Publications

2021

• The Evolution of Compressible Solar Wind Turbulence in the Inner Heliosphere: PSP, THEMIS, and MAVEN Observations
  
  • Andrés N.
  • Sahraoui Fouad
  • Hadid L. Z.
  • Huang S.
  • Romanelli N.
  • Galtier Sebastien
  • Dibraccio G.
  • Halekas J.
  The Astrophysical Journal, American Astronomical Society, 2021, 919 (1), pp.19. (10.3847/1538-4357/ac0af5)
  DOI : 10.3847/1538-4357/ac0af5
• BepiColombo’s Cruise Phase: Unique Opportunity for Synergistic Observations
  
  • Hadid L. Z.
  • Génot V.
  • Aizawa S.
  • Milillo A.
  • Zender J.
  • Murakami G.
  • Benkhoff J.
  • Zouganelis I.
  • Alberti T.
  • André N.
  • Bebesi Z.
  • Califano F.
  • Dimmock A.
  • Dosa M.
  • Escoubet C.
  • Griton L.
  • Ho G.
  • Horbury T.
  • Iwai K.
  • Janvier M.
  • Kilpua E.
  • Lavraud B.
  • Madar A.
  • Miyoshi Y.
  • Müller D.
  • Pinto R.
  • Rouillard A.
  • Raines J.
  • Raouafi N.
  • Sahraoui F.
  • Sánchez-Cano B.
  • Shiota D.
  • Vainio R.
  • Walsh A.
  Frontiers in Astronomy and Space Sciences, Frontiers Media, 2021, 8. The investigation of multi-spacecraft coordinated observations during the cruise phase of BepiColombo (ESA/JAXA) are reported, with a particular emphasis on the recently launched missions, Solar Orbiter (ESA/NASA) and Parker Solar Probe (NASA). Despite some payload constraints, many instruments onboard BepiColombo are operating during its cruise phase simultaneously covering a wide range of heliocentric distances (0.28 AU–0.5 AU). Hence, the various spacecraft configurations and the combined in-situ and remote sensing measurements from the different spacecraft, offer unique opportunities for BepiColombo to be part of these unprecedented multipoint synergistic observations and for potential scientific studies in the inner heliosphere, even before its orbit insertion around Mercury in December 2025. The main goal of this report is to present the coordinated observation opportunities during the cruise phase of BepiColombo (excluding the planetary flybys). We summarize the identified science topics, the operational instruments, the method we have used to identify the windows of opportunity and discuss the planning of joint observations in the future. (10.3389/fspas.2021.718024)
  DOI : 10.3389/fspas.2021.718024
• Flattening of the Density Spectrum in Compressible Hall-MHD Simulations
  
  • Montagud-Camps Victor
  • Němec František
  • Šafránková Jana
  • Němeček Zdeněk
  • Verdini Andrea
  • Grappin Roland
  • Papini Emanuele
  • Franci Luca
  Atmosphere, MDPI, 2021, 12 (9), pp.1162. Observations of proton density fluctuations of the solar wind at 1 au have shown the presence of a decade-long transition region of the density spectrum above sub-ion scales, characterized by a flattening of the spectral slope. We use the proton density fluctuations data collected by the BMSW instrument on-board the Spektr-R satellite in order to delimit the plasma parameters under which the transition region can be observed. Under similar plasma conditions to those in observations, we carry out 3D compressible magnetohydrodynamics (MHD) and Hall-MHD numerical simulations and find that Hall physics is necessary to generate the transition region. The analysis of the kω power spectrum in the Hall-MHD simulation indicates that the flattening of the density spectrum is associated with fluctuations having frequencies smaller than the ion cyclotron frequency. (10.3390/atmos12091162)
  DOI : 10.3390/atmos12091162
• Impact of non-axisymmetric magnetic field perturbations on flows
  
  • Varennes R
  • Garbet X
  • Vermare L
  • Sarazin Y
  • Grandgirard V
  • Dif-Pradalier Guilhem
  • Peret M
  , 2021.
• Magnetic reconnection leading to a mini-flare and a twisted jet observed with IRIS
  
  • Joshi Reetika
  • Schmieder Brigitte
  • Chandra Ramesh
  • Heinzel Petr
  • Aulanier Guillaume
  • Bommier Véronique
  • Tomin James
  • Vilmer Nicole
  , 2021.
• A model of interchange turbulent transport across separatrix with sheared flows
  
  • Peret Mathieu
  • Fedorczak Nicolas
  • Vermare Laure
  • Ramisch M
  • Schmid B
  , 2021.
• Impacts of Ionospheric Ions on Magnetic Reconnection and Earth's Magnetosphere Dynamics
  
  • Toledo-Redondo S.
  • André M.
  • Aunai N.
  • Chappell C.
  • Dargent J.
  • Fuselier S.
  • Glocer A.
  • Graham D.
  • Haaland S.
  • Hesse M.
  • Kistler L.
  • Lavraud B.
  • Li W.
  • Moore T.
  • Tenfjord P.
  • Vines S.
  Reviews of Geophysics, American Geophysical Union, 2021, 59 (3). Ionospheric ions (mainly H+, He+, and O+) escape from the ionosphere and populate the Earth's magnetosphere. Their thermal energies are usually low when they first escape the ionosphere, typically a few electron volt to tens of electron volt, but they are energized in their journey through the magnetosphere. The ionospheric population is variable, and it makes significant contributions to the magnetospheric mass density in key regions where magnetic reconnection is at work. Solar wind—magnetosphere coupling occurs primarily via magnetic reconnection, a key plasma process that enables transfer of mass and energy into the near-Earth space environment. Reconnection leads to the triggering of magnetospheric storms, auroras, energetic particle precipitation and a host of other magnetospheric phenomena. Several works in the last decades have attempted to statistically quantify the amount of ionospheric plasma supplied to the magnetosphere, including the two key regions where magnetic reconnection occurs: the dayside magnetopause and the magnetotail. Recent in situ observations by the Magnetospheric Multiscale spacecraft and associated modeling have advanced our current understanding of how ionospheric ions alter the magnetic reconnection process, including its onset and efficiency. This article compiles the current understanding of the ionospheric plasma supply to the magnetosphere. It reviews both the quantification of these sources and their effects on the process of magnetic reconnection. It also provides a global description of how the ionospheric ion contribution modifies the way the solar wind couples to the Earth's magnetosphere and how these ions modify the global dynamics of the near-Earth space environment. (10.1029/2020RG000707)
  DOI : 10.1029/2020RG000707
• Upper‐Hybrid Waves Driven by Meandering Electrons Around Magnetic Reconnection X Line
  
  • Li W.‐y.
  • Khotyaintsev Yu
  • Tang B.‐b.
  • Graham D.
  • Norgren C.
  • Vaivads A.
  • André M.
  • Le A.
  • Egedal J.
  • Dokgo K.
  • Fujimoto K.
  • He J.‐s.
  • Burch J.
  • Lindqvist P.‐a.
  • Ergun R.
  • Torbert R.
  • Le Contel O.
  • Gershman D.
  • Giles B.
  • Lavraud B.
  • Fuselier S.
  • Plaschke F.
  • Russell C.
  • Guo X.‐c.
  • Lu Q.‐m.
  • Wang C.
  Geophysical Research Letters, American Geophysical Union, 2021, 48 (16). (10.1029/2021GL093164)
  DOI : 10.1029/2021GL093164
• Characterization of ionospheric irregularities over Vietnam and adjacent region for the 2008-2018 period
  
  • Nguyen Thanh Dung
  • Le Huy Minh
  • Amory-Mazaudier Christine
  • Fleury Rolland
  • Saito Susumu
  • Nguyen Chien Thang
  • Pham Thi Thu Hong
  • Le Truong Thanh
  • Nguyen Thi Mai
  Vietnam Journal of Earth Sciences, Vietnam Academy of Science and Technology (VAST), 2021. This paper presents the variations of the rate of change of Total Electron Content (TEC) index (ROTI), characterizing the occurrence of ionospheric plasma irregularities over Vietnam and neighboring countries in the Southeast Asian region using the continuous GPS data during the 2008-2018 period. The results showed that the occurrence of strong ROTI in all stations is maximum in equinox months March/April and September/October and depends on solar activity. The ROTI is weak during periods of low solar activity and strong during periods of high solar activity. There is an asymmetry between the two equinoxes. During maximum and declining phases of 2014-2016, occurrence rates in March equinox are larger than in September equinox, but during the descending period of 2010-2011, the occurrence rates in September equinox at almost all stations are larger than in March equinox. The correlation coefficients between the monthly occurrence rate of irregularities and the F10.7 solar index at the stations in the equatorward EIA crest region are higher than at those in the magnetic equatorial and the poleward EIA crest regions. The irregularity occurrence is high in the pre-midnight sector, maximum between 2000 LT to 2200 LT. The maximum irregularity occurrence is located around 4-5° degrees in latitude equator-ward away from the anomaly crests. (10.15625/2615-9783/16502)
  DOI : 10.15625/2615-9783/16502
• The Plasma Observatory: exploring particle energization in space plasmas through multi-point, multi-scale in situ measurements
  
  • Retino A.
  , 2021.
• Magnetic Helicity Estimations in Models and Observations of the Solar Magnetic Field. IV. Application to Solar Observations
  
  • Thalmann J. K. K
  • Georgoulis M. K. K
  • Liu Y.
  • Pariat Etienne
  • Valori G.
  • Anfinogentov S.
  • Chen F.
  • Guo Y.
  • Moraitis K.
  • Yang S.
  • Mastrano Alpha
  The Astrophysical Journal, American Astronomical Society, 2021, 922 (1), pp.41. In this ISSI-supported series of studies on magnetic helicity in the Sun, we systematically implement different magnetic helicity calculation methods on high-quality solar magnetogram observations. We apply finite-volume, discrete flux tube (in particular, connectivity-based) and flux-integration methods to data from Hinode's Solar Optical Telescope. The target is NOAA active region 10930 during a 1.5 day interval in December 2006 that included a major eruptive flare (SOL2006-12-13T02:14X3.4). Finite-volume and connectivity-based methods yield instantaneous budgets of the coronal magnetic helicity, while the flux-integration methods allow an estimate of the accumulated helicity injected through the photosphere. The objectives of our work are twofold: A cross-validation of methods, as well as an interpretation of the complex events leading to the eruption. To the first objective, we find (i) strong agreement among the finite-volume methods, (ii) a moderate agreement between the connectivity-based and finite-volume methods, (iii) an excellent agreement between the flux-integration methods, and (iv) an overall agreement between finite-volume and flux-integration based estimates regarding the predominant sign and magnitude of the helicity. To the second objective, we are confident that the photospheric helicity flux significantly contributed to the coronal helicity budget, and that a right-handed structure erupted from a predominantly left-handed corona during the X-class flare. Overall, we find that the use of different methods to estimate the (accumulated) coronal helicity may be necessary in order to draw a complete picture of an active-region corona, given the careful handling of identified data (preparation) issues, which otherwise would mislead the event analysis and interpretation. (10.3847/1538-4357/ac1f93)
  DOI : 10.3847/1538-4357/ac1f93
• Second Harmonic Electromagnetic Emissions by an Electron Beam in Solar Wind Plasmas with Density Fluctuations
  
  • Krafft C.
  • Savoini P.
  The Astrophysical Journal Letters, Bristol : IOP Publishing, 2021, 917 (2), pp.L23. (10.3847/2041-8213/ac1795)
  DOI : 10.3847/2041-8213/ac1795
• Exploring solar-terrestrial interactions via multiple imaging observers
  
  • Branduardi-Raymont G.
  • Berthomier Matthieu
  • Bogdanova Y.
  • Carter J.
  • Collier M.
  • Dimmock A.
  • Dunlop M.
  • Fear R.
  • Forsyth C.
  • Hubert B.
  • Kronberg Elena
  • Laundal K.
  • Lester M.
  • Milan S.
  • Oksavik K.
  • Østgaard N.
  • Palmroth M.
  • Plaschke Ferdinand
  • Porter F.
  • Rae I.
  • Read A.
  • Samsonov A.
  • Sembay S.
  • Shprits Y.
  • Sibeck D.
  • Walsh B.
  • Yamauchi M.
  Experimental Astronomy, Springer Link, 2021, 54 (2-3), pp.361-390. How does solar wind energy flow through the Earth’s magnetosphere, how is it converted and distributed? is the question we want to address. We need to understand how geomagnetic storms and substorms start and grow, not just as a matter of scientific curiosity, but to address a clear and pressing practical problem: space weather, which can influence the performance and reliability of our technological systems, in space and on the ground, and can endanger human life and health. Much knowledge has already been acquired over the past decades, particularly by making use of multiple spacecraft measuring conditions in situ, but the infant stage of space weather forecasting demonstrates that we still have a vast amount of learning to do. A novel global approach is now being taken by a number of space imaging missions which are under development and the first tantalising results of their exploration will be available in the next decade. In this White Paper, submitted to ESA in response to the Voyage 2050 Call, we propose the next step in the quest for a complete understanding of how the Sun controls the Earth’s plasma environment: a tomographic imaging approach comprising two spacecraft in highly inclined polar orbits, enabling global imaging of magnetopause and cusps in soft X-rays, of auroral regions in FUV, of plasmasphere and ring current in EUV and ENA (Energetic Neutral Atoms), alongside in situ measurements. Such a mission, encompassing the variety of physical processes determining the conditions of geospace, will be crucial on the way to achieving scientific closure on the question of solar-terrestrial interactions. (10.1007/s10686-021-09784-y)
  DOI : 10.1007/s10686-021-09784-y
• Aerosols-plasma interaction in the ionosphere of Titan
  
  • Chatain Audrey
  • Carrasco Nathalie
  • Vettier Ludovic
  • Guaitella Olivier
  , 2021.
• Optical Photothermal Infrared Microspectroscopy Discriminates for the First Time Different Types of Lung Cells on Histopathology Glass Slides
  
  • Kansiz Mustafa
  • Dowling Lewis
  • Yousef Ibraheem
  • Guaitella Olivier
  • Borondics Ferenc
  • Sulé-Suso Josep
  Analytical Chemistry, American Chemical Society, 2021, 93 (32), pp.11081-11088. (10.1021/acs.analchem.1c00309)
  DOI : 10.1021/acs.analchem.1c00309
• Cluster Observations of Energetic Electron Acceleration Within Earthward Reconnection Jet and Associated Magnetic Flux Rope
  
  • Vaivads A.
  • Khotyaintsev Yu.
  • Retinò A.
  • Fu H.
  • Kronberg E.
  • Daly P.
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2021, 126 (8). (10.1029/2021JA029545)
  DOI : 10.1029/2021JA029545
• Non-equilibrium plasma for ignition and combustion enhancement
  
  • Starikovskaia Svetlana
  • Lacoste Deanna
  • Colonna Gianpiero
  The European Physical Journal D : Atomic, molecular, optical and plasma physics, EDP Sciences, 2021, 75 (8), pp.231. (10.1140/epjd/s10053-021-00240-2)
  DOI : 10.1140/epjd/s10053-021-00240-2
• Pre-flight Calibration and Near-Earth Commissioning Results of the Mercury Plasma Particle Experiment (MPPE) Onboard MMO (Mio)
  
  • Saito Yoshifumi
  • Delcourt Dominique
  • Hirahara Masafumi
  • Barabash Stas
  • André Nicolas
  • Takashima Takeshi
  • Asamura Kazushi
  • Yokota Shoichiro
  • Wieser Martin
  • Nishino Masaki
  • Oka Mitsuo
  • Futaana Yoshifumi
  • Harada Yuki
  • Sauvaud Jean-André
  • Louarn Philippe
  • Lavraud Benoit
  • Génot Vincent
  • Mazelle Christian
  • Jacquey Christian
  • Aoustin Claude
  • Barthe Alain
  • Cadu Alexandre
  • Fedorov Andréi
  • Frezoul Anne-Marie
  • Garat Catherine
  • Le Comte Eric
  • Lee Qiu-Mei
  • Médale Jean-Louis
  • Moirin David
  • Penou Emmanuel
  • Petiot Mathieu
  • Peyre Guy
  • Rouzaud Jean
  • Séran Henry-Claude
  • Nĕmec̆ek Zdenĕk
  • S̆afránková Jana
  • Marcucci Maria Federica
  • Bruno Roberto
  • Consolini Giuseppe
  • Miyake Wataru
  • Shinohara Iku
  • Hasegawa Hiroshi
  • Seki Kanako
  • Coates Andrew
  • Leblanc Frédéric
  • Verdeil Christophe
  • Katra Bruno
  • Fontaine D.
  • Illiano Jean-Marie
  • Berthelier Jean-Jacques
  • Techer Jean-Denis
  • Fraenz Markus
  • Fischer Henning
  • Krupp Norbert
  • Woch Joachim
  • Bührke Ulrich
  • Fiethe Björn
  • Michalik Harald
  • Matsumoto Haruhisa
  • Yanagimachi Tomoki
  • Miyoshi Yoshizumi
  • Mitani Takefumi
  • Shimoyama Manabu
  • Zong Qiugang
  • Wurz Peter
  • Andersson Herman
  • Karlsson Stefan
  • Holmström Mats
  • Kazama Yoichi
  • Ip Wing-Huen
  • Hoshino Masahiro
  • Fujimoto Masaki
  • Terada Naoki
  • Keika Kunihiro
  • Dandouras Iannis
  Space Science Reviews, Springer Verlag, 2021, 217 (5), pp.70. BepiColombo Mio (previously called MMO: Mercury Magnetospheric Orbiter) was successfully launched by Ariane 5 from Kourou, French Guiana on October 20, 2018. The Mercury Plasma/Particle Experiment (MPPE) is a comprehensive instrument package onboard Mio spacecraft used for plasma, high-energy particle and energetic neutral atom measurements. It consists of seven sensors including two Mercury Electron Analyzers (MEA1 and MEA2), Mercury Ion Analyzer (MIA), Mass Spectrum Analyzer (MSA), High Energy Particle instrument for electron (HEP-ele), High Energy Particle instrument for ion (HEP-ion), and Energetic Neutrals Analyzer (ENA). Significant efforts were made pre-flight to calibrate all of the MPPE sensors at the appropriate facilities on the ground. High voltage commissioning of MPPE analyzers was successfully performed between June and August 2019 and in February 2020 following the completion of the low voltage commissioning in November 2018. Although all of the MPPE analyzers are now ready to begin observation, the full service performance has been delayed until Mio’s arrival at Mercury. Most of the fields of view (FOVs) of the MPPE analyzers are blocked by the thermal shield surrounding the Mio spacecraft during the cruising phase. Together with other instruments on Mio including Magnetic Field Investigation (MGF) and Plasma Wave Investigation (PWI) that measure plasma field parameters, MPPE will contribute to the comprehensive understanding of the plasma environment around Mercury when BepiColombo/Mio begins observation after arriving at the planet Mercury in December 2025. (10.1007/s11214-021-00839-2)
  DOI : 10.1007/s11214-021-00839-2
• Observations of Short‐Period Ion‐Scale Current Sheet Flapping
  
  • Richard L.
  • Khotyaintsev Yu.
  • Graham D.
  • Sitnov M.
  • Le Contel O.
  • Lindqvist P.‐a.
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2021, 126 (8). (10.1029/2021JA029152)
  DOI : 10.1029/2021JA029152
• Whistler instability driven by the sunward electron deficit in the solar wind
  
  • Berčič Laura
  • Verscharen Daniel
  • Owen Christopher J. J
  • Colomban Lucas
  • Kretzschmar Matthieu
  • Chust Thomas
  • Maksimović Milan
  • Kataria Dhiren
  • Anekallu C.
  • Behar Etienne
  • Berthomier Matthieu
  • Bruno Roberto
  • Fortunato Vito
  • Kelly Christopher W. W
  • Khotyaintsev Yuri. V. V
  • Lewis Gethyn R. R
  • Livi Stefano
  • Louarn Philippe
  • Mele Gennaro
  • Nicolaou Georgios
  • Watson Gillian
  • Wicks Robert T. T
  Astronomy & Astrophysics - A&A, EDP Sciences, 2021, 656 (A31), pp.10 pages. Solar wind electrons play an important role in the energy balance of the solar wind acceleration by carrying energy into interplanetary space in the form of electron heat flux. The heat flux is stored in the complex electron velocity distribution functions (VDFs) shaped by expansion, Coulomb collisions, and field-particle interactions. We investigate how the suprathermal electron deficit in the anti-strahl direction, which was recently discovered in the near-Sun solar wind, drives a kinetic instability and creates whistler waves with wave vectors that are quasi-parallel to the direction of the background magnetic field. We combine high-cadence measurements of electron pitch-angle distribution functions and electromagnetic waves provided by Solar Orbiter during its first orbit. Our case study is based on a burst-mode data interval from the Electrostatic Analyser System (SWA-EAS) at a distance of 112 $R_S$ (0.52 au) from the Sun, during which several whistler wave packets were detected by Solar Orbiter's Radio and Plasma Waves (RPW) instrument. The sunward deficit creates kinetic conditions under which the quasi-parallel whistler wave is driven unstable. We directly test our predictions for the existence of these waves through solar wind observations. We find whistler waves that are quasi-parallel and almost circularly polarised, propagating away from the Sun, coinciding with a pronounced sunward deficit in the electron VDF. The cyclotron-resonance condition is fulfilled for electrons moving in the direction opposite to the direction of wave propagation, with energies corresponding to those associated with the sunward deficit. (10.1051/0004-6361/202140970)
  DOI : 10.1051/0004-6361/202140970
• General Exact Law of Compressible Isentropic Magnetohydrodynamic Flows: Theory and Spacecraft Observations in the Solar Wind
  
  • Simon P.
  • Sahraoui F.
  The Astrophysical Journal, American Astronomical Society, 2021, 916 (1), pp.49. (10.3847/1538-4357/ac0337)
  DOI : 10.3847/1538-4357/ac0337
• Measurement of the two-photon excitation cross-section of the 6p′[3/2]2 and 6p′[1/2]0 levels of Xe I at the wavelengths 224.3 and 222.6 nm
  
  • Drag C
  • Marmuse F
  • Blondel Christophe
  Plasma Sources Science and Technology, IOP Publishing, 2021, 30 (7), pp.075026. The two-photon excitation cross-section is a key parameter for the two-photon absorption laser induced fluorescence (TALIF) method, which is commonly used to measure atomic densities in gaseous media, especially for plasma diagnostics. The method consists in recording the fluorescence signal that follows the resonant absorption of two photons of UV light. Calibration often relies on comparing the signal recorded in the studied sample with the fluorescence produced, at a similar wavelength, in a noble gas vapor, the density of which can be easily known. The ratio of the involved cross-sections however plays an essential role for the accuracy of such measurements. Yet the two-photon excitation cross-section of atomic xenon, which is often used as the reference for oxygen density measurements, was measured only once, at the wavelengths of interest. The aim of the present study has been to consolidate the experimental value of that key parameter. The cross-section is found equal to 1.36+0.46-0.34 and 1.88+0.75-0.54 10-43 m4 for the 6p'[3=2]2 and 6p'[1=2]0 levels, respectively. For the 6p'[3=2]2 level this is more than twice smaller than previously admitted. Even though the necessarily large relative uncertainty of a non-linear cross-section attaches a relatively large uncertainty to this factor of one half, the result suggests that atomic densities already measured by Xe-calibrated TALIF may have to be revised to significantly lower values. The experiments performed also provide an opportunity to revisit the validity of the approximations used for quantitative TALIF measurements and the collisional broadening and pressure shift of the two-photon 6p'[1=2]0 line. A new formula has been used to describe the two-photon absorption of a Gaussian beam in a long gas cell, which makes the decrease of the beam intensity a simple analytic expression even in strong absorption regime, based on a polylogarithmic function of the absorption rate variable. (10.1088/1361-6595/abfbeb)
  DOI : 10.1088/1361-6595/abfbeb
• The Sunward Electron Deficit: A Telltale Sign of the Sun’s Electric Potential
  
  • Halekas J.
  • Berčič Laura
  • Whittlesey P.
  • Larson D.
  • Livi R.
  • Berthomier Matthieu
  • Kasper J.
  • Case A.
  • Stevens M.
  • Bale S.
  • Macdowall R.
  • Pulupa M.
  The Astrophysical Journal, American Astronomical Society, 2021, 916 (1), pp.16. (10.3847/1538-4357/ac096e)
  DOI : 10.3847/1538-4357/ac096e
• Modélisation et simulation des plasmas de tokamak : états stationnaires axisymétriques à flot non nul
  
  • Oueslati Hanen
  , 2021. La détermination classique des équilibres des plasmas de tokamaks repose sur la résolution de l'équation de Grad-Shafranov. On y suppose que le plasma, vu comme un fluide conducteur, a une vitesse nulle. Expérimentale-ment, il existe de nombreuses observations d'une rotation spontanée dans les tokamaks notamment dans la direction toroïdale. Cette rotation du plasma s'avère avoir des effets très importants sur l'amélioration du confinement et le pas-sage dans le mode H de confinement amélioré. Pour éclaircir ces observations expérimentales, nