Publications

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Below, by year, are the publications listed in the HAL open archive.

2017

Interplay between Alfvén and magnetosonic waves in compressible magnetohydrodynamics turbulence
- Andrés Nahuel
- Leoni P. Clark Di
- Mininni P. D.
- Dmitruk P.
- Sahraoui Fouad
- Matthaeus W. H.
Physics of Plasmas, American Institute of Physics, 2017, 24, pp.102314. Using spatio-temporal spectra, we show direct evidence of excitation of magnetosonic and Alfvén waves in three-dimensional compressible magnetohydrodynamic turbulence at small Mach numbers. For the plasma pressure dominated regime, or the high beta regime (with beta the ratio between fluid and magnetic pressure), and for the magnetic pressure dominated regime, or the low beta regime, we study magnetic field fluctuations parallel and perpendicular to a guide magnetic field B0. In the low beta case, we find excitation of compressible and incompressible fluctuations, with a transfer of energy towards Alfvénic modes and to a lesser extent towards magnetosonic modes. In particular, we find signatures of the presence of fast magnetosonic waves in a scenario compatible with that of weak turbulence. In the high beta case, fast and slow magnetosonic waves are present, with no clear trace of Alfvén waves, and a significant part of the energy is carried by two-dimensional turbulent eddies. (10.1063/1.4997990)
DOI : 10.1063/1.4997990
Stable and unstable roots of ion temperature gradient driven mode using curvature modified plasma dispersion functions
- Gultekin Ozgur
- Gürcan Özgür D.
Plasma Physics and Controlled Fusion, IOP Publishing, 2017, 60 (2), pp.025021. Basic, local kinetic theory of ion temperature gradient driven (ITG) mode, with adiabatic electrons is reconsidered. Standard unstable, purely oscillating as well as damped solutions of the local dispersion relation are obtained using a bracketing technique that uses the argument principle. This method requires computing the plasma dielectric function and its derivatives, which are implemented here using modified plasma dispersion functions with curvature and their derivatives, and allows bracketing/following the zeros of the plasma dielectric function which corresponds to different roots of the ITG dispersion relation. We provide an open source implementation of the derivatives of modified plasma dispersion functions with curvature, which are used in this formulation. Studying the local ITG dispersion, we find that near the threshold of instability the unstable branch is rather asymmetric with oscillating solutions towards lower wave numbers (i.e. drift waves), and damped solutions toward higher wave numbers. This suggests a process akin to inverse cascade by coupling to the oscillating branch towards lower wave numbers may play a role in the nonlinear evolution of the ITG, near the instability threshold. Also, using the algorithm, the linear wave diffusion is estimated for the marginally stable ITG mode. (10.1088/1361-6587/aa9e27)
DOI : 10.1088/1361-6587/aa9e27
QDB: a new database of plasma chemistries and reactions
- Tennyson Jonathan
- Rahimi Sara
- Hill Christian
- Tse Lisa
- Vibhakar Anuradha
- Akello-Egwel Dolica
- Brown Daniel B
- Dzarasova Anna
- Hamilton James R
- Jaksch Dagmar
- Mohr Sebastian
- Wren-Little Keir
- Bruckmeier Johannes
- Agarwal Ankur
- Bartschat Klaus
- Annemie Bogaerts Annemie
- Booth Jean-Paul
- Goeckner Matthew J
- Hassouni Khaled
- Itikawa Yukikazu
- Braams Bastiaan J
- Krishnakumar E.
- Laricchiuta Annarita
- Mason Nigel J
- Pandey Sumeet
- Petrovic Zoran Lj
- Pu Yi-Kang
- Ranjan Alok
- Rauf S.
- Schulze J.
- Turner M.M.
- Ventzek Peter
- Whitehead J.C.
- Yoon Jung-Sik
Plasma Sources Science and Technology, IOP Publishing, 2017, 26 (5), pp.055014. One of the most challenging and recurring problems when modeling plasmas is the lack of data on the key atomic and molecular reactions that drive plasma processes. Even when there are data for some reactions, complete and validated datasets of chemistries are rarely available. This hinders research on plasma processes and curbs development of industrial applications. The QDB project aims to address this problem by providing a platform for provision, exchange, and validation of chemistry datasets. A new data model developed for QDB is presented. QDB collates published data on both electron scattering and heavy-particle reactions. These data are formed into reaction sets, which are then validated against experimental data where possible. This process produces both complete chemistry sets and identifies key reactions that are currently unreported in the literature. Gaps in the datasets can be filled using established theoretical methods. Initial validated chemistry sets for SF 6 /CF 4 /O 2 and SF 6 /CF 4 /N 2 /H 2 are presented as examples. (10.1088/1361-6595/aa6669)
DOI : 10.1088/1361-6595/aa6669
Promoting lentil germination and stem growth by plasma activated tap water, demineralized water and liquid fertilizer
- Zhang Shiqiang
- Rousseau Antoine
- Dufour Thierry
RSC Advances, Royal Society of Chemistry, 2017, 7 (50), pp.31244–31251. Tap water, demineralized water and liquid fertilizer have been activated using an atmospheric pressure plasma jet (APPJ) to investigate their benefits for the germination rate and stem elongation rate of lentils from Puy-en-Velay (France). By plasma-activating tap water, we have obtained germination rates as high as 80% (instead of 30% with tap water). Also, higher stem elongation rates and final stem lengths were obtained using activated tap water compared with commercial fertilizer. We show that these rates of germination and stem growth strongly depend on the combination of two radicals generated in the liquids by the plasma: hydrogen peroxide and nitrate. This synergy appears to be a condition for releasing seed dormancy through the endogenous production of NO radicals. (10.1039/C7RA04663D)
DOI : 10.1039/C7RA04663D
Intrinsic non-inductive current driven by ETG turbulence in tokamaks
- Kaw P. K.
- Singh R.
- Gürcan Özgür D.
Physics of Plasmas, American Institute of Physics, 2017, 24, pp.102303. Motivated by observations and physics understanding of the phenomenon of intrinsic rotation, it is suggested that similar considerations for electron dynamics may result in intrinsic current in tokamaks. We have investigated the possibility of intrinsic non-inductive current in the turbulent plasma of tokamaks. Ohm's law is generalized to include the effect of turbulent fluctuations in the mean field approach. This clearly leads to the identification of sources and the mechanisms of non-inductive current drive by electron temperature gradient turbulence. It is found that a mean parallel electro-motive force and hence a mean parallel current can be generated by (1) the divergence of residual current flux density and (2) a non-flux like turbulent source from the density and parallel electric field correlations. Both residual flux and the non-flux source require parallel wave-number k∥ symmetry breaking for their survival which can be supplied by various means like mean E × B shear, turbulence intensity gradient, etc. Estimates of turbulence driven current are compared with the background bootstrap current in the pedestal region. It is found that turbulence driven current is nearly 10% of the bootstrap current and hence can have a significant influence on the equilibrium current density profiles and current shear driven modes. (10.1063/1.4990746)
DOI : 10.1063/1.4990746
Absolute ozone densities in a radio-frequency driven atmospheric pressure plasma using two-beam UV-LED absorption spectroscopy and numerical simulations
- Wijaikhum A.
- Schröder D.
- Schröter S.
- Gibson A. R.
- Niemi K.
- Friderich J.
- Greb A.
- Schulz-von der Gathen V.
- O'Connell D.
- Gans T.
Plasma Sources Science and Technology, IOP Publishing, 2017, 26. The efficient generation of reactive oxygen species (ROS) in cold atmospheric pressure plasma jets (APPJs) is an increasingly important topic, e.g. for the treatment of temperature sensitive biological samples in the field of plasma medicine. A 13.56 MHz radio-frequency (rf) driven APPJ device operated with helium feed gas and small admixtures of oxygen (up to 1%), generating a homogeneous glow-mode plasma at low gas temperatures, was investigated. Absolute densities of ozone, one of the most prominent ROS, were measured across the 11 mm wide discharge channel by means of broadband absorption spectroscopy using the Hartley band centred at lambda = 255 nm. A two-beam setup with a reference beam in Mach--Zehnder configuration is employed for improved signal-to-noise ratio allowing high-sensitivity measurements in the investigated single-pass weak-absorbance regime. The results are correlated to gas temperature measurements, deduced from the rotational temperature of the N2 (C 3 {{{\Pi }}}u \to B 3 {{{\Pi }}}g , upsilo = 0 \to 2) optical emission from introduced air impurities. The observed opposing trends of both quantities as a function of rf power input and oxygen admixture are analysed and explained in terms of a zero-dimensional plasma-chemical kinetics simulation. It is found that the gas temperature as well as the densities of O and O2(b{}1{{{Sigma }}}g ) influence the absolute O3 densities when the rf power is varied. (10.1088/1361-6595/aa8ebb)
DOI : 10.1088/1361-6595/aa8ebb
Space Weather, from the Sun to the Earth, the key role of GNSS. Part II: Training on daily Global Positioning System (GPS) data
- Amory-Mazaudier Christine
- Fleury Rolland
- Gadimova Sharafat
- Touzani Abderrahmane
Coordinates, 2017, 13 (3), pp.31-36. The goal of this paper is to give a clear view of the Sun Earth relationships that are complex. The phenomena acting at large scales and essentially related to dynamic and electromagnetic physical processes have been addressed. Besides physics, the work done to develop the training in Space Weather by focusing on Global Navigation Satellite Systems has also been presented. Readers may recall that we published the first part of this article which focused on physics of the relationships Sun, Earth and Meteorology of Space. In this issue, aspects of GNSS training and capacity building are discussed.
Experimental study of the interaction of two laser-driven radiative shocks at the PALS laser
- Singh R. L.
- Stehlé C.
- Suzuki-Vidal F.
- Kozlova M.
- Larour Jean
- Chaulagain U.
- Clayson T.
- Rodriguez R.
- Gil M.
- Nejdl J.
- Krus M.
- Dostal J.
- Dudzak R.
- Barroso P.
- Acef O.
- Cotelo M.
- Velarde P.
High Energy Density Physics, Elsevier, 2017, 23, pp.20 - 30. Radiative shocks (RS) are complex phenomena which are ubiquitous in astrophysical environments. The study of such hypersonic shocks in the laboratory, under controlled conditions, is of primary interest to understand the physics at play and also to check the ability of numerical simulations to reproduce the experimental results. In this context, we conducted, at the Prague Asterix Laser System facility (PALS), the first experiments dedicated to the study of two counter-propagating radiative shocks propagating at non-equal speeds up to 25–50 km/s in noble gases at pressures ranging between 0.1 and 0.6 bar. These experiments highlighted the interaction between the two radiative precursors. This interaction is qualitatively but not quantitatively described by 1D simulations. Preliminary results obtained with XUV spectroscopy leading to the estimation of shock temperature and ion charge of the plasma are also presented. (10.1016/j.hedp.2017.03.001)
DOI : 10.1016/j.hedp.2017.03.001
Influence of neutral pressure on instability enhanced friction and ion velocities at the sheath edge of two-ion-species plasmas
- Adrian P. J.
- Baalrud S. D.
- Lafleur T.
Physics of Plasmas, American Institute of Physics, 2017, 24. The Instability Enhanced Friction theory [Baalrud et al., Phys. Rev. Lett. 103, 205002 (2009)] is extended to account for the influence of neutral pressure in predicting the flow speed of each ion species at the sheath edge of plasmas containing two ion species. Particle-in-cell simulations show that the theory accurately predicts both the neutral pressure cutoff of ion-ion two-stream instabilities and the ion flow speeds at the sheath edge as pressure is varied over several orders of magnitude. The simulations are used to directly calculate the instability-enhanced ion-ion friction force. At sufficiently high neutral pressure, the simulations also provide evidence for collisional modifications to the Bohm criterion. (10.1063/1.4986239)
DOI : 10.1063/1.4986239
Enhanced control of the ionization rate in radio-frequency plasmas with structured electrodes via tailored voltage waveforms
- Doyle Scott J.
- Lafleur Trevor
- Gibson Andrew R.
- Tian Peng
- Kushner Mark J.
- Dedrick James
Plasma Sources Science and Technology, IOP Publishing, 2017, 26. Radio-frequency capacitively coupled plasmas that incorporate structured electrodes enable increases in the electron density within spatially localized regions through the hollow cathode effect (HCE). This enables enhanced control over the spatial profile of the plasma density, which is useful for several applications including materials processing, lighting and spacecraft propulsion. However, asymmetries in the powered and grounded electrode areas inherent to the hollow cathode geometry lead to the formation of a time averaged dc self-bias voltage at the powered electrode. This bias alters the energy and flux of secondary electrons leaving the surface of the cathode and consequentially can moderate the increased localized ionization afforded by the hollow cathode discharge. In this work, two-dimensional fluid-kinetic simulations are used to demonstrate control of the dc self-bias voltage in a dual-frequency driven (13.56, 27.12 MHz), hollow cathode enhanced, capacitively coupled argon plasma over the 66.6--200 Pa (0.5--1.5 Torr) pressure range. By varying the phase offset of the 27.12 MHz voltage waveform, the dc self-bias voltage varies by 10%--15% over an applied peak-to-peak voltage range of 600--1000 V, with lower voltages showing higher modulation. Resulting ionization rates due to secondary electrons within the hollow cathode cavity vary by a factor of 3 at constant voltage amplitude, demonstrating the ability to control plasma properties relevant for maintaining and enhancing the HCE. (10.1088/1361-6595/aa96e5)
DOI : 10.1088/1361-6595/aa96e5
Controlling plasma properties under differing degrees of electronegativity using odd harmonic dual frequency excitation
- Gibson Andrew R.
- Gans Timo
Plasma Sources Science and Technology, IOP Publishing, 2017, 26. The charged particle dynamics in low-pressure oxygen plasmas excited by odd harmonic dual frequency waveforms (low frequency of 13.56 MHz and high frequency of 40.68 MHz) are investigated using a one-dimensional numerical simulation in regimes of both low and high electronegativity. In the low electronegativity regime, the time and space averaged electron and negative ion densities are approximately equal and plasma sustainment is dominated by ionisation at the sheath expansion for all combinations of low and high frequency and the phase shift between them. In the high electronegativity regime, the negative ion density is a factor of 15--20 greater than the low electronegativity cases. In these cases, plasma sustainment is dominated by ionisation inside the bulk plasma and at the collapsing sheath edge when the contribution of the high frequency to the overall voltage waveform is low. As the high frequency component contribution to the waveform increases, sheath expansion ionisation begins to dominate. It is found that the control of the average voltage drop across the plasma sheath and the average ion flux to the powered electrode are similar in both regimes of electronegativity, despite the differing electron dynamics using the considered dual frequency approach. This offers potential for similar control of ion dynamics under a range of process conditions, independent of the electronegativity. This is in contrast to ion control offered by electrically asymmetric waveforms where the relationship between the ion flux and ion bombardment energy is dependent upon the electronegativity. (10.1088/1361-6595/aa8dcd)
DOI : 10.1088/1361-6595/aa8dcd
Counterpropagating radiative shock experiments on the Orion laser
- Suzuki-Vidal Francisco
- Clayson Thomas
- Stehlé Chantal
- Swadling G. F.
- Foster J.
- Skidmore J.
- Graham P.
- Burdiak G.
- Lebedev S. V.
- Chaulagain Uddhab
- Singh Raj Laxmi
- Gumbrell E.
- Patankar S.
- Spindloe C.
- Larour Jean
- Kozlová Michaela
- Rodriguez Perez R.
- Gil J. M.
- Espinosa G.
- Velarde P.
- Danson C.
Physical Review Letters, American Physical Society, 2017, 119 (05), pp.055001. We present new experiments to study the formation of radiative shocks and the interaction between two counterpropagating radiative shocks. The experiments are performed at the Orion laser facility, which is used to drive shocks in xenon inside large aspect ratio gas cells. The collision between the two shocks and their respective radiative precursors, combined with the formation of inherently three-dimensional shocks, provides a novel platform particularly suited for the benchmarking of numerical codes. The dynamics of the shocks before and after the collision are investigated using point-projection x-ray backlighting while, simultaneously, the electron density in the radiative precursor was measured via optical laser interferometry. Modeling of the experiments using the 2D radiation hydrodynamic codes NYM and PETRA shows very good agreement with the experimental results. (10.1103/PhysRevLett.119.055001)
DOI : 10.1103/PhysRevLett.119.055001
Long-lived laser-induced arc discharges for energy channeling applications
- Point Guillaume
- Arantchouk Léonid
- Thouin Emmanuelle
- Carbonnel Jérôme
- Mysyrowicz André
- Houard Aurélien
Scientific Reports, Nature Publishing Group, 2017, 7 (1), pp.13801. Laser filamentation offers a promising way for the remote handling of large electrical power in the form of guided arc discharges. We here report that it is possible to increase by several orders of magnitude the lifetime of straight plasma channels from filamentation-guided sparks in atmospheric air. A 30 ms lifetime can be reached using a low-intensity, 100 mA current pulse. Stability of the plasma shape is maintained over such a timescale through a continuous Joule heating from the current. This paves the way for applications based on the generation of straight, long duration plasma channels, like virtual plasma antennas or contactless transfer of electric energy. (10.1038/s41598-017-14054-z)
DOI : 10.1038/s41598-017-14054-z
Erratum: "On the Existence of the Kolmogorov Inertial Range in the Terrestrial Magnetosheath Turbulence" (2017, ApJL, 836, L10)
- Huang S. Y.
- Hadid Lina
- Sahraoui Fouad
- Yuan Z. G.
- Deng X. H.
The Astrophysical Journal Letters, Bristol : IOP Publishing, 2017, 837 (2), pp.L31. Not Available (10.3847/2041-8213/aa633c)
DOI : 10.3847/2041-8213/aa633c
Differential kinetic physics of solar-wind minor ions
- Perrone Denise
- Valentini F.
- Servidio S.
- Stabile S.
- Pezzi O.
- Sorriso-Valvo L.
- de Marco R.
- Marcucci M. F.
- Brienza D.
- Bruno Roberto
- Lavraud Benoit
- Retinò Alessandro
- Vaivads A.
- Consolini G.
- de Keyser J.
- Salatti M.
- Veltri P.
, 2017, 19, pp.13382. The solar wind, although predominantly constituted of protons, is also made up of a finite amount of alpha particles, together with a few percent of heavier ions. The kinetic properties of heavy ions in the solar wind are known to behave in a well organized way under most solar-wind flow conditions: their speeds are faster than that of hydrogen by about the local Alfvén speed, and their kinetic temperatures are more than proportional to their mass. Preferential heating and acceleration of heavy ions in the solar wind and corona represent a long-standing theoretical problem in space physics, and are distinct experimental signatures of kinetic processes occurring in collisionless plasmas. However, due to very scarce measurements of heavy ions at time resolutions comparable with their kinetic scales, energy partition between species in turbulent plasma dissipation is basically unexplored. For the moment, most of the information comes from numerical simulations and a crucial support is given by self-consistent, fully nonlinear Vlasov models. Here, hybrid Vlasov-Maxwell simulations are used to investigate the role of kinetic effects in a two-dimensional turbulent multi-ion plasma, composed of kinetic protons and alpha particles, and fluid electrons. The response of different ion species to the fluctuating electromagnetic fields appears to be different. In particular, a significant differential heating of alpha particles with respect to protons is observed, localized nearby the peaks of ion vorticity and where strong deviations from thermodynamic equilibrium are recovered. Then, the understanding of the complex process of particle heating results strongly related to the study of the non-Maxwellian features on the three-dimensional ion velocity distributions. These numerical results highlight the importance for the future space missions to provide detailed ion measurements to make a significant step forward in the problem of heating in turbulent space plasmas.
MMS observations of whistler waves in electron diffusion region
- Cao D.
- Fu H.S.
- Cao J.B.
- Wang T. Y.
- Graham D. B.
- Chen Z. Z.
- Peng F. Z.
- Huang S. Y.
- Khotyaintsev Y. V.
- André M.
- Russell C. T.
- Giles B. L.
- Lindqvist P.-A.
- Torbert R. B.
- Ergun R. E.
- Le Contel Olivier
- Burch J. L.
Geophysical Research Letters, American Geophysical Union, 2017, 44 (9), pp.3954-3962. Whistler waves that can produce anomalous resistivity by affecting electrons' motion have been suggested as one of the mechanisms responsible for magnetic reconnection in the electron diffusion region (EDR). Such type of waves, however, has rarely been observed inside the EDR so far. In this study, we report such an observation by Magnetospheric Multiscale (MMS) mission. We find large-amplitude whistler waves propagating away from the X line with a very small wave-normal angle. These waves are probably generated by the perpendicular temperature anisotropy of the 300 eV electrons inside the EDR, according to our analysis of dispersion relation and cyclotron resonance condition; they significantly affect the electron-scale dynamics of magnetic reconnection and thus support previous simulations. (10.1002/2017GL072703)
DOI : 10.1002/2017GL072703
Evidence and relevance of spatially chaotic magnetic field lines in MCF devices
- Firpo Marie-Christine
- Lifschitz Agustin
- Ettoumi Wahb
- Farengo Ricardo
- Ferrari Hugo
- Garcia-Martinez Pablo Luis
Plasma Physics and Controlled Fusion, IOP Publishing, 2017, 59 (3). Numerical evidence for the existence of spatially chaotic magnetic field lines about the collapse phase of tokamak sawteeth with incomplete reconnection is presented. This uses the results of extensive test particle simulations in different sets of electromagnetic perturbations tested against experimental JET measurements. In tokamak sawteeth, that form a laboratory prototype of magnetic reconnection, the relative magnetic perturbation δB/B may reach a few percents. This does not apply to tokamak operating regimes dominated by turbulence where δB/B is usually not larger than 10 −4. However, this small magnetic perturbation being sustained by a large spectrum of modes is shown to be sufficient to ensure the existence of stochastic magnetic field lines. This has important consequences for magnetic confinement fusion (MCF) where electrons are dominantly governed by the magnetic force. Indeed some overlap between magnetic resonances can locally induce chaotic magnetic field lines enabling the spatial redistribution of the electron population and of its thermal content. As they are the swiftest plasma particles, electrons feed back the most rapid perturbations of the magnetic field (10.1088/1361-6587/aa570d)
DOI : 10.1088/1361-6587/aa570d
Optical emission spectrum of filamentary nanosecond surface dielectric barrier discharge
- Shcherbanev S.A.
- Khomenko A.Yu.
- Stepanyan S.A.
- Popov N.A.
- Starikovskaia Svetlana
Plasma Sources Science and Technology, IOP Publishing, 2017, 26 (2), pp.02LT01 (7pp). Streamer-to-filament transition is a general feature of high pressure high voltage (HV) nanosecond surface dielectric barrier discharges. The transition was studied experimentally using time- and space-resolved optical emission in UV and visible parts of spectra. The discharge was initiated by HV pulses 20 ns in duration and 2 ns rise time, positive or negative polarity, 2060 kV in amplitude on the HV electrode. The experiments were carried out in a single-shot regime at initial pressures P > 3 bar and ambient initial temperature in air, N2, H2:N2 and O2:Ar mixtures. It was shown that the transition to filamentary mode is accompanied by the appearance of intense continuous radiation and broad atomic lines. Electron density calculated from line broadening is characterized by high absolute values and long decay in the afterglow. The possible reasons for the continuous spectra were analyzed. (10.1088/1361-6595/26/2/02LT01)
DOI : 10.1088/1361-6595/26/2/02LT01
The role of thermal energy accommodation and atomic recombination probabilities in low pressure oxygen plasmas
- Gibson Andrew
- Foucher Mickaël
- Marinov Daniil
- Chabert Pascal
- Gans T.
- Kushner M.J.
- Booth Jean-Paul
Plasma Physics and Controlled Fusion, IOP Publishing, 2017, 59 (2), pp.024004. Surface interaction probabilities are critical parameters that determine the behaviour of low pressure plasmas and so are crucial input parameters for plasma simulations that play a key role in determining their accuracy. However, these parameters are difficult to estimate without in situ measurements. In this work, the role of two prominent surface interaction probabilities, the atomic oxygen recombination coefficient ? O and the thermal energy accommodation coefficient ? E in determining the plasma properties of low pressure inductively coupled oxygen plasmas are investigated using two-dimensional fluid-kinetic simulations. These plasmas are the type used for semiconductor processing. It was found that ? E plays a crucial role in determining the neutral gas temperature and neutral gas density. Through this dependency, the value of ? E also determines a range of other plasma properties such as the atomic oxygen density, the plasma potential, the electron temperature, and ion bombardment energy and neutral-to-ion flux ratio at the wafer holder. The main role of ? O is in determining the atomic oxygen density and flux to the wafer holder along with the neutral-to-ion flux ratio. It was found that the plasma properties are most sensitive to each coefficient when the value of the coefficient is small causing the losses of atomic oxygen and thermal energy to be surface interaction limited rather than transport limited. (10.1088/1361-6587/59/2/024004)
DOI : 10.1088/1361-6587/59/2/024004
Localized reversal of the perpendicular velocity in Tore Supra ohmic, L-mode, limited plasmas
- Trier Elisée
- Hennequin Pascale
- Gürcan Özgür D.
- Sabot R.
- Bucalossi J.
- Guimarães-Filho Z.O.
- Bourdelle C.
- Clairet F.
- Falchetto G.
- Fenzi C.
- Garbet X.
- Maget P.
- Vermare Laure
- The Tore Supra Team
Nuclear Fusion, IOP Publishing, 2017, 57 (4), pp.046021. In Tore Supra plasmas, the perpendicular velocity measured by Doppler reflectometry was observed to reverse in a localized zone close to a normalized radius???0.5?0.6, changing from a negative value (corresponding to a negative radial electric field E r ) to a positive value ( ##IMG## [http://ej.iop.org/images/0029-5515/57/4/046021/nfaa59bbieqn001.gif] E_\textr>0 ). This occurs in L-mode, ohmic plasmas with a negligible external momentum input, a non-circular limited cross-section, and an edge safety factor close to 3. This reversal is favoured by a decrease in the magnetic field, or an increase in density. It is accompanied by a characteristic behaviour of the MHD activity signal, whose amplitude decrease during a ramp-down of the edge safety factor as it approaches ##IMG## [http://ej.iop.org/images/0029-5515/57/4/046021/nfaa59bbieqn002.gif] q_a∼ 3.1 ?3.2. A m / n ??=??2/1 mode is involved in the mechanism causing these observations. (10.1088/1741-4326/aa59bb)
DOI : 10.1088/1741-4326/aa59bb
Advanced Ion Mass Spectrometer for Giant Planet Ionosphere, Magnetospheres and Moons
- Sittler E.C.
- Cooper J.F.
- Paschalidis N.
- Jones S.
- Brinkerhoff William
- Paterson W. R.
- Ali Ashraf
- Coplan M.A.
- Chornay D.
- Sturners S.J.
- Benna Mehdi
- Bateman F.B.
- Fontaine Dominique
- Verdeil Christophe
- Andre N.
- Blanc Michel
- Wurz Peter
, 2017, pp.T1.023. We present our Advanced Ion Mass Spectrometer (AIMS) for outer planet missions which has been under development from various NASA sources (NASA Living with a Star Instrument Development (LWSID), NASA Astrobiology Instrument Development (ASTID), NASA Goddard Internal Research and Development (IRAD)s) to measure elemental, isotopic, and simple molecular composition abundances of 1 V to 25 kV hot ions with wide field-of-view (FOV) in the 1 - 60 amu mass range at mass resolution M/ DeltaM <= 60 over a wide dynamic range of particle intensities and penetrating radiation background from the inner magnetospheres of Jupiter and Saturn to the outer magnetospheric boundary regions and the upstream solar wind. This instrument will work for both spinning spacecraft and 3-axis stabilized spacecraft. AIMS will measure the ion velocity distribution functions (VDF) for the individual ion species from which velocity moments will give their ion density, flow velocity and temperature.
On the historical origins of the CEJ, DP2 and Ddyn current systems and their roles in the predictions of ionospheric responses to geomagnetic storms at equatorial latitudes
- Amory-Mazaudier Christine
- Bolaji O. S.
- Doumbia V.
Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2017. In this short letter, we recall the differences between the Counter electrojet (CEJ), which is a phenomenon observed on the magnetically quiet days and the disturbance dynamo (Ddyn), which can be observed during and after a geomagnetic storm. The CEJ is well-known to occur near the geomagnetic dip equator. It can be identified by a reversal in the horizontal component (H) of the geomagnetic field daily regular variations. In contrasts to equatorial electrojet (EEJ) that flows eastward in the daytime the CEJ in considered to flow westward. The magnetic signatures of the reversed solar quiet (Sq) current at the low latitude during magnetic storms are due to the Ddyn. This disturbance (Ddyn) is produced by current systems that are driven by thermospheric storm winds originating from the Joule heating of enhanced high latitude currents. The DP2 is the magnetic effect of current systems at high latitudes. These currents are associated with the coupling of magnetosphere and ionosphere through geomagnetic field lines. They are associated to the magnetospheric convection. During intense magnetic storms these high latitude currents are enhanced and their magnetic effects can extend toward the low latitudes This work shows that the study of magnetic perturbations makes it possible to understand the disturbances of the ionospheric electric currents. The use of an efficient treatment of the magnetic signals makes it possible to separate the magnetic effects of the different perturbations PPEF and DDEF. This was performed in the paper Nava et al. (2016). (10.1002/2017JA024132)
DOI : 10.1002/2017JA024132
Transfer of microwave energy along a filament plasma column in air
- Prade Bernard
- Houard Aurélien
- Larour Jean
- Pellet Michel
- Mysyrowicz André
Applied Physics B - Laser and Optics, Springer Verlag, 2017, 123, pp.40. We demonstrate the coupling of microwave radiation into a plasma channel formed by laser filamentation in air, leading to the amplification by two orders of magnitude of longitudinal oscillations of the plasma. Transfer of this longitudinal excitation towards unexcited region of the plasma column occurs over more than 10 cm, in good agreement with a theoretical model describing the propagation of a TM wave guided along the surface between air and plasma. We foresee that high power low frequency electromagnetic waves injected into a multi-filament plasma could initiate and sustain a long-lived plasma over several meters distance. (10.1007/s00340-016-6616-4)
DOI : 10.1007/s00340-016-6616-4
Acceleration of energetic electrons by waves in inhomogeneous solar wind plasmas
- Krafft C.
- Volokitin A.
Journal of Plasma Physics, Cambridge University Press (CUP), 2017, 83 (2), pp.705830201. The paper studies the influence of the background plasma density fluctuations on the dynamics of the Langmuir turbulence generated by electron beams, for parameters typical for solar type III beams and plasmas near 1 AU. A self-consistent Hamiltonian model based on the Zakharov and the Newton equations is used, which presents several advantages compared to the Vlasov approach. Beams generating Langmuir turbulence can be accelerated as a result of wave transformation effects or/and decay cascade processes; in both cases, the beam-driven Langmuir waves transfer part of their energy to waves of smaller wavenumbers, which can be reabsorbed later on by beam particles of higher velocities. As a consequence, beams can conserve a large part of their initial kinetic energy while propagating and radiating wave turbulence over long distances in inhomogeneous plasmas. Beam particles can also be accelerated in quasi-homogeneous plasmas due to the second cascade of wave decay, the wave transformation processes being very weak in this case. The net gains and losses of energy of a beam and the wave turbulence it radiates are calculated as a function of the average level of plasma density fluctuations and the beam parameters. The results obtained provide relevant information on the mechanism of energy reabsorption by beams radiating Langmuir turbulence in solar wind plasmas. (10.1017/S0022377817000174)
DOI : 10.1017/S0022377817000174
The nonlinear behavior of whistler waves at the reconnecting dayside magnetopause as observed by the Magnetospheric Multiscale mission: A case study
- Wilder F. D.
- Ergun R. E.
- Newman D. L.
- Goodrich K. A.
- Trattner K. J.
- Goldman M. V.
- Eriksson S.
- Jaynes A. N.
- Leonard T.
- Malaspina D. M.
- Ahmadi N.
- Schwartz S. J.
- Burch J. L.
- Torbert R. B.
- Argall M. R.
- Giles B. L.
- Phan T. D.
- Le Contel Olivier
- Graham D. B.
- Khotyaintsev Yu V.
- Strangeway R. J.
- Russell C. T.
- Magnes W.
- Plaschke F.
- Lindqvist P.-A.
Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2017, 122 (5), pp.5487-5501. We show observations of whistler mode waves in both the low-latitude boundary layer (LLBL) and on closed magnetospheric field lines during a crossing of the dayside reconnecting magnetopause by the Magnetospheric Multiscale (MMS) mission on 11 October 2015. The whistlers in the LLBL were on the electron edge of the magnetospheric separatrix and exhibited high propagation angles with respect to the background field, approaching 40°, with bursty and nonlinear parallel electric field signatures. The whistlers in the closed magnetosphere had Poynting flux that was more field aligned. Comparing the reduced electron distributions for each event, the magnetospheric whistlers appear to be consistent with anisotropy-driven waves, while the distribution in the LLBL case includes anisotropic backward resonant electrons and a forward resonant beam at near half the electron-Alfvén speed. Results are compared with the previously published observations by MMS on 19 September 2015 of LLBL whistler waves. The observations suggest that whistlers in the LLBL can be both beam and anisotropy driven, and the relative contribution of each might depend on the distance from the X line. (10.1002/2017JA024062)
DOI : 10.1002/2017JA024062

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