of Rotation in Accreting Astrophysical Objects Using Pulsed Power Plasma Accelerators.
- Chuvatin Alexandre S.
- Safronova Alla S.
- Kantsyrev Viktor L.
- Esaulov A. A.
- Shreshta I.
- Shlyaptseva V. V.
- Weller Michael E.
- Stafford A.
- Gasilov V. A.
- Boldarev A. S.
- Olkhovskaya O. G.
- Bagdasarov G. A.
- Gasilova V.
- Dorofeeva E. Y.
- Zucchini Frédéric
- Grunenwald Julien
- Maillard T.
, 2014.
Double planar Wire Arrays at enhanced Current on Zebra
- Safronova Alla S.
- Kantsyrev Viktor L.
- Shreshta I.
- Weller Michael E.
- Shlyaptseva V. V.
- Stafford A.
- Lorance M. Y.
- Esaulov V. V.
- Chuvatin Alexandre S.
- Coverdale C. A.
- Jones B.
- Ampleford D. J.
, 2014. Double Planar Wire Arrays (DPWA), which consist of two parallel rows of wires, have demonstrated high radiation efficiency (up to 30 kJ), compact size (1.5-3 mm), and pulse shaping capabilities in experiments at 1 MA Zebra. DPWAs are also very suitable for the new compact multi-source hohlraum concept. It was shown that their implosion dynamics strongly depends on the critical load parameter, the aspect ratio (width to inter-planar gap Δ). Recently, we studied larger sized DPWAs at the increased current of 1.5-1.7 MA that provided enhanced energy coupling in plasma and better diagnostic access to observable plasma regions. The new regimes of implosions with asymmetric jets, no precursor formation and very early radiation for larger sized DPWAs (Δ=9 mm) with low aspect ratio of 0.54 were demonstrated. As a development of this work, new experiments at the enhanced current with the DPWAs from Alumel (mostly Ni) with Δ=6 mm and higher aspect ratio were performed. The different implosion and radiative signatures were observed that are presented and analyzed such as formation of the precursor in the middle of the array, no foot pulse emission but a very broad XRD signal, and L-shell radiation before the XRD peak but not so early as for larger PWAs. Also, simultaneously with soft x-ray L-shell Ni radiation, hard x-ray K-shell Ni radiation was recorded in a broad range from 13 ns before up to 18 ns after the XRD peak showing the temporal evolution of characteristic cold Ni Kα emission as well as some adjacent spectral features from hotter plasmas. Non-LTE modeling of such K-shell features provided time history of ionization balance of Ni ions and is compared with results of L-shell modeling. (10.1109/PLASMA.2014.7012642)
DOI : 10.1109/PLASMA.2014.7012642
Analysis of K-shell HED Plasmas in X-Pinch and Laser Experiments at UNR
- Stafford A.
- Safronova Alla S.
- Kantsyrev Viktor L.
- Weller Michael E.
- Shlyaptseva V. V.
- Wiewior P.
- Shreshta I.
- Osborne Glenn C.
- Keim S. F.
- Chuvatin Alexandre S.
, 2014. Summary form only given. High Energy Density (HED) plasmas were produced in two sets of experiments: using a Z-pinch generator and a high power laser at the Nevada Terawatt Facility (NTF) of the University of Nevada, Reno (UNR). Each experiment has its unique characteristics and can be used to gain better understanding of HED plasmas. X-pinch experiments were performed at enhanced current on the Zebra generator using the Load Current Multiplier (LCM) and generated radiation yield up to 19 kJ/cm. These experiments used Ti alloy wires (6% Al, 4% V) for a first look at X-pinches at 1.5-1.7 MA at UNR. A full set of diagnostics was fielded including time-integrated spatially-resolved (TISR) and time-gated spatially-integrated (TGSI) x-ray spectrometers, time-integrated and time-gated pinhole x-ray cameras, and shadowgraphy. Many interesting results were found such as: i) the appearance of characteristic emission of Ti (wire material) and Fe (anode) in different orders of reflection at 30 ns prior to the first x-ray burst that was recorded for the next 15 ns, ii) prominent K-shell Al radiation despite the low percentage of Al in the alloy in both TGSI and TISR spectra, iii) K-shell Al radiation that corresponds to 400-550 eV plasmas starting near the first x-ray burst. Additionally experiments using the Leopard laser were performed on flat Al targets using a 0.8 ns pulse duration and two different target thicknesses (10 and 50 μm) that produced K-shell Al spectra of higher electron density. K-shell Al spectra of X-pinches, both TGSI and TISR, were modeled and compared with the laser-produced plasma results. The advantage of using alloyed Ti wires to study K-shell HED plasmas is highlighted. Future work is discussed. (10.1109/PLASMA.2014.7012507)
DOI : 10.1109/PLASMA.2014.7012507
Fluctuations à petites échelles en direction axiale dans les plasmas des propulseurs à effet Hall
- Honoré Cyrille
- Tsikata Sedina
- Cavalier J.
