Publications

2018

• Advances in Electrodynamics during the three international projects : IEEY, IHY and ISWI
  
  • Amory-Mazaudier Christine
  • Doumbia V.
  , 2018.
• Turbulent dynamics of the solar wind
  
  • Montagud Camps Victor
  , 2018. The aim of this thesis is the study of the development of turbulence in the solar wind between 0.2 and 1 astronomical unit (AU) from the Sun (i.e. Earth’s orbit). The study is done by solving the magnetohydrodynamics equations (MHD) after subtracting the mean radial flow. The two aspects of turbulence that interest us are the 3D structure of the energy spectra and the heating of plasma that results from the turbulent dissipation of eddies and current layers transported by the wind. We want to determine which conditions of the plasma close to the Sun can result into what we observe at 1 AU. We have relatively detailed measurements of what happens between 0.3 and 1 AU. One important goal of this work is to determine if the physics present in the equations that are integrated (MHD) is sufficient to reproduce what is observed in this interval of distances. We introduce the context of our work in the first part. We give a summary of the physics concerning the solar wind and the solar corona, and the basic equations used to describe the solar wind plasma and an introduction to turbulence. Part 2 is dedicated to the study of anisotropy in the turbulent cascade, which characterizes 3D spectra. In the inertial range, in-situ measurements at 1 AU show complex figures for these spectra that we can interpret in several ways : numerical simulations allow to clear ambiguities. An important question is to know whether the Earth-Sun symmetry axis or the mean magnetic field axis is dominant.The third part focuses on turbulent heating in fast and slow winds. Between 0.3 and 1 AU, proton temperature decreases more slowly than expected, which requires a heating source. This source is supposed to be the continuous dissipation of eddies and current layers transported by the wind. To start with, we consider the simple case of Burgers equation, which is a one-dimensional model for shock formation. Thereupon, we switch to the 3-dimensional case, where we consider initial conditions appropriate for slow and fast winds. In the last part we expose our conclusions and propose the implementation of temperature anisotropy as future work.
• WEST first plasma operation with all tungsten PFC
  
  • Bucalossi J.
  • Bourdelle C.
  • Fedorczak N.
  • Loarer T.
  • Moreau P.
  • Tsitronne E.
  • Artaud J.-F.
  • Brezinsek S.
  • Bufferand H.
  • Courtois X.
  • Delpech L.
  • Desgranges C.
  • Devynck P.
  • Douai D.
  • Dumont R.
  • Ekedahl A.
  • Garcia J.
  • Garpar J.
  • Gil C.
  • Goniche M.
  • Gunn J.
  • Helou W.
  • Hennequin Pascale
  • Keppler C.
  • Maget P.
  • Marandet Y.
  • Mazon D.
  • Meyer O.
  • Morales J.
  • Nardon E.
  • Nouailletas R.
  • Peysson Y.
  • Reux Cedric
  • Saint-Laurent F.
  • Tamain P.
  • Vermare Laure
  • Vezinet D.
  • West Team The
  , 2018.
• Diagnostics of plasma neutral species in a very high frequency oxygen plasma with high sensitivity broadband absorption spectroscopy
  
  • Zhao J.
  • Ventzek Peter L G
  • Lane Barton
  • Iwao Toshihiko
  • Ishibashi Kiyotaka
  • Booth Jean-Paul
  , 2018.
• Lasers nanosecondes monomodes et TALIF (Two-photon Absorption Laser Induced Fluorescence)
  
  • Drag Cyril
  , 2018.
• Study of reduced kinetic models for plasma turbulence
  
  • Xu Shaokang
  , 2018. Turbulent transport is one of the keys to improve the energy confinement time required for thermonuclear fusion reactors. The description of the kinetic turbulence of the plasma is a problem with 3 spatial coordinates and 3 velocity coordinates. Both theory and simulation of a problem of such high dimensionality are very difficult, and reduced models are helpfull to understand turbulence in Tokamaks. A widely used technique consists into averaging the cyclotron motion, which is much faster than the turbulence time scale. Such a reduction makes it possible to simplify the problem to three spatial coordinates of the particle guide centers, a parallel velocity or energy, and a perpendicular velocity appearing as the adiabatic invariant. Nonlinear gyrokinetic description requires massively parallel high performance numerical simulations. The difficulty lies in the non-linear terms (Poisson hooks) that describe multi-scale interactions, which is a challenge for both theory and simulation. Any reduced approach, based on well-controlled hypotheses, is therefore interesting to develop.On the basis of this ambition, this thesis concerns the turbulence of particles trapped in magnetized plasma. It is a 4D system, obtained after averaging the particle distribution function on cyclotron and bounce motions, which can be considered as a reduced form of standard gyrokinetic theory. We called it "bounce averaged gyrokinetics" during this work. Even if this description is greatly reduced compared to the gyrokinetic theory, nonlinear direct simulation remains a challenge.A description of the nonlinear polar coordinate terms is chosen, with a logarithmic grid along the norm of the wave vector, while the angles are discretized on a regular grid. The use of a logarithmic grid makes it possible to take into account a wide range of wave vectors, so physics on a very small scale. In a similar way to shell models for fluid turbulence, and in order to simplify the system, only the interactions between neighboring shells are considered.In a first step, the study of the linear system is presented, in particular the paraetric dependence of the instability thresholds and the linear growth rate, allowing to recover the strong anisotropy of the growth rates of the trapped ion modes (or TIM) and the modes of trapped electrons (or TEM). These studies also make it possible to validate the non-linear numerical codes with respect to an independently developer eigenvalue solver.In a second step, the isotropic hypothesis for nonlinear terms is used. Thus, there is no exact phase information for such 1D layer models, which leaves with a free parameter in the interaction coefficients. An original power law is evidenced, which is unaffected by the value of the free parameter, measuring the intensity of the nonlinear effects relative to the linear terms.From the simulation of the isotropic model, the phase information appears very important. Since the linear instability is anisotropic for the fusion, the simulation of the anisotropic model is thus carried out in a third time. The numerically resolved system is reduced to a kinetic species, assuming that the other species are adiabatic. Two different systems can thus be studied: kinetic ions + adiabatic electrons and kinetic electrons + adiabatic ions. Different spectra are observed in each of these two cases, and the validity of the adiabatic hypothesis is discussed for each species, based on a kinetic simulation with two species.
• Sun-Earth System : Signatures of the components of the solar magnetic field on the Earth's magnetic field
  
  • Amory-Mazaudier Christine
  , 2018.
• Etat de l'art des simulations HPC de processus eruptifs
  
  • Smets Roch
  • Aunai Nicolas
  , 2018.
• IonSat: challenging the atmospheric drag with a 6U nanosatellite
  
  • Pellouin Clément
  • Marmuse Florian
  • Chakrani Jafaar
  • Hurot Thomas
  • Lequette Nicolas
  • Magda Geoffrey
  • Tommasini Augustin
  • Toussaint Arthur
  • Yang Clément
  • Solovyeva Lilia
  , 2018. Herein, we present a feasibility study and a mission design for a 6U CubeSat propelled by an iodine NPT-30i miniaturized thruster from the company ThrustMe, to be ready for launch in the early 2020s. The project is led by École polytechnique, Palaiseau, France and supported by the French space agency CNES. The phase A study shows that the stand-alone propulsion system can be embedded in a 6U CubeSat and be used in the frame of a coherent mission over more than a year, under the condition of integrating a low-requirements payload, mainly in terms of volume. Deployable solar generators, aerobraking strategies and large battery capacities allow the satellite to perform orbit changes and station-keeping at 300km from any orbit inclination. This mission aims to demonstrate a long-duration station-keeping at low altitude and to assess the suitability of electric propulsion devices for tightly constrained missions such as student CubeSats. As part of the phase A study, the design of an attitude control system relevant to orbit changes is presented, as well as a first thermal analysis of a 6U CubeSat able to generate more than 50W of power. The mission analysis is also explicated: it led to the unusual choice of a spacecraft able to tackle most orbits, at the cost of an adaptation of the mission plan. The general resulting structure and subsystems integration to comply with such constraints is also presented. It is designed to compromise between aerodynamics and total power supply with deployable solar panels and a displaced centre of mass. This feasibility study tends to show that propulsion for SmallSats is available and has reached milestones in terms of costs and ease of integration that make it compatible with university projects. It is also shown that a 6U CubeSat can today be suitable for a mission needing an electric power subsystem, providing the payload does not have demanding power or volume requirements.
• Kinetic simulation of magnetic field generation and collisionless shock formation in expanding laboratory plasmas
  
  • Fox W.
  • Matteucci J.
  • Moissard C.
  • Schaeffer D.
  • Bhattacharjee A.
  • Germaschewski K.
  • Hu S.
  Physics of Plasmas, American Institute of Physics, 2018, 25 (10), pp.102106. (10.1063/1.5050813)
  DOI : 10.1063/1.5050813
• Whistler envelope solitons. I. Dynamics in inhomogeneous plasmas
  
  • Krafft C.
  • Volokitin A.S.
  Physics of Plasmas, American Institute of Physics, 2018, 25 (10), pp.102301. A self-consistent Hamiltonian model based on equations describing the coupled dynamics of whistler and lower frequency waves in inhomogeneous plasmas is built. On this basis, different aspects of whistler turbulence are studied, concerning mainly the development of modulational instabilities and the dynamics of envelope solitons in irregular plasmas. Numerical simulations based on the model show that modulational instabilities can lead to the generation of a beating of stable nonlinear whistlers propagating with a speed near the group velocity. The whistler envelope soliton is determined analytically, and its propagation in plasmas presenting random density fluctuations and weakly irregular density structures of different scales and amplitudes is studied, showing that the envelope is very weakly affected by these inhomogeneities, whereas the wavelengths and the amplitudes of the phase oscillations strongly vary. Moreover, simulations show for the first time that two whistler solitons moving with different but close velocities and colliding one with the other remain unchanged after this collision, independently of their initial amplitudes and velocities. Finally, we study the dynamics of sonic whistler envelope solitons and show that the propagation of their lower frequency perturbation is governed by a KdV-type equation. (10.1063/1.5041055)
  DOI : 10.1063/1.5041055
• Collision risk prediction for constellation operators
  
  • Lucken Romain
  • Giolito Damien
  , 2018. INDEMN is an object-oriented Python program dedicated to the modeling of the evolution of the densities of space objects. Following the work achieved by G. L. Somma (IAC 2016), the dynamical model is based on a source and sink approach for various altitudes. The source terms represent the future launches, the explosion of intact spacecrafts, and the collision between objects. Different collision cross sections are used for the various types of objects and the number of debris generated is based on the NASA break-up model. The sink terms are the drag and the end-of-life de-orbitation for the satellites launched after 2009, with a controllable success rate. The code was validated using the benchmark released by the Inter-Agency Space Debris Coordination Committee on the Stability of the Future LEO environment (IADC-12-08, Rev. 1, 2013). In addition to the classical object types featured in several statistical codes, which are intact objects, explosion debris, and collision debris, a new type representing the satellites of a specific constellation is included. These satellites orbit with altitudes close to 1 200 km and they can perform collision avoidance maneuvers as long as they are fully operational. It is shown that if only one primary collision occurs, the risk of a collision involving a constellation satellite becomes larger than 5% by 2035, which highly jeopardizes the satellite constellation as a whole.
• Vacuum ultraviolet absorption spectroscopy of oxygen discharges
  
  • Booth Jean-Paul
  • Chatterjee Abhyuday
  • Guaitella Olivier
  • de Oliveira N.
  • Nahon L.
  • Lopaev Dmitry
  • Zyryanov Sergey
  • Western Colin
  , 2018.
• Experimental study of ammonia formation in Titan's ionosphere
  
  • Chatain Audrey
  • Carrasco Nathalie
  • Guaitella Olivier
  • Napoleoni Maryse
  • Vettier Ludovic
  • Cernogora Guy
  , 2018. Ammonia is an interesting molecule suspected to be formed in Titan ionosphere and leading to further complex chemistry. Here we experimentally study one of the two ways of formation of ammonia in the ionosphere: the catalysis on surfaces in a N2-H2 plasma. We vary plasma conditions in a CCP RF discharge and follow the ammonia formation thanks to IR and mass spectrometries. We show the strong effect of pressure, H2 percentage, plasma power and metallic surfaces.
• Local Excitation of Whistler Mode Waves and Associated Langmuir Waves at Dayside Reconnection Regions
  
  • Li Jinxing
  • Bortnik Jacob
  • An Xin
  • Li Wen
  • Russell Christopher
  • Zhou Meng
  • Berchem Jean
  • Zhao Cong
  • Wang Shan
  • Torbert Roy
  • Le Contel Olivier
  • Ergun Robert
  • Lindqvist Per-Arne
  • Pollock Craig
  • Burch James
  Geophysical Research Letters, American Geophysical Union, 2018, 45 (17), pp.8793-8802. (10.1029/2018GL078287)
  DOI : 10.1029/2018GL078287
• Detection and dynamics of Martian plasma boundaries
  
  • Garnier P.
  • Ecoffet D.
  • Génot V.
  • Aunai Nicolas
  • Nguyen Gautier
  • Mazelle C.
  • Fang X.
  • Hall Benjamin
  • Masunaga Kei
  , 2018.
• Cometary plasma response to interplanetary corotating interaction regions during 2016 June - September: a quantitative study by the Rosetta Plasma Consortium
  
  • Hajra Rajkumar
  • Henri Pierre
  • Myllys Minna
  • Heritier Kevin
  • Galand Marina
  • Simon Wedlund Cyril
  • Breuillard Hugo
  • Behar Etienne
  • Edberg Niklas
  • Goetz Charlotte
  • Nilsson Hans
  • Eriksson Anders
  • Goldstein Raymond
  • Tsurutani Bruce
  • More Jerome
  • Vallieres Xavier
  • Wattieaux Gaetan
  , 2018, pp.18 pp.. Four interplanetary corotating interaction regions (CIRs) were identified during 2016 June through September by the Rosetta Plasma Consortium (RPC) monitoring in situ the plasma environment of the comet 67P/Churyumov-Gerasimenko (67P) at the heliocentric distances of 3 and 3.8 au. The CIRs, formed in the interface region between low- and high-speed solar wind streams with speeds of 320-400 km s-1 and ∼580-640 km s-1 respectively, are characterized by relative increases in solar wind proton density by ∼13-29, in proton temperature by ∼7-29, and in magnetic field by ∼1-4 with respect to the pre-CIR values. The CIR boundaries are well-defined with interplanetary discontinuities. Out of 10 interplanetary discontinuities at the CIR boundaries, 4 are determined to be forward waves and 5 are reverse waves, propagating at ∼5-92% of the magnetosonic speed at angles of ∼19.8°-86.6° relative to ambient magnetic field. Only one is identified to be a quasi-parallel forward shock with magnetosonic Mach number of 1.48 and shock normal angle of 41.0°. The response of the cometary ionosphere was monitored by Rosetta from cometocentric distances of ∼4 to 30 km. A quiet time plasma density map was developed by considering the effects of varying cometary latitude, longitude and cometocentric distance of the Rosetta observations before and after each of the CIR intervals. The CIRs lead to plasma density enhancements of ∼500-1000% with respect to the quiet time reference level. Ionospheric modeling shows that increased ionization rate due to enhanced ionizing suprathermal (>12-200 eV) electron impact is the prime cause of the large cometary plasma density enhancements during the CIRs. Plausible origin mechanisms of the cometary suprathermal electron enhancements are discussed.
• Evolution of organic aerosols under conditions similar to Titan's ionosphere
  
  • Chatain Audrey
  • Carrasco Nathalie
  • Guaitella Olivier
  • Ruscassier N.
  , 2018, 12, pp.EPSC2018-200-1 (2p.). Titan's ionosphere is a dusty plasma where complex organic aerosols are formed. As they have a strong prebiotic interest, we would like to understand how they are formed and how they interact with the surrounding plasma. Here we simulate this interaction dust-plasma in a DC reactor. We place analogues of Titan's aerosols in a N2-H2 discharge and follow their infrared absorption spectrum all along the exposure. The evolution of the surface state of the sample is also observed by scanning electron microscopy. First experiments indicate some modifications in the absorption bands and in the surface structure. Therefore, the organic aerosols seem to be physically and chemically altered by the plasma.
• Intense Electric Fields and Electron-Scale Substructure Within Magnetotail Flux Ropes as Revealed by the Magnetospheric Multiscale Mission
  
  • Stawarz J.
  • Eastwood J.
  • Genestreti K.
  • Nakamura R.
  • Ergun R.
  • Burgess D.
  • Burch J.
  • Fuselier S.
  • Gershman D.
  • Giles B.
  • Le Contel O.
  • Lindqvist P.-A.
  • Russell C.
  • Torbert R.
  Geophysical Research Letters, American Geophysical Union, 2018, 45 (17), pp.8783-8792. (10.1029/2018GL079095)
  DOI : 10.1029/2018GL079095
• Coexistence of Weak and Strong Wave Turbulence in Incompressible Hall Magnetohydrodynamics
  
  • Meyrand Romain
  • Kiyani K. H.
  • Gürcan Özgur D.
  • Galtier Sébastien
  Physical Review X, American Physical Society, 2018, 8 (3), pp.031066. We report a numerical investigation of three-dimensional, incompressible, Hall magnetohydrodynamic turbulence with a relatively strong mean magnetic field. Using helicity decomposition and cross-bicoherence analysis, we observe that the resonant three-wave coupling is substantial among ion-cyclotron and whistler waves. A detailed study of the degree of nonlinearity of these two populations shows that the ion-cyclotron component experiences a transition from weak to strong wave turbulence going from large to small scales, while the whistler fluctuations display a weak wave turbulence character for all scales. This nontrivial coexistence of the two regimes with two populations of waves gives rise to anomalous anisotropy and scaling properties. The weak and strong wave turbulence components can be distinguished rather efficiently using spatiotemporal Fourier transforms. The analysis shows that while resonant triad interactions survive the highly nonlinear bath of ion-cyclotron fluctuations at large scales for which the degree of nonlinearity is low for both populations of waves, whistler waves tend to be killed by the nonlinear cross-coupling at smaller scales where the ion-cyclotron component is in the strong wave turbulent regime. Such a situation may have far-reaching implications for the physics of magnetized turbulence in many astrophysical and space plasmas and probably beyond, where different waves coexist and compete to transfer energy nonlinearly, across scales. (10.1103/PhysRevX.8.031066)
  DOI : 10.1103/PhysRevX.8.031066
• What can we gain from laboratory experiments in studying space plasma processes
  
  • Smets Roch
  • Fuchs J. C.
  • Sladkov Andrey
  • Aunai Nicolas
  , 2018.
• Barrier discharge and pulsed discharge modelling
  
  • Bourdon Anne
  , 2018.
• Investigation of key plasma species on germination boosting of Mung bean
  
  • Liu Bo
  • Yang Hang
  • Honnorat Bruno
  • Rousseau Antoine
  , 2018. Atmospheric-pressure dielectric barrier discharge (DBD) plasma array has been used to treat mung bean seeds and mustard to explore the responses of them in terms of germination rate under direct and indirect plasma treatment methods. Plasma stimulation could selectively affect germination of mung bean and mustard seeds. Plasma indirect treatment showed a positive germination promotion both in mung bean and mustard seeds, while plasma direct treatment only increased mung bean germination rate, inhibit that of mustard. This enhancement of germination was related with plasma produced activated ions both including long life ions and short life oxidative radicals in liquid condition. Short life radicals, e.g. hydroxyl radical etc, played a more sensitive promoting effect because of their stronger chemical and biological activities.
• The legacy of Cassini RPWS: Radio and plasma wav es at Saturn
  
  • Kurth William S.
  • Gurnett Donald A.
  • Averkamp T. F.
  • Bostrom R.
  • Canu Patrick
  • Cecconi B.
  • Cornilleau-Wehrlin Nicole
  • Farrell William M.
  • Fischer G.
  • Galopeau Patrick H. M.
  • Gustafsson G.
  • Hadid Lina
  • Hospodarsky George B.
  • Lamy Laurent
  • Lecacheux Alain
  • Louarn P.
  • Macdowall R. J.
  • Menietti J. D.
  • Modolo Ronan
  • Morooka M.
  • Pedersen A.
  • Persoon A. M.
  • Sulaiman A.
  • Wahlund J. E.
  • Ye S.
  • Zarka P.
  , 2018. Introduction: The 13 - year exploration of Saturn with Cassini provided enormous scientific return from the Radio and P lasma Wave Science (RPWS) investigation. While it is not possible to achieve absolute concensus on the most important results from this investigation, here we attempt to show the breadth of contributions to the study of the Saturnian system with this inst rument. Saturn Kilometric Radiation: Cassini’s RPWS determined that not only does the SKR rotational modulation vary in time, there are typically two different periods in the northern and southern hemispheres. Cassini crossed the SKR source region, conf irming that the cyclotron maser instability (CMI) can drive the auroral radio emissions. These are the first in situ observations of a n on - terrestrial CMI radio source. In addition, SKR was shown to be generated on field lines threading the UV auroras an d diagnositic of magnetospheric dynamics imposed by solar wind compressions and tail reconnection. Enceladus and the E ring: RPWS observations contributed to the mapping of dust from the plumes of Enceladus and the resulting E ring. The discovery of aur oral hiss generated by electron beams accelerated from the moon informed our understanding of the electromagnetic interaction of the moon with the magnetosphere. Auroal hiss also provided evidence of this interaction ve ry close to the planet on field lines threading the moon. Plasma resulting from the ionoization of material coming from Enceladus was modeled through the determination of the electron density in Saturn’s inner magnetosphere. The depletion of the electron den sity in the plume led to the real ization that charged micron - sized dust grains were a major component of a dusty plasma in the vicinity of the moon. Lightning: High frequency radio emissions initiated in lightning strokes enabled RPWS to characterize the occurrence of lightning, hence, c onvective storms in Saturn’s atmosphere and tracked the development of a Great White Spot storm beginning in late 2010. Coupled with amateur and ISS images, an extensive compilation of thunderstorm activity in Saturn’s atmosphere was poss ible. Titan’s Ion osphere: The RPWS Langmuir Probe was the first instrument to confirm the existence of a substantial ionosphere at Titan. The Solar EUV dominates the ionization of the upper atmosphere of Titan, although energetic particles in Saturn’s magnetosphere do con tribute substantially at all Solar Zenith Angles . Observations over the orbital mission showed the effect of the vaiation of EUV over the solar cycle in the ionospheric density. One of the more intriguing discoveries was the formation of complex negative organic ions and aerosol pre - cursors in the deep ionosphere of Titan, which may have implications for how pre - biotic chemistry occurred on the early Earth. RPWS observations also helped characterize the interaction of Titan with the solar wind and the deve lopment of a compound bowshock encompassing both Titan and Saturn’s magnetosphere. Saturn’s Ionosphere: An obvious result of Cassini’s Grand Finale was the first in situ obervations of electron densities and temperatures in Saturn’s topside ionosphere and the revelation of strong interactions between the rings and the ionosphere.
• Evolution of aerosols in Titan’s ionospheric plasma: An experimental simulation
  
  • Chatain Audrey
  • Guaitella Olivier
  • Carrasco Nathalie
  • Ruscassier N.
  , 2018. Observatio ns by the space mission Cassini have revealed the formation of complex organic molecules in Titan ’s ionosphere. To better understand this complex chemistry, several experiments were conducted to reproduce analogs of Titan ’s aerosols in laboratories, named ‘tholins’. These tholins appear to be polymeric and nitrogenous molecules . Aerosols stay many years in Titan ’s upper atmosphere, a dusty plasma where molecules are continuously bombarded by charged molecules. Consequently, they are likely to evolve during their stay. Here we address this question by experimental simulation: we analyze the effect of harsh plasma environment on tholins alread y formed. o separate the processes of formation and evolution, aerosols samples used are first formed with the experiment PAMPRE at LATMOS [ T Gautier Icarus 2016 ]. T hen tholins are prepared in the shape of thin pellets and positi oned at the center of a plasma reactor, where they are exposed during several hours in a DC N 2 - H 2 glow discharge, partially representative of Titan’s ionosphere. Methane is purposefully removed from this second phase to prevent the formation of new aerosol s. Morphological changes. Pellets become rougher during the exposure. Surface structure is observed through a Scanning Electron Microscope before and after an exposure of four hours. It shows that plasma sputteri ng attacks the surface and removes some material. Chemical modifications. We perform in situ infrared transmission spectroscopy during the exposure. Characteristic absorption bands of tholins are distorted, witnessing changes in the samples chemical struc ture. Especially, we suspect C - H bond environment to be complexed. Nitrile functions are also modified.