Publications

2016

• Planetary Magnetosheaths: Role of Compressibility on the Scaling Properties of Turbulence
  
  • Hadid Lina
  • Sahraoui Fouad
  • Huang S. Y.
  • Galtier Sébastien
  • Banerjee Supratik
  , 2016, 48, pp.402.06. Compressible turbulence has been a subject of active research within the space physics community for the last three decades especially that it is believed to be essential for understanding the physics of the solar wind (for instance the heating of the fast wind), of the interstellar medium (in cold molecular clouds) and of other astrophysical and space phenomena.The role of the compressible fluctuations in the energy cascade in the planetary magnetosheaths is investigated with a comparison of a nearly incompressible medium, the solar wind. A focus is put on comparing the energy cascade rates estimated using the exact laws derived for incompressible MHD turbulence [Politano and Pouquet, 1998] (PP98) and for compressible isothermal turbulence recently derived by Banerjee and Galtier, 2013 (BG13).New features are evidenced using the BG13 model in comparison with the PP98 model. More interestingly, a term-by-term analysis of the compressible model emphasized the relative importance of the new compressible flux terms in the BG13 model w.r.t. to the incompressible (Yaglom) term, and provided new insight into the role played by the compressible fluctuations in the solar wind and the more compressible medium, the planetary magnetosheaths. This observational study can help improving current models of astrophysical turbulence by addressing the role of compressibility behind astrophysical shocks, in the interstellar medium or in supernova remanents.
• Entropy-complexity analysis in some globally-coupled systems
  
  • Chrisment Antoine M.
  • Firpo Marie-Christine
  Physica A: Statistical Mechanics and its Applications, Elsevier, 2016. Globally-coupled N-body systems are well-known to possess an intricate dynamics. When N is large, collective effects may drastically lower the effective dimension of the dynamics breaking the conditions on ergodicity necessary for the applicability of statistical mechanics. These problems are here illustrated and discussed through an entropy-complexity analysis of the repulsive Hamiltonian mean-field model. Using a Poincaré section of the mean-field time series provides a natural sampling time in the entropy-complexity treatment. This approach is shown to single-out the out-of-equilibrium dynamical features and to uncover a transition of the system dynamics from low-energy non-Boltzmann quasi-stationary states to high-energy stochastic-like behavior. (10.1016/j.physa.2016.05.009)
  DOI : 10.1016/j.physa.2016.05.009
• 2D Particle-In-Cell simulations of the electron-cyclotron instability and associated anomalous transport in Hall-Effect Thrusters.
  
  • Croes Vivien
  • Lafleur Trevor
  • Bonaventura Z.
  • Pechereau François
  • Bourdon Anne
  • Chabert Pascal
  , 2016. This work studies the electron-cyclotron instability in Hall-Effect Thrusters (HETs) using a 2D Particle-In-Cell (PIC) simulation. The simulation is configured with a Cartesian coordinate system where a magnetic field, B0, is aligned along the X-axis (radial direction, including absorbing walls), a constant electric field, E0, along the Z-axis (axial direction, perpendicular to simulation plane), and the E0xB0 direction along the Y-axis (O direction, with periodic boundaries). Although for low plasma densities classical electron-neutral collisions theory describes well electron transport, at sufficiently high densities (as measured in HETs) a strong instability can be observed that enhances the electron mobility, even in the absence of collisions. The instability generates high frequency (~ MHz) and short wavelength (~ mm) fluctuations in both the electric field and charged particle densities. We investigate the correlation between these fluctuations and their role with anomalous electron transport; complementing previous 1D simulations. Plasma is self-consistently heated by the instability, but since the latter does not reach saturation in an infinitely long 2D system, saturation is achieved through implementation of a finite axial length that models convection in E0 direction.
• Plasma catalyst coupling for indoor air depollution ::technological and more fundamental aspects
  
  • Rousseau Antoine
  , 2016.
• Vibrational excitation in O<SUB>2</SUB> and Cl<SUB>2</SUB> inductively-coupled plasmas and DC discharges
  
  • Guerra V.
  • Booth Jean-Paul
  • Marinov Daniil
  • Foucher Mickaël
  • Annusova Adriana
  , 2016. Low-energy electrons can interact with molecules via resonances to cause vibrational excitation with large cross-sections. Such processes can absorb significant energy from the plasma electrons, affecting the electron energy distribution and potentially (via vibration-translation (VT) energy transfer) causing substantial gas heating. The presence of vibrationally excited molecules may significant increase the rates of collisional processes, including electron dissociative attachment and electron impact dissociation into neutral atoms. However, the cross-sections of these processes are often poorly known since they are extremely difficult to measure directly, and reliable theoretical calculations are only now appearing for simple diatomic molecules. We have measured the vibrational distributions in discharges in pure O2 and pure Cl2, using high-sensitivity ultra-broadband ultraviolet absorption spectroscopy. In O2 plasmas significant vibrational excitation is observed, up to v''=18, with a tail temperature of around 8000K. In Cl2 excitation is only observed up to v''=3, and the distribution appears to be in local equilibrium with the gas translational temperature (up to 1500K). We are developing a detailed self-consistent 0D global model of these systems including vibrational excitation.
• Numerical and experimental study on the dynamics of a µs helium plasma gun with various amounts of O$_2$ admixture
  
  • Viegas Pedro
  • Damany Xavier
  • Iséni Sylvain
  • Pouvesle Jean-Michel
  • Robert Eric
  • Bourdon Anne
  , 2016. The use of admixtures (mostly O2 and N2) to a helium bu_er has been studied recently to tailor the generation of reactive species in plasma jets for biomedical applications. So far, most experiments have been dedicated to the study of the plasma plume. For endoscopic treatments, it is also important to better understand and optimize the propagation of discharges in long dielectric tubes as catheters. In this work, we present an experimental and numerical study on the dynamics of a microsecond helium plasma discharge with O2 admixture in a long dielectric tube. In simulations, a 2D fluid model is used. For comparison purposes, the geometries of the set-ups used for simulations and experiments are as close as possible. We compare experiments and simulations for di_erent amounts of O2 admixture added to the buffer gas and present results on the velocity of the discharge front for the various amounts of O2 and different applied voltages. In order to study the inuence of di_erent amounts of O2 admixture on the helium discharge dynamics, detailed kinetic schemes have been used. The influence of Penning and charge exchange reactions on the discharge structure and dynamics are studied, as well as the role of negative ions. P.V. is supported by an EDOM fellowship, and X.D. by an INEL/Region Centre-Val de Loire fellowship.
• Numerical investigation of propagation and decay of a fast ionization wave generated by nanosecond pulsed discharge
  
  • Zhu Yifei
  • Starikovskaia Svetlana
  • Babaeva N Yu
  • Kushner M.J.
  , 2016.
• What could be the role of numerical simulations in our field?
  
  • Chabert Pascal
  , 2016.
• Frequency dependence of the Electrical Asymmetry Effect in electronegative capacitive RF discharges driven by Tailored Voltage Waveforms
  
  • Schulze J.
  • Schuengel E.
  • Bruneau Bastien
  • Johnson E.V.
  • Booth Jean-Paul
  • Derzsi A.
  • Donko Z.
  • O'Connell D.
  • Gas T.
  , 2016. Capacitively coupled RF plasmas operated in CF4 at 80 Pa and driven by voltage waveforms composed of four consecutive harmonics are investigated for different fundamental driving frequencies (2.86 - 13.56 MHz) using PIC/MCC simulations and an analytical model. In contrast to previous findings in electropositive discharges the absolute value of the DC self-bias generated via the Electrical Asymmetry Effect for peak waveforms is found to increase as the fundamental frequency is reduced, providing an increased range over which it can be tuned by phase control. The analytical model reveals that this increased DC self-bias is caused by changes in the spatial profile and the mean value of the net charge density in the grounded electrode sheath induced by varying the fundamental driving frequency for peak waveforms. The spatio-temporally resolved simulation data show that as the frequency is reduced the grounded electrode sheath region becomes electronegative. This strongly affects the electron power absorption dynamics and the discharge symmetry.
• Plasma assisted ignition with nanosecond surface dielectric barrier discharge. Two modes of nanosecond surface discharge
  
  • Shcherbanev S.A.
  • Popov N A
  • Starikovskaia Svetlana
  , 2016.
• Two Dimensional Particle-in-cell/Monte Carlo (PIC/MC) Simulation of Radio Frequency Capacitively Coupled Plasmas with a Dielectric Side Wall Boundary
  
  • Liu Yue
  • Booth Jean-Paul
  • Chabert Pascal
  , 2016. The majority of previous two dimensional (usually fluid) simulations of radio frequency capacitively coupled plasmas have focused on geometrically-asymmetric reactors (with a much larger grounded electrode than power electrode), which produces a strong dc self-bias. However, a commonly-used geometry comprises electrodes of equal area surrounded by a dielectric side wall, but this has not been widely simulated. We have developed a two dimensional (Cartesian) PIC/MC code based on the work of Hongyu Wang, Wei Jiang and Younian Wang, to simulate argon plasmas in this kind of chamber. Even using a thick dielectric, a peak in plasma density and electron power deposition is adjacent to the dielectric. The profiles of the electron and ion fluxes show that the period-averaged currents to the powered electrode are not locally balanced; the electron flux peaks closer to the dielectric edge, before dropping sharply. Finally, the effect of the dielectric thickness on the surface charge distribution and the angular distributions of ions arriving at boundaries is examined.
• Study of nanosecond discharges in different H2 air mixtures at atmospheric pressure for plasma assisted applications
  
  • Bourdon Anne
  • Kobayashi Sumire
  • Bonaventura Z.
  • Tholin Fabien
  • Popov N.A.
  , 2016.
• Reactive species in humidity containing atmospheric pressure plasma jets − Numerical and experimental investigations
  
  • Schröter Sandra
  • Bredin Jérôme
  • West A.
  • Dedrick J.
  • Niemi K.
  • Gibson Andrew
  • Foucher Mickaël
  • Booth Jean-Paul
  • de Oliveira N.
  • Joyeux D.
  • Nahon Laurent
  • Chechik V.
  • Wagenaars E.
  • Gans T.
  • O'Connell D.
  , 2016. The formation and absolute densities of oxygen and hydrogen containing reactive species such as atomic oxygen (O), hydrogen (H), hydroxyl radicals (OH) and hydrogen peroxide (H2O2) in an atmospheric pressure plasma jet (APPJ) are investigated as a function of the humidity content in the helium feed gas. APPJs are effective sources for these species, which are known to be biologically active and form a central role in their potential for biomedical applications. To develop and tailor APPJs for therapeutics, quantification of the reactive species produced is necessary. In this work, different diagnostic techniques, such as UV and VUV absorption spectroscopy and picosecond two-photon absorption laser-induced fluorescence (ps-TALIF) and a 0-dimensional chemical kinetics model are applied. We find that the densities of hydrogen containing species increase non-linearly with increasing feed gas humidity. The trend of atomic oxygen depends strongly on impurities present in the APPJ. The model results show that the dominant formation and destruction mechanisms of the species of interest are strongly influenced by the humidity content with different processes dominating at high and low humidity.
• Fast multipole and space adaptive multiresolution methods for the solution of the Poisson equation
  
  • Bilek P.
  • Duarte Max
  • Necas D.
  • Bourdon Anne
  • Bonaventura Z.
  , 2016.
• High-resolution TALIF measurements of atomic oxygen: determination of gas temperature and collisional broadening coefficients
  
  • Booth Jean-Paul
  • Marinov Daniil
  • Guaitella Olivier
  • Drag Cyril
  • Engeln Richard
  • Golda J.
  • Gathern V. Schultz-von Der
  , 2016. Two-photon Absorption Laser-Induced Fluorescence (TALIF) is a well-established technique to measure relative (and with appropriate calibration techniques, absolute) densities of atoms in plasmas and flames. The excitation line profiles can provide additional information, but this is usually overlooked due to the mediocre spectral resolution of commercial pulsed dye laser systems. We have investigated O-atom TALIF excitation line profiles using a house-built narrow line-width pulsed UV laser system, based on pulsed Ti:Sa ring laser seeded by a cw infrared diode laser. The observed Doppler profiles allow unambiguous measurement of gas temperature with high precision in O2 and CO2 DC glow discharges. Sub-Doppler measurements, performed by reflecting the laser beam back through excitation zone, allow the pressure-broadened line shapes to be observed, both in a pure O2 DC discharge (up to 10 Torr pressure) and in an atmospheric pressure RF plasma jet in He/O2. Pressure broadening coefficients of the 3p3PJ state of O were determined for O2 and He bath gases, and were found to be an order of magnitude bigger than that predicted from the measured quenching rate.
• Distinctive features of kinetics of plasma at high specific energy deposition
  
  • Lepikhin N D
  • Popov N A
  • Starikovskaia Svetlana
  , 2016.
• Measuring atomic oxygen densities and electron properties in an Inductively Coupled Plasma for thin film deposition
  
  • Meehan D.
  • Gibson Andrew
  • Booth Jean-Paul
  • Wagenaars E.
  , 2016. Plasma Enhanced Pulsed Laser Deposition (PE-PLD) is an advanced way of depositing thin films of oxide materials by using a laser to ablate a target, and passing the resulting plasma plume through a background Inductively-Coupled Plasma (ICP), instead of a background gas as is done in traditional PLD. The main advantage of PE-PLD is the control of film stoichiometry via the direct control of the reactive oxygen species in the ICP instead of relying on a neutral gas background. The aim is to deposit zinc oxide films from a zinc metal target and an oxygen ICP. In this work, we characterise the range of compositions of the reactive oxygen species achievable in ICPs; in particular the atomic oxygen density. The density of atomic oxygen has been determined within two ICPs of two different geometries over a range of plasma powers and pressures with the use of Energy Resolved Actinometry (ERA). ERA is a robust diagnostic technique with determines both the dissociation degree and average electron energy by comparing the excitation ratios of two oxygen and one argon transition. Alongside this the electron densities have been determined with the use of a hairpin probe.
• Plasma–liquid interactions: a review and roadmap
  
  • Bruggeman P
  • Kushner M
  • Locke B
  • Gardeniers J
  • Graham W
  • Graves B
  • Hofman-Caris M
  • Maric M
  • Reid P
  • Ceriani E.
  • Fernandez Rivas D
  • Foster J. Nathan
  • Garrick S
  • Gorbanev Y
  • Hamaguchi S
  • Iza F
  • Jablonowski J
  • Klimova E
  • Kolb J
  • Krcma F
  • Lukes P
  • Machala M
  • Marinov Ilya
  • Mariotti M
  • Mededovic Thagard M
  • Minakata M
  • Neyts E.
  • Pawlat P
  • Petrovic P
  • Pflieger Rachel
  • Reuter R
  • Schram D
  • Schröter S
  • Shiraiwa M
  • Tarabová B.
  • Tsai P
  • Verlet J
  • von Woedtke W
  • Wilson W
  • Yasui Y
  • Zvereva Z
  Plasma Sources Science and Technology, IOP Publishing, 2016, 25 (5), pp.053002. (10.1088/0963-0252/25/5/053002)
  DOI : 10.1088/0963-0252/25/5/053002
• SCALING OF COMPRESSIBLE MAGNETOHYDRODYNAMIC TURBULENCE IN THE FAST SOLAR WIND
  
  • Banerjee Supratik
  • Hadid Lina
  • Sahraoui Fouad
  • Galtier Sébastien
  The Astrophysical Journal Letters, Bristol : IOP Publishing, 2016, 829 (2), pp.L27. The role of compressible fluctuations in the energy cascade of fast solar wind turbulence is studied using a reduced form of an exact law derived recently for compressible isothermal magnetohydrodynamics and in situ observations from the THEMIS B/ARTEMIS P1 spacecraft. A statistical survey of the data revealed a turbulent energy cascade over a range of two decades of scales that is broader than the previous estimates made from an exact incompressible law. A term-by-term analysis of the compressible model reveals new insight into the role played by the compressible fluctuations in the energy cascade. The compressible fluctuations are shown to amplify by two to four times the turbulent cascade rate with respect to the incompressible model in~10% of the analyzed samples. This new estimated cascade rate is shown to provide the adequate energy dissipation required to account for the local heating of the non-adiabatic solar wind. (10.3847/2041-8205/829/2/l27)
  DOI : 10.3847/2041-8205/829/2/l27
• International school for students and young scientists Non-equilibrium and high-temperature gas flows
  
  • Starikovskaia Svetlana
  , 2016.
• Investigation de l'iode comme propergol pour la propulsion ionique à grilles
  
  • Grondein Pascaline
  , 2016. Le xénon est utilisé par la plupart des systèmes de propulsion électrique à grilles. Cependant sa rareté, son coût de production important ainsi que son usage dans de nombreuses applications industrielles font apparaître la nécessité de trouver une alternative à ce propergol. Il est apparu que l'iode était un candidat potentiel pour cela, étant beaucoup moins cher à produire et beaucoup moins rare. Il se présente sous forme de cristaux violacés dans les conditions standards de pression et de température et possède une pression de vaporisation peu élevée ainsi qu'un potentiel d'ionisation plus bas que celui du xénon. Un modèle global d'un plasma d'iode dans un propulseur électrique à grilles a donc été développé afin d'étudier le comportement et les performances d'un tel dispositif. Ces résultats de l'iode sont comparés à ceux du même dispositif obtenus par l'utilisation du xénon, les conditions d'opération étant bien évidemment similaires. Le modèle prédit une efficacité globale du propulseur 15% plus grande pour l'iode. Les résultats du modèle global en iode sont également comparés avec des résultats expérimentaux obtenus dans un propulseur électrique à grilles, sous des conditions d'opération et paramètres d'entrée similaires. Un band d'essai expérimental entièrement dédié à l'étude de l'iode comme nouveau propergol pour la propulsion à grilles a en effet été assemblé avec toutes les précautions nécessaires, l'iode étant un élément corrosif et chimiquement actif avec certains matériaux. Le banc d'essai en iode fut également utilisé pour effectuer la preuve de concept en iode du propulseur PEGASES.
• Impact des évènements solaires sur l'ionisation de l'ionosphère des moyennes et basses latitudes dans le secteur Europe-Afrique
  
  • Azzouzi Ilyasse
  , 2016. Ce travail a pour objet d’étudier les variations régulières de l’ionosphère aux moyennes et basses latitudes ainsi que l’impact de différents événements solaires sur l’ionisation. Pour quantifier ces variations, nous utiliserons les réseaux GPS qui permettent de mesurer le Contenu Total Electronique (TEC).Ce travail s’inscrit dans le cadre du projet ISWI. L’étude comprendra une analyse morphologique sur les variations régulières de l’ionisation en période de soleil calme (variation diurne, saisonnière et en fonction du cycle solaire) par le traitement de stations GPS en Europe et en Afrique sur la période analysée (2000 à 2014);les variations perturbées de l’ionosphère associées à des événements solaires retenus selon une grille de critères; L’analyse de l’indice ROTI afin d’étudier les scintillations ionosphériques génératrices d’une dégradation du positionnement aux basses latitudes et en particulier en Afrique.L’étude se poursuivra par la comparaison avec les modèles existants afin d’identifier leurs performances:le modèle NeQuick2, logiciel de modélisation du profil vertical médian l’ionosphère,Le modèle IONEX/CODG qui est une cartographie journalière du TEC en des positions spatiales et temporelles particulières et issu du post-traitement des mesures GPS sur une couverture mondiale.Le troisième volet de cette étude sera de donner des perspectives pour une éventuelle prévision de l’impact d'événements solaires particuliers sur l’ionosphère, par exemple la modélisation des gradients en période magnétiquement perturbée et la prévision de la présence du phénomène de scintillation ionosphérique sur certains trajets satellite-sol.
• TEC variations and ionospheric disturbances during the magnetic storm in March 2015 observed from continuous GPS data in the Southeast Asia region
  
  • Minh* Le Huy
  • Lan Tran Thi
  • Fleury Rolland
  • Amory-Mazaudier Christine
  • Thanh Le Truong
  • Thang Nguyen Chien
  • Thanh Nguyen Ha
  Vietnam Journal of Earth Sciences, Vietnam Academy of Science and Technology (VAST), 2016, 38 (3), pp.267 - 285. The paper presents a method for computing the ionospheric total electron content (TEC) using the combination of the phase and code measurements at the frequencies f1 and f2 of the global positioning system, and applies it to study the TEC variations and disturbances during the magnetic storm in March 2015 using GPS continuous data in the Southeast Asia region. The computation results show that the TEC values calculated by using the combination of phase and code measurements are less dispersed than the ones by using only the pseudo ranges. The magnetic storm whose the main phase was on the 17th March 2015, with the minimum value of the SYM/H index of -223 nT is the biggest during the 24th solar cycle. In the main phase, the crests of the equatorial ionization anomaly (EIA) expanded poleward with large increases of TEC amplitudes, that provides evidence of the penetration of the magnetospheric eastward electric field into the ionosphere and of the enhancement of the plasma fountain effect associated with the upward plasma drifts. In the first day of the recovery phase, due to the effect of the ionospheric disturbance dynamo, the amplitude of northern crest decreased an amount of about 25% with respect to an undisturbed day, and this crest moved equatorward a distance of about 11o, meanwhile the southern crest disappeared completely. In the main phase the ionospheric disturbances (scintillations) developed weakly, meanwhile in the first day of the recovery phase, they were inhibited nearly completely. During the storm time, in some days with low magnetic activity (Ap<~50 nT), the ionospheric disturbances in the local night-time were quite strong. The strong disturbance regions with ROTI > 0.5 concentrated near the crests of the EIA. The latitudinal-temporal TEC disturbance maps in these nights have been established. The morphology of these maps shows that the TEC disturbances are due to the medium-scale travelling ionospheric disturbances (MSTID) generated by acoustic-gravity waves in the northern crest region of the EIA after sunset moving equatorward with the velocity of about 210 m/s. (10.15625/0866-7187/38/3/8714)
  DOI : 10.15625/0866-7187/38/3/8714
• In-situ observations of compressible turbulence in planetary magnetosheaths and solar wind
  
  • Hadid Lina
  , 2016. Among the different astrophysical plasmas, the solar wind and the planetary magnetosheathsrepresent the best laboratories for studying the properties of fully developed plasma turbulence.Because of the relatively weak density fluctuations (∼ 10%) in the solar wind, the low frequencyfluctuations are usually described using the incompressible MHD theory. Nevertheless, the effectof the compressibility (in particular in the fast wind) has been a subject of active research withinthe space physics community over the last three decades.My thesis is essentially dedicated to the study of compressible turbulence in different plasma environments,the planetary magnetosheaths (of Saturn and Earth) and the fast and slow solar wind.This was done using in-situ spacecraft data from the Cassini, Cluster and THEMIS/ARTEMISsatellites.I first investigated the properties of MHD and kinetic scale turbulence in the magnetosheathof Saturn using Cassini data at the MHD scales and compared them to known features of thesolar wind turbulence. This work was completed with a more detailed analysis performed in themagnetosheath of Earth using the Cluster data. Then, by applying the recently derived exactlaw of compressible isothermal MHD turbulence to the in-situ observations from THEMIS andCLUSTER spacecrafts, a detailed study regarding the effect of the compressibility on the energycascade (dissipation) rate in the fast and the slow wind is presented. Several new empirical lawsare obtained, which include the power-law scaling of the energy cascade rate as function of theturbulent Mach number. Eventually, an application of this exact model to a more compressiblemedium, the magnetosheath of Earth, using the Cluster data provides the first estimation of theenergy dissipation rate in the magnetosheath, which is found to be up to two orders of magnitudehigher than that observed in the solar wind.
• Gas temperature measuements by high-resolution TALIF
  
  • Booth Jean-Paul
  , 2016. Two-photon Absorption Laser-Induced Fluorescence (TALIF) is a well-established technique to measure relative (and with appropriate calibration techniques, absolute) densities of atoms in plasmas and flames. The excitation line profiles can provide additional information, but this is usually overlooked due to the mediocre spectral resolution of commercial pulsed dye laser systems. We have investigated O-atom TALIF excitation line profiles using a house-built narrow line-width pulsed UV laser system, based on pulsed Ti:Sa ring laser seeded by a cw infrared diode laser. The observed Doppler profiles allow unambiguous measurement of gas temperature with high precision in O2 and CO2 DC glow discharges. Sub-Doppler measurements, performed by reflecting the laser beam back through excitation zone, allow the pressure-broadened line shapes to be observed, both in a pure O2 DC discharge (up to 10 Torr pressure) and in an atmospheric pressure RF plasma jet in He/O2. Pressure broadening coefficients of the 3p3PJ state of O were determined for O2 and He bath gases, and were found to be an order of magnitude bigger than that predicted from the measured quenching rate.