- Coulette D.
- Lemoine N.
- Héron A.
- Grésillon D.
, 2014. Dans les plasmas des propulseurs à effet Hall, les électrons montrent une mobilité anormale à travers le champ magnétique présent en sortie de canal. Des modèles linéaires et des simulations PIC ont montré que cette mobilité était liée à la présence dune fluctuation à léchelle millimétrique dans la direction azimutale du canal du propulseur. Des observations par diffusion collective ont confirmé la présence de ces instabilités. Ces mêmes observations ont montré la présence dune autre fluctuation présente aux mêmes échelles, mais principalement dans la direction axiale du propulseur. Les modèles linéaires montrent que cette fluctuation a une nature différente de celle de linstabilité azimutale.
Physique des plasmas capacitifs excités par des formes d'ondes complexes
- Chabert Pascal
, 2014.
Characteristics of Jupiter's Magnetospheric Turbulence Observed by the Galileo Spacecraft
- Tao Chihiro
- Sahraoui Fouad
- Fontaine Dominique
- de Patoul Judith
- Chust Thomas
- Retinò Alessandro
, 2014.
Inductively-coupled plasmas (ICP) of Cl2,O2 and mixtures : measurements of atoms, ClxOy and electron densities
- Foucher Mickaël
- Carbone Emile
- Booth Jean-Paul
- Chabert Pascal
, 2014.
Inductively-coupled plasmas of Cl2, O2 and mixtures : measurement of atoms, ClxOy and electron densities
- Foucher Mickaël
- Carbone Emile
- Booth Jean-Paul
- Chabert Pascal
, 2014.
Ground-state bromine atoms measurements by Two-Photon Absorption Laser-Induced Fluorescence
- Foucher Mickaël
- Carbone Emile
- Booth Jean-Paul
- Chabert Pascal
, 2014.
Radiative shocks at PALS: latest results and future prospects
- Stehlé Chantal
- Chaulagain Uddhab
- de Sà Lionel
- Ibgui Laurent
- Ciardi Andrea
- Larour Jean
- Kozlová Michaela
- Nejdl Jaroslav
- Suzuki-Vidal Francisco
- Barroso Patrice
- Velarde P.
- Rodriguez Perez R.
- Gil J. M.
- Espinosa G.
- Acef Ouali
, 2014. affiche P53 Being able to produce and diagnose radiative shocks under controlled laboratory conditions is a key aspect to understand their role in astrophysical processes such as accretion in stellar formation. The ongoing study of radiative shocks using high-power lasers has significantly advanced our understanding on the physics of these complex flows. In particular, experiments at the Prague Asterix Laser System (PALS) have demonstrated the formation of radiative shocks in Xenon with a characteristic velocity of 50-60 km/s. Latest results on the generation on radiative shocks at PALS demonstrate the feasibility of fielding novel probing techniques such as time-resolved imaging using an X-ray laser at 21.2 nm, allowing to probe simultaneously the high-density shock-front together with the lower-density radiative precursor in front of the shock. These results will be compared with 2-D radiative-hydrodynamic simulations using the code ARWEN. Future experimental campaigns will focus on spectroscopic measurements of the different shock regions together with new experimental configurations such as the interaction of counter-streaming radiative shocks. These prospects will be presented and discussed from both experimental and simulation point of view. This work is supported by french ANR STARSHOCK (grant 08-BLAN-0263-07), Programme National de Physique Stellaire" (PNPS) of CNRS/INSU, France, Observatoire de Paris and labex Plas@Par ( ANR-11-IDEX-0004-02 )
Optimization of an electromagnetic generator for strong shocks in low pressure gas
- Larour Jean
- Singh Raj Laxmi
- Stehlé Chantal
- Ciardi Andrea
- Chaulagain Uddhab
- Suzuki-Vidal Francisco
, 2014. affiche P41 Accretion and ejection processes are key elements to predict the evolution of Young Star Objects (YSOs) and their feedback to the interstellar medium. The observational signature of accretion is correlated to the presence of a strong shock which forms when the matter from a circumstellar disk hits the photosphere of the star. In this context, laboratory plasma astrophysics is a powerful tool to study the dynamics of these hypersonic processes. In parallel with experimental studies of radiative shocks in moderate pressure Xenon, driven by high-power lasers (U. Chaulagain et al., this conf.), strong shocks in low pressure rare gases can be generated using a very different technique: an electromagnetic gun. A low-inductance high-voltage generator at the kJ level drives a high current pulse, peaking at 150 kA in a 1-μs risetime. The principles of plasma sheath formation and acceleration are presented and modeled with a lumped circuit. A parametric study of the generator, coupled to the moving plasma, is presented, leading to proposed optimized geometries. A passive optical diagnostic is used to measure the shock profile and speed (typ. 20 km/s). In order to pre-process other complementary diagnostics, detailed MHD simulations, using the GORGON code, give reference information for the plasma parameters of the moving ionized sheath. Work supported by DIM ACAVÎle-de-France region, Labex PLAS@PAR (ANR-11-IDEX-0004-02), Observatoire de Paris and UPMC university.
Météorologie de l'Espace
- Amory-Mazaudier Christine
, 2014. Lecture introductive à la météorologie de l'Espace
Structure of a laser-driven radiative shock
- Chaulagain Uddhab
- Stehlé Chantal
- Larour Jean
- Kozlová Michaela
- Suzuki-Vidal Francisco
- Barroso Patrice
- Cotelo M.
- Velarde P.
- Rodriguez R.
- Gil J. M.
- Ciardi Andrea
- Acef Ouali
- Nejdl Jaroslav
- de Sà Lionel
- Singh Raj Laxmi
- Ibgui Laurent
- Champion Norbert
, 2015, 17 A, pp.106 - 113. Radiative shocks are ubiquitous in stellar environments and are characterized by high temperature plasma emitting a considerable fraction of their energy as radiation. The physical structure of these shocks is complex and experimental benchmarks are needed to provide a deeper understanding of the physics at play. In addition, experiments provide unique data for testing radiation hydrodynamics codes which, in turn, are used to model astrophysical phenomena. Radiative shocks have been studied on various high-energy laser facilities for more than a decade, highlighting the importance of radiation on the plasma dynamics. Particularly the PALS facility has focused in producing radiative shocks with typical velocities of ∼5060 km s−1 in xenon at a fraction of a bar. In addition PALS has the unique capability of producing the most powerful XUV laser available today (21.2 nm (58.4 eV), 0.15 ns), opening the door to new diagnostics of dense plasmas. Here we present results of XUV imaging of the precursor and post-shock structure of radiative shocks generated in xenon in this facility, together with time-and-space resolved measurements of the XUV self-emission using fast diode. The experimental results are interpreted with the help of 2D ARWEN radiative hydrodynamics simulations and state-of-the art monochromatic opacities.
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.
, 2014, 16, pp.12841. In spring 2013, the Cluster spacecraft 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 could 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.
Themis observations of whistler wave normal angles
- Taubenschuss U.
- Khotyaintsev Y. V.
- Vaivads A.
- Santolík O.
- Cully C. M.
- Le Contel Olivier
- Angelopoulos V.
, 2014, 16, pp.6511. Since spring 2007, the five Themis spacecraft have monitored the vicinity of Earth along orbits, which reach from the dayside solar wind until far down Earth's magnetotail. A magnetometer (SCM) and an electric field instrument (EFI) onboard Themis can be operated in a wave-burst mode which allows for sampling of magnetic and electric waveforms with a rate of up to 8192 Hz. These waveform snapshots have been subject to spectral and polarization analysis. The computed parameters fill a database which is established in the frame of the MAARBLE project ("Monitoring, Analyzing and Assessing Radiation Belt Energization and Loss"). Among those parameters is the direction of the wave-vector with respect to the ambient magnetic field. We present first results on the distribution of those wave normal angles from whistler mode emission. While propagating away from the source region, wave normal angles of whistler are believed to change from parallel to more oblique orientations. We study the wave-vectors both on the nightside, where source regions are close to the equatorial plane, and on the dayside, where sources can also be found at high latitudes.
In situ observations of suprathermal ion acceleration in the near-Earth jet braking region
- Retinò Alessandro
- Khotyaintsev Y. V.
- Vaivads A.
- Le Contel Olivier
- Fu H.S.
- Zieger B.
- Kronberg Elena
, 2014, 16, pp.14772. Plasma jet fronts and braking regions are sites of substantial particle acceleration in planetary magnetospheres and are considered to play a major role in other distant environments such as the solar corona and astrophysical jets. Jet fronts are the boundaries separating ambient from jetting plasma (e.g. due to reconnection) while jet braking regions is where jets are eventually stopped/diverted. A number of recent in situ observations in the Earth's magnetotail have allowed studying in detail electron acceleration mechanisms at jet fronts/braking region therein. Yet, observations of suprathermal ion acceleration are scarce. Here we show Cluster spacecraft observations of suprathermal ions up to ~ 1 MeV (about 10 times the thermal energy) in the near-Earth jet braking region. Observations indicate that ions are trapped between large-scale oppositely-directed jets and accelerated therein by strong electric fields.
Suprathermal electron acceleration within flux tube at magnetic flux pile-up front
- Vaivads A.
- Khotyaintsev Y. V.
- Retinò Alessandro
- Fu H.S.
- Kronberg E. A.
- Daly P.
, 2014, 16, pp.3515. The acceleration of energetic electrons inside magnetic pile-up regions of plasma jets in the Earth magnetotail is studied in details for one case observed by Cluster. The case has been selected based on high observed fluxes of electrons, Cluster being in the burst mode and Cluster separation being around 1000 km that is optimal for studies of ion scale physics. We show that during this event there are present two characteristic acceleration mechanisms. First, significant acceleration is achieved due to magnetic flux pile-up, consistent with betatron acceleration. Secondly, in this case magnetic island like 3D structures are forming in front of the pile-up region and we observe strong electron acceleration inside those. Energetic electrons inside magnetic island have more parallel anisotropy and thus can escape along the magnetic field from the acceleration place and can generate low altitude radio emissions as observed.
The Alfvén Mission: A possible ESA M4 Mission Candidate
- Fazakerley A.
- Berthomier Matthieu
- Pottelette Raymond
- Forsyth C.
, 2014, 16, pp.13153. The Alfvén mission was proposed to the ESA M3 call for missions in 2010. Its scientific objective was to study the Auroral Acceleration Region (AAR), the most accessible laboratory for investigating plasmas at an interface where ideal magneto-hydrodynamics does not apply. Alfvén was designed to teach us where and how the particles that create the aurorae are accelerated, how and why they emit auroral kilometric radiation, what creates and maintains large scale electric fields aligned with the magnetic field, and to elucidate the ion outflow processes which are slowly removing the Earth's atmosphere. The auroral regions are the interface connecting the solar wind-driven collisionless magnetosphere to the collisional ionosphere at the top of Earth's atmosphere. Solar wind energy, transmitted via the magnetosphere, is dissipated in this interface, often explosively during magnetic substorms. The plasma organizes itself on a hierarchy of spatial and temporal scales, manifesting as auroral structures ranging from huge long-lived arcs to tiny flickering filaments. The only way to make substantial further progress in auroral plasma science and to elucidate the fundamental physics of the acceleration processes at the heart of magnetosphere-ionosphere coupling is to combine the advantages of high-time resolution in situ measurements (as pioneered by the FAST mission), with the advantages of multi-point measurements (as pioneered by Cluster) in one mission. The mission concept also envisages continuous auroral imaging from the spacecraft, guaranteeing an understanding of the context (auroral morphology and motion) within which the in situ plasma measurements are made, and strong coordination with the existing dense network of ground based observatories, for more detailed ionospheric and auroral information when Alfvén overflights occur. We will review the ESA M3 Alfvén concept, consider recent scientific progress in this area, and discuss possible developments of the concept for a possible ESA M4 proposal.
Electron scale physics in magnetic reconnection
- Hesse Michael
- Aunai N.
- Kuznetsova M. M.
- Zenitani Seiji
, 2014, 16, pp.2461. Magnetic reconnection involves, for each particle species, a diffusion region, within which charged particles become unmagnetized and diffuse across the magnetic field. Naturally, electrons tend to remain magnetized even if ion species already lose their tie to individual flux tubes. It is therefore of great interest to investigate electron behavior in magnetic reconnection. This talk will focus first on the mechanism, by which electrons provide the resistive force to balance the acceleration of the reconnection electric field. We will identify the underlying mechanism by means of investigating the electron distribution function. We will then use theoretical analyses to develop a universal equation, which captures apparent electron behavior and predicts the magnitude of the reconnection electric field.
Remote sensing of a NTC radio source from a Cluster tilted spacecraft pair
- Décréau Pierrette
- Kougblénou Séna
- Lointier Guillaume
- Rauch Jean-Louis
- Trotignon Jean-Gabriel
- Vallières Xavier
- Canu Patrick
- Rochel Grimald Sandrine
- El-Lemdani Mazouz Farida
- Darrouzet Fabien
, 2014, 16, pp.2014 - 16046. The non-thermal continuum (NTC) radiation is a radio wave produced within the magnetosphere of a planet. It has been observed in space around Earth since the '70s, and within the magnetospheres of other planets since the late '80s. A new study using ESA's Cluster mission has shown improved precision in determining the source of various radio emissions produced by the Earth. The experiment involved tilting one of the four identical Cluster spacecraft to measure the electric field of this emission in three dimensions for the first time. Our analysis of a NTC case event pinpointed a small deviation from the generally assumed (circular) polarization of this emission. We show that classical triangulation, in this case using three of the spacecraft located thousands of kilometres apart, can lead to an erroneous source location. A second method, using the new 3D electric field measurements, indicated a source located along the plasmapause at medium geomagnetic latitude, far away from the source location estimated by triangulation. Cluster observations reveal that this NTC source emits from the flank of the plasmapause towards the polar cap. Understanding the source of NTC waves will help with the broader understanding of their generation, amplification, and propagation.
3D plasma camera for planetary missions
- Berthomier Matthieu
- Morel Xavier
- Techer Jean-Denis
, 2014, 16, pp.14245. A new 3D field-of-view toroidal space plasma analyzer based on an innovative optical concept allows the coverage of 4pi str solid angle with only two sensor heads. It fits the need of all-sky thermal plasma measurements on three-axis stabilized spacecraft which are the most commonly used platforms for planetary missions. The 3D plasma analyzer also takes advantage of the new possibilities offered by the development of an ultra low-power multi-channel charge sensitive amplifier used for the imaging detector of the instrument. We present the design and measured performances of a prototype model that will fly on a test rocket in 2014.
Kinetic Turbulence in the Terrestrial Magnetosheath: Cluster Observations
- Huang S. Y.
- Sahraoui Fouad
- Deng X. H.
- He Jiansen
- Yuan Z. G.
- Zhou M.
- Pang Y.
- Fu H.S.
, 2014, 16, pp.11191. We present a first statistical study of subproton and electron scales turbulence in the terrestrial magnetosheath using waveform data measured by the Cluster/STAFF Search Coil Magnetometer (SCM) in the frequency range [1, 180] Hz. It is found that clear spectral breaks exist near the electron scale, which separate two power-law like frequency bands referred to as the dispersive and the electron dissipation ranges. The frequencies of the breaks fb are shown to be well correlated with the electron gyroscale rhoe rather than with the electron inertial length de. The distribution of the slopes below fb is found to be narrow and peaks near -2.9, while that of the slopes above fb is found broader, peaks near -5.2 and has values as low as -7.5. This is the first time that such steep power-law spectra are reported in space plasma turbulence. These observations provide strong constraints on theoretical modeling of kinetic turbulence and dissipation in collisionless magnetized plasmas.

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