Publications

2014

• Electric field in nanosecond surface dielectric barrier discharge at different polarities of the high voltage pulse: spectroscopy measurements and numerical modeling.
  
  • Stepanyan S.A.
  • Victor Soloviev
  • Starikovskaia Svetlana
  Journal of Physics D: Applied Physics, IOP Publishing, 2014. Has been just accepted
• Pure airplasma bullets propagating inside microcapillaries and in ambient air
  
  • Lacoste D.A.
  • Bourdon Anne
  • Kuribara Koichi
  • Urabe Keiichiro
  • Stauss Sven
  • Terashima Kazuo
  Plasma Sources Science and Technology, IOP Publishing, 2014, 23, pp.062006. This paper reports on the characterization of airplasma bullets in microcapillary tubes and in ambient air, obtained without the use of inert or noble gases. The bullets were produced by nanosecond repetitively pulsed discharges, applied in a dielectric barrier discharge configuration. The anode was a tungsten wire with a diameter of 50μm, centered in the microcapillary, while the cathode was a silver ring, fixed on the outer surface of the fused silica tube. The effects of the applied voltage and the inner diameter of the microcapillary tube on the plasma behavior were investigated. Inside the tubes, while the topology of the bullets seems to be strongly dependent on the diameter, their velocity is only a function of the amplitude of the applied voltage. In ambient air, the propagation of air bullets with a velocity of about 1.25 × 105 ms−1 is observed. (10.1088/0963-0252/23/6/062006)
  DOI : 10.1088/0963-0252/23/6/062006
• An electric field in nanosecond surface dielectric barrier discharge at different polarities of the high voltage pulse: spectroscopy measurements and numerical modeling
  
  • Stepanyan S.A.
  • Soloviev Victor
  • Starikovskaia Svetlana
  Journal of Physics D: Applied Physics, IOP Publishing, 2014, 47, pp.485201. The ratio of emission intensities of the second positive N2(C3Πu, v' = 0) → N2(B3Πg, v = 0), 337.1 nm and first negative, 391.4 nm systems of nitrogen have been measured in a nanosecond surface dielectric barrier discharge (SDBD). The measurements were carried out in synthetic air for a pressure range 13 bar for different polarities of the high-voltage (HV) pulse. For all the investigated conditions, the ratio of emission intensities at the wavelengthes 391.4 and 337.1 nm, measured experimentally, is systematically higher for the positive polarity of HV electrodes. To analyze the spatial distribution of N2(C3Πu) and emissions, comprehensive two-dimensional numerical modeling for P = 1 bar has been performed. The details of the formation of a narrow gap between the dielectric surface and the streamer channel in the case of positive polarity of HV electrodes are discussed. The ratio of integrated over space calculated emission intensities, , has been analyzed and compared with obtained experimental data. A good agreement was obtained for a negative polarity SDBD. For a positive polarity discharge, for all the considered conditions. Explanation for the observed effect is suggested. (10.1088/0022-3727/47/48/485201)
  DOI : 10.1088/0022-3727/47/48/485201
• Investigation of capillary nanosecond discharges in air at moderate pressure: comparison of experiments and 2D numerical modeling
  
  • Klochko A.V.
  • Starikovskaia Svetlana
  • Xiong Z.
  • Kushner M.J.
  Journal of Physics D: Applied Physics, IOP Publishing, 2014, 47, pp.365202. Nanosecond electrical discharges in the form of ionization waves are of interest for rapidly ionizing and exciting complex gas mixtures to initiate chemical reactions. Operating with a small discharge tube diameter can significantly increase the specific energy deposition and so enable optimization of the initiation process. Analysis of the uniformity of energy release in small diameter capillary tubes will aid in this optimization. In this paper, results for the experimentally derived characteristics of nanosecond capillary discharges in air at moderate pressure are presented and compared with results from a two-dimensional model. The quartz capillary tube, having inner and outer diameters of 1.5 and 3.4 mm, is about 80 mm long and filled with synthetic dry air at 27 mbar. The capillary tube with two electrodes at the ends is inserted into a break of the central wire of a long coaxial cable. A metal screen around the tube is connected to the cable ground shield. The discharge is driven by a 19 kV 35 ns voltage pulse applied to the powered electrode. The experimental measurements are conducted primarily by using a calibrated capacitive probe and back current shunts. The numerical modelling focuses on the fast ionization wave (FIW) and the plasma properties in the immediate afterglow after the conductive plasma channel has been established between the two electrodes. The FIW produces a highly focused region of electric field on the tube axis that sustains the ionization wave that eventually bridges the electrode gap. Results from the model predict FIW propagation speed and current rise time that agree with the experiment. (10.1088/0022-3727/47/36/365202)
  DOI : 10.1088/0022-3727/47/36/365202
• Regeneration of isopropyl alcohol saturated Mn<SUB>X</SUB>O<SUB>Y</SUB> surface: Comparison of thermal, ozonolysis and non-thermal plasma treatments
  
  • Sivachandiran Loganathan
  • Thévenet Frédéric
  • Rousseau Antoine
  Chemical Engineering Journal, Elsevier, 2014, 246, pp.184-195. IPA saturated MnXOY surface regeneration has been investigated under dry air. MnXOY coated glass beads packed-bed reactor has been designed and used for IPA storage under gas-flowing condition at 296 K. The coated MnXOY material is characterized by BrunauerEmmettTeller (BET), non destructive Optical Pro- filometer and X-ray diffraction (XRD) techniques. Atmospheric pressure gas phase Fourier Transform Infrared Spectroscopy (FTIR) and online Thermal Desorption coupled with Gas Phase Chromatography and Mass Spectrometry (TDGCMS) have been respectively used to quantify and to identify the gas phase species produced during the regeneration processes. This study mainly aims at investigating three different methods to regenerate the IPA saturated MnXOY surface. In this framework, methods have been investigated for IPA saturated MnXOY surface regeneration namely (i) direct thermal treatment (DTT), (ii) ozonolysis and (iii) In-Situ Non Thermal Plasma Treatment (NTP). Among the employed methods, In-Situ NTP treatment has shown better regeneration efficiency, and twice more CO2 selectivity. Notably, dry air In-Situ NTP treatment prior to thermal treatment has significantly improved the mineralization. The order of mineralization efficiency and/or COx selectivity can be written as follows: In-Situ NTP > dry air ozonolysis > dry air DTT. (10.1016/j.cej.2014.02.058)
  DOI : 10.1016/j.cej.2014.02.058
• Experimental validation of the dual positive and negative ion beam acceleration in the plasma propulsion with electronegative gases thruster
  
  • Rafalskyi D.V.
  • Popelier Lara
  • Aanesland Ane
  Journal of Applied Physics, American Institute of Physics, 2014, 115 (5), pp.053301. The PEGASES (Plasma Propulsion with Electronegative Gases) thruster is a gridded ion thruster, where both positive and negative ions are accelerated to generate thrust. In this way, additional downstream neutralization by electrons is redundant. To achieve this, the thruster accelerates alternately positive and negative ions from an ion-ion plasma where the electron density is three orders of magnitude lower than the ion densities. This paper presents a first experimental study of the alternate acceleration in PEGASES, where SF6 is used as the working gas. Various electrostatic probes are used to investigate the source plasma potential and the energy, composition, and current of the extracted beams. We show here that the plasma potential control in such system is key parameter defining success of ion extraction and is sensitive to both parasitic electron current paths in the source region and deposition of sulphur containing dielectric films on the grids. In addition, large oscillations in the ion-ion plasma potential are found in the negative ion extraction phase. The oscillation occurs when the primary plasma approaches the grounded parts of the main core via sub-millimetres technological inputs. By controlling and suppressing the various undesired effects, we achieve perfect ion-ion plasma potential control with stable oscillation-free operation in the range of the available acceleration voltages (±350&#8201;V). The measured positive and negative ion currents in the beam are about 10&#8201;mA for each component at RF power of 100&#8201;W and non-optimized extraction system. Two different energy analyzers with and without magnetic electron suppression system are used to measure and compare the negative and positive ion and electron fluxes formed by the thruster. It is found that at alternate ion-ion extraction the positive and negative ion energy peaks are similar in areas and symmetrical in position with /&#8722; ion energy corresponding to the amplitude of the applied acceleration voltage. (10.1063/1.4863876)
  DOI : 10.1063/1.4863876
• Electron energy distributions in a magnetized inductively coupled plasma
  
  • Song Sang-Heon
  • Yang Yang
  • Chabert Pascal
  • Kushner M.J.
  Physics of Plasmas, American Institute of Physics, 2014, 21 (9), pp.093512. Optimizing and controlling electron energy distributions (EEDs) is a continuing goal in plasma materials processing as EEDs determine the rate coefficients for electron impact processes. There are many strategies to customize EEDs in low pressure inductively coupled plasmas (ICPs), for example, pulsing and choice of frequency, to produce the desired plasma properties. Recent experiments have shown that EEDs in low pressure ICPs can be manipulated through the use of static magnetic fields of sufficient magnitudes to magnetize the electrons and confine them to the electromagnetic skin depth. The EED is then a function of the local magnetic field as opposed to having non-local properties in the absence of the magnetic field. In this paper, EEDs in a magnetized inductively coupled plasma (mICP) sustained in Ar are discussed with results from a two-dimensional plasma hydrodynamics model. Results are compared with experimental measurements. We found that the character of the EED transitions from non-local to local with application of the static magnetic field. The reduction in cross-field mobility increases local electron heating in the skin depth and decreases the transport of these hot electrons to larger radii. The tail of the EED is therefore enhanced in the skin depth and depressed at large radii. Plasmas densities are non-monotonic with increasing pressure with the external magnetic field due to transitions between local and non-local kinetics. (10.1063/1.4896711)
  DOI : 10.1063/1.4896711
• Les débris spatiaux : le revers de l'ère spatiale
  
  • Aanesland Ane
  • Grondein Pascaline
  Flash X - La revue scientifique de l'Ecole polytechnique, Ecole polytechnique, 2014 (16), pp.12.
• E x B shear pattern formation by radial propagation of heat flux waves
  
  • Kosuga Y.
  • Diamond P.H.
  • Dif-Pradalier Guilhem
  • Gürcan Özgür D.
  Physics of Plasmas, American Institute of Physics, 2014, 21 (5). A novel theory to describe the formation of E x B flow patterns by radially propagating heat flux waves is presented. A model for heat avalanche dynamics is extended to include a finite delay time between the instantaneous heat flux and the mean flux, based on an analogy between heat avalanche dynamics and traffic flow dynamics. The response time introduced here is an analogue of the drivers' response time in traffic dynamics. The microscopic foundation for the time delay is the time for mixing of the phase space density. The inclusion of the finite response time changes the model equation for avalanche dynamics from Burgers equation to a nonlinear telegraph equation. Based on the telegraph equation, the formation of heat flux jams is predicted. The growth rate and typical interval of jams are calculated. The connection of the jam interval to the typical step size of the E x B staircase is discussed. (C) 2014 AIP Publishing LLC. (10.1063/1.4872018)
  DOI : 10.1063/1.4872018
• Quantified energy dissipation rates in the terrestrial bow shock: 1. Analysis techniques and methodology
  
  • Wilson Iii L. B.
  • Sibeck David G.
  • Breneman A. W.
  • Le Contel Olivier
  • Cully C. M.
  • Turner D. L.
  • Angelopoulos V.
  • Malaspina D. M.
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2014, 119 (8), pp.6455-6474. We present a detailed outline and discussion of the analysis techniques used to compare the relevance of different energy dissipation mechanisms at collisionless shock waves. We show that the low-frequency, quasi-static fields contribute less to ohmic energy dissipation, (-j·E), than their high-frequency counterparts. In fact, we found that high-frequency, large-amplitude (>100 mV/m and/or >1 nT) waves are ubiquitous in the transition region of collisionless shocks. We quantitatively show that their fields, through wave-particle interactions, cause enough energy dissipation to regulate the global structure of collisionless shocks. The purpose of this paper, part one of two, is to outline and describe in detail the background, analysis techniques, and theoretical motivation for our new results presented in the companion paper. The companion paper presents the results of our quantitative energy dissipation rate estimates and discusses the implications. Together, the two manuscripts present the first study quantifying the contribution that high-frequency waves provide, through wave-particle interactions, to the total energy dissipation budget of collisionless shock waves. (10.1002/2014JA019929)
  DOI : 10.1002/2014JA019929
• Observational evidence of electron pitch angle scattering driven by ECH waves
  
  • Kurita S.
  • Miyoshi Y.
  • Cully C. M.
  • Angelopoulos V.
  • Le Contel Olivier
  • Hikishima M.
  • Misawa H.
  Geophysical Research Letters, American Geophysical Union, 2014. Using the plasma wave and electron data obtained from Time History of Events and Macroscale Interactions during Substorms, we show a signature of electron pitch angle scattering driven by Electrostatic Cyclotron Harmonic (ECH) waves in the velocity distribution function (VDF). The diffusion curve of whistler mode waves is used as a proxy to identify changes in VDFs due to wave-particle interactions. We confirm that the shape of the VDF well agrees with the diffusion curve of whistler mode waves when whistler mode chorus alone is active. On the other hand, we find that the shape of the VDF deviates from the diffusion curves at low pitch angles when ECH waves are active following the inactivation of chorus waves. The result is observational support for electron pitch angle scattering caused by ECH waves and suggests that ECH waves can contribute to generation of diffuse auroras. (10.1002/2014GL061927)
  DOI : 10.1002/2014GL061927
• Theory and Modeling for the Magnetospheric Multiscale Mission
  
  • Hesse Michael
  • Aunai Nicolas
  • Birn Joachim
  • Cassak P.
  • Denton R.~e.
  • Drake J. F.
  • Gombosi Tamas I.
  • Hoshino M.
  • Matthaeus W.
  • Sibeck David G.
  • Zenitani Seiji
  Space Science Reviews, Springer Verlag, 2014. The Magnetospheric Multiscale (MMS) mission will provide measurement capabilities, which will exceed those of earlier and even contemporary missions by orders of magnitude. MMS will, for the first time, be able to measure directly and with sufficient resolution key features of the magnetic reconnection process, down to the critical electron scales, which need to be resolved to understand how reconnection works. Owing to the complexity and extremely high spatial resolution required, no prior measurements exist, which could be employed to guide the definition of measurement requirements, and consequently set essential parameters for mission planning and execution. Insight into expected details of the reconnection process could hence only been obtained from theory and modern kinetic modeling. This situation was recognized early on by MMS leadership, which supported the formation of a fully integrated Theory and Modeling Team (TMT). The TMT participated in all aspects of mission planning, from the proposal stage to individual aspects of instrument performance characteristics. It provided and continues to provide to the mission the latest insights regarding the kinetic physics of magnetic reconnection, as well as associated particle acceleration and turbulence, assuring that, to the best of modern knowledge, the mission is prepared to resolve the inner workings of the magnetic reconnection process. The present paper provides a summary of key recent results or reconnection research by TMT members. (10.1007/s11214-014-0078-y)
  DOI : 10.1007/s11214-014-0078-y
• Comment on "Micronewton electromagnetic thruster
  
  • Lafleur Trevor
  Applied Physics Letters, American Institute of Physics, 2014, 105, pp.146101. ... (10.1063/1.4897967)
  DOI : 10.1063/1.4897967
• Numerical simulations used for a validity check on the laser induced photo-detachment diagnostic method in electronegative plasmas
  
  • Oudini N.
  • Taccogna F.
  • Bendib A.
  • Aanesland Ane
  Physics of Plasmas, American Institute of Physics, 2014, 21 (6), pp.063515. Laser photo-detachment is used as a method to measure or determine the negative ion density and temperature in electronegative plasmas. In essence, the method consists of producing an electropositive channel (negative ion free region) via pulsed laser photo-detachment within an electronegative plasma bulk. Electrostatic probes placed in this channel measure the change in the electron density. A second pulse might be used to track the negative ion recovery. From this, the negative ion density and temperature can be determined. We study the formation and relaxation of the electropositive channel via a two-dimensional Particle-In-Cell/Mote Carlo collision model. The simulation is mainly carried out in a Hydrogen plasma with an electronegativity of &#945;&#8201;=&#8201;1, with a parametric study for &#945; up to 20. The temporal and spatial evolution of the plasma potential and the electron densities shows the formation of a double layer (DL) confining the photo-detached electrons within the electropositive channel. This DL evolves into two fronts that move in the opposite directions inside and outside of the laser spot region. As a consequence, within the laser spot region, the background and photo-detached electron energy distribution function relaxes/thermalizes via collisionless effects such as Fermi acceleration and Landau damping. Moreover, the simulations show that collisional effects and the DL electric field strength might play a non-negligible role in the negative ion recovery within the laser spot region, leading to a two-temperature negative ion distribution. The latter result might have important effects in the determination of the negative ion density and temperature from laser photo detachment diagnostic. (10.1063/1.4886144)
  DOI : 10.1063/1.4886144
• Radiation from mixed multi-planar wire arrays
  
  • Safronova Alla S.
  • Kantsyrev Viktor L.
  • Esaulov A. A.
  • Chuvatin Alexandre S.
  • Weller Michael E.
  • Shlyaptseva V. V.
  • Shrestha Ishor
  • Keim S. F.
  • Stafford A.
  • Coverdale C. A.
  • Apruzese J. P.
  • Ouart N. D.
  • Giuliani J. L.
  Physics of Plasmas, American Institute of Physics, 2014, 21 (03), pp.031205. The study of radiation from different wire materials in wire array Z-pinch plasma is a very challenging topic because it is almost impossible to separate different plasmas at the stagnation. A new approach is suggested based on planar wire array (PWA) loads to assess this problem. Multi-planar wire arrays are implemented that consist of few planes, each with the same number of wires and masses but from different wire materials, arranged in parallel rows. In particular, the experimental results obtained with triple PWAs (TPWAs) on the UNR Zebra generator are analyzed with Wire Ablation Dynamics Model, non-local thermodynamic equilibrium kinetic model, and 2D radiation magneto-hydrodynamic to illustrate this new approach. In TPWAs, two wire planes were from mid-atomic-number wire material and another plane was from alloyed Al, placed either in the middle or at the edge of the TPWA. Spatial and temporal properties of K-shell Al and L-shell Cu radiations were analyzed and compared from these two configurations of TPWAs. Advantages of the new approach are demonstrated and future work is discussed. (10.1063/1.4864335)
  DOI : 10.1063/1.4864335
• CLUSTER-STAFF search coil magnetometer calibration - comparisons with FGM
  
  • Robert Patrick
  • Cornilleau-Wehrlin Nicole
  • Piberne Rodrigue
  • de Conchy Y.
  • Lacombe C.
  • Bouzid V.
  • Grison B.
  • Alison Dominique
  • Canu Patrick
  Geoscientific Instrumentation, Methods and Data Systems, European Geosciences Union, 2014, 3, pp.153-177. The main part of the Cluster Spatio-Temporal Analysis of Field Fluctuations (STAFF) experiment consists of triaxial search coils allowing the measurements of the three magnetic components of the waves from 0.1 Hz up to 4 kHz. Two sets of data are produced, one by a module to filter and transmit the corresponding waveform up to either 10 or 180 Hz (STAFF-SC), and the second by the onboard Spectrum Analyser (STAFF-SA) to compute the elements of the spectral matrix for five components of the waves, 3 × B and 2 × E (from the EFW experiment), in the frequency range 8 Hz to 4 kHz. In order to understand the way the output signals of the search coils are calibrated, the transfer functions of the different parts of the instrument are described as well as the way to transform telemetry data into physical units across various coordinate systems from the spinning sensors to a fixed and known frame. The instrument sensitivity is discussed. Cross-calibration inside STAFF (SC and SA) is presented. Results of cross-calibration between the STAFF search coils and the Cluster Fluxgate Magnetometer (FGM) data are discussed. It is shown that these cross-calibrations lead to an agreement between both data sets at low frequency within a 2% error. By means of statistics done over 10 yr, it is shown that the functionalities and characteristics of both instruments have not changed during this period. (10.5194/gi-3-153-2014)
  DOI : 10.5194/gi-3-153-2014
• Theory for helical turbulence under fast rotation
  
  • Galtier Sébastien
  Physical Review E, American Physical Society (APS), 2014, 89, pp.41001. Recent numerical simulations have shown the strong impact of helicity on homogeneous rotating hydrodynamic turbulence. The main effect can be summarized through the law n ñ=-4, where n and ñ are the power law indices of the one-dimensional energy and helicity spectra, respectively. We investigate this rotating turbulence problem in the small Rossby number limit by using the asymptotic weak turbulence theory derived previously. We show that the empirical law is an exact solution of the helicity equation where the power law indices correspond to perpendicular (to the rotation axis) wave number spectra. It is proposed that when the cascade towards small scales tends to be dominated by the helicity flux the solution tends to ñ=-2, whereas it is ñ=-3/2 when the energy flux dominates. The latter is compatible with the solution previously observed numerically and derived theoretically in the weak turbulence regime when only the energy equation is used, whereas the former solution is constrained by a locality condition. (10.1103/PhysRevE.89.041001)
  DOI : 10.1103/PhysRevE.89.041001
• Investigation of Switch Designs for the Dynamic Load Current Multiplier Scheme on the SPHYNX Microsecond Linear Transformer Driver
  
  • Maysonnave Thomas
  • Bayol Frédéric
  • Demol Gauthier
  • d'Almeida Thierry
  • Lassalle Francis
  • Morell Alain
  • Grunenwald Julien
  • Chuvatin Alexandre S.
  • Pecastaing Laurent
  • de Ferron Antoine Silvestre
  IEEE Transactions on Plasma Science, Institute of Electrical and Electronics Engineers, 2014, 42 (10), pp.2974-2980. SPHINX is a microsecond linear transformer driver LTD, used essentially for implosion of Z-pinch loads in direct drive mode. It can deliver a 6-MA current pulse within 800 ns into a Z-pinch load. The dynamic load current multiplier concept enables the current pulse to be modified by increasing its amplitude while reducing its rise time before being delivered to the load. This compact system is made up of concentric electrodes (autotransformer), a dynamic flux extruder (cylindrical wire array), a vacuum convolute (eight postholes), and a vacuum closing switch, which is the key component of the system. Several different schemes are investigated for designing a vacuum switch suitable for operating the dynamic load current multiplier on the SPHINX generator for various applications, including isentropic compression experiments and Z-pinch radiation effects studies. In particular, the design of a compact vacuum surface switch and a multichannel vacuum switch, located upstream of the load are studied. Electrostatic simulations supporting the switch designs are presented along with test bed experiments. Initial results from shots on the SPHINX driver are also presented. (10.1109/TPS.2014.2313372)
  DOI : 10.1109/TPS.2014.2313372
• Quantified energy dissipation rates in the terrestrial bow shock: 2. Waves and dissipation
  
  • Wilson Iii L. B.
  • Sibeck David G.
  • Breneman A. W.
  • Le Contel Olivier
  • Cully C. M.
  • Turner D. L.
  • Angelopoulos V.
  • Malaspina D. M.
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2014, 119 (8), pp.6475-6495. We present the first quantified measure of the energy dissipation rates, due to wave-particle interactions, in the transition region of the Earth's collisionless bow shock using data from the Time History of Events and Macroscale Interactions during Substorms spacecraft. Our results show that wave-particle interactions can regulate the global structure and dominate the energy dissipation of collisionless shocks. In every bow shock crossing examined, we observed both low-frequency (<10 Hz) and high-frequency (&#8819;10 Hz) electromagnetic waves throughout the entire transition region and into the magnetosheath. The low-frequency waves were consistent with magnetosonic-whistler waves. The high-frequency waves were combinations of ion-acoustic waves, electron cyclotron drift instability driven waves, electrostatic solitary waves, and whistler mode waves. The high-frequency waves had the following: (1) peak amplitudes exceeding deltaB 10 nT and deltaE 300 mV/m, though more typical values were deltaB 0.1-1.0 nT and deltaE 10-50 mV/m; (2) Poynting fluxes in excess of 2000 muW m<SUP>-2</SUP> (typical values were 1-10 muW m<SUP>-2</SUP>); (3) resistivities > 9000 Omega m; and (4) associated energy dissipation rates >10 muW m<SUP>-3</SUP>. The dissipation rates due to wave-particle interactions exceeded rates necessary to explain the increase in entropy across the shock ramps for 90% of the wave burst durations. For 22% of these times, the wave-particle interactions needed to only be <= 0.1% efficient to balance the nonlinear wave steepening that produced the shock waves. These results show that wave-particle interactions have the capacity to regulate the global structure and dominate the energy dissipation of collisionless shocks. (10.1002/2014JA019930)
  DOI : 10.1002/2014JA019930
• Finite ballooning angle effects on ion temperature gradient driven mode in gyrokinetic flux tube simulations
  
  • Singh Rameswar
  • Brunner Stephan
  • Ganesh R.
  • Jenko F.
  Physics of Plasmas, American Institute of Physics, 2014, 21 (3), pp.032115. This paper presents effects of finite ballooning angles on linear ion temperature gradient (ITG) driven mode and associated heat and momentum flux in Gyrokinetic flux tube simulation GENE. It is found that zero ballooning angle is not always the one at which the linear growth rate is maximum. The ITG mode acquires a short wavelength (SW) branch (k&#8869;&#961;i&#8201;>&#8201;1) when growth rates maximized over all ballooning angles are considered. However, the SW branch disappears on reducing temperature gradient showing characteristics of zero ballooning angle SWITG in case of extremely high temperature gradient. Associated heat flux is even with respect to ballooning angle and maximizes at nonzero ballooning angle while the parallel momentum flux is odd with respect to the ballooning angle. (10.1063/1.4868425)
  DOI : 10.1063/1.4868425
• Momentum transport in the vicinity of q<SUB>min</SUB> in reverse shear tokamaks due to ion temperature gradient turbulence
  
  • Singh Rameswar
  • Singh R.
  • Jhang Hogun
  • Diamond P.H.
  Physics of Plasmas, American Institute of Physics, 2014, 21 (1), pp.012302. This paper presents effects of finite ballooning angles on linear ion temperature gradient (ITG) driven mode and associated heat and momentum flux in Gyrokinetic flux tube simulation GENE. It is found that zero ballooning angle is not always the one at which the linear growth rate is maximum. The ITG mode acquires a short wavelength (SW) branch (k&#8869;&#961;i&#8201;>&#8201;1) when growth rates maximized over all ballooning angles are considered. However, the SW branch disappears on reducing temperature gradient showing characteristics of zero ballooning angle SWITG in case of extremely high temperature gradient. Associated heat flux is even with respect to ballooning angle and maximizes at nonzero ballooning angle while the parallel momentum flux is odd with respect to the ballooning angle. (10.1063/1.4861625)
  DOI : 10.1063/1.4861625
• Numerical computation of the modified plasma dispersion function with curvature
  
  • Gürcan Özgür D.
  Journal of Computational Physics, Elsevier, 2014, 269, pp.156-167. A particular generalization of the plasma dispersion function, which is linked to the regular plasma dispersion function via recurrence relations is discussed. The generalization allows a fast numerical implementation of a certain two-dimensional integral that appears in the description of the plasma dispersion in curved geometry, by reducing it to a single integral over a function involving the generalized plasma dispersion function. The local dielectric function of the toroidal ion temperature gradient driven mode can be written in terms of these integral functions. A matrix method is proposed to combine the consecutive integrals as a single 1D integral over a single integrand. The method allows two orders of magnitude speed up over the 2D integral implementation. Using various optimizations and an efficient implementation of the regular plasma dispersion function, further speed up is obtained. (C) 2014 Elsevier Inc. All rights reserved. (10.1016/j.jcp.2014.03.017)
  DOI : 10.1016/j.jcp.2014.03.017
• Experimental characterization of plasma formation and shockwave propagation induced by high power pulsed underwater electrical discharge
  
  • Claverie Alain
  • Deroy Julien
  • Boustié Michel
  • Avrillaud Gilles
  • Chuvatin Alexandre S.
  • Mazanchenko Ekaterina
  • Demol G.
  • Dramane B.
  Review of Scientific Instruments, American Institute of Physics, 2014, 85 (06), pp.063701. High power pulsed electrical discharges into liquids are investigated for new industrial applications based on the efficiency of controlled shock waves. We present here new experimental data obtained by combination of detailed high speed imaging equipments. It allows the visualization of the very first instants of plasma discharge formation, and then the pulsations of the gaseous bubble with an accurate timing of events. The time history of the expansion/compression of this bubble leads to an estimation of the energy effectively transferred to water during the discharge. Finally, the consecutive shock generation driven by this pulsating bubble is optically monitored by shadowgraphs and schlieren setup. These data provide essential information about the geometrical pattern and chronometry associated with the shock wave generation and propagation. (10.1063/1.4879715)
  DOI : 10.1063/1.4879715
• Propagation of lower-band whistler-mode waves in the outer Van Allen belt: Systematic analysis of 11 years of multi-component data from the Cluster spacecraft
  
  • Santolík O.
  • Macusova E.
  • Kolmasova Ivana
  • Cornilleau-Wehrlin Nicole
  • Conchy Y.
  Geophysical Research Letters, American Geophysical Union, 2014, 41, pp.2729-2737. Lower-band whistler-mode emissions can influence the dynamics of the outer Van Allen radiation belts. We use 11&#8201;years of measurements of the STAFF-SA instruments onboard the four Cluster spacecraft to systematically build maps of wave propagation parameters as a function of position. We determine probability distributions of wave vector angle weighted by the wave intensity. The results show that wave vector directions of intense waves are close to a Gaussian-shaped peak centered on the local magnetic field line. The width of this peak is between 10 and 20 degrees. The cumulative percentage of oblique waves is below 1015%. This result is especially significant for an important class of whistler-mode emissions of lower-band chorus at higher latitudes, well outside their source region, where a simple ray tracing model fails and another mechanism is necessary to keep the wave vectors close to the field-aligned direction. (10.1002/2014GL059815)
  DOI : 10.1002/2014GL059815
• Ionospheric disturbance dynamo associated to a coronal hole: Case study of 5-10 April 2010
  
  • Fathy Ibrahim
  • Amory-Mazaudier Christine
  • Fathy A.
  • Mahrous A. M.
  • Yumoto K.
  • Ghamry E.
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2014, 119 (5), pp.4120–4133. In this paper we study the planetary magnetic disturbance during the magnetic storm occurring on 5 April 2010 associated with high-speed solar wind stream due to a coronal hole following a coronal mass ejection. We separate the magnetic disturbance associated to the ionospheric disturbance dynamo (Ddyn) from the magnetic disturbance associated to the prompt penetration of magnetospheric electric field (DP2). This event exhibits different responses of ionospheric disturbance dynamo in the different longitude sectors (European-African, Asian, and American). The strongest effect is observed in the European-African sector. The Ddyn disturbance reduces the amplitude of the daytime H component at low latitudes during four consecutive days in agreement with the Blanc and Richmond's model of ionospheric disturbance dynamo. The amplitude of Ddyn decreased with time during the 4 days. We discuss its diverse worldwide effects. The observed signature of magnetic disturbance process in specific longitude sector is strongly dependent on which Earth's side faces the magnetic storms (i.e., there is a different response depending on which longitude sector is at noon when the SSC hits). Finally, we determined an average period of 22 h for Ddyn using wavelet analysis. (10.1002/2013JA019510)
  DOI : 10.1002/2013JA019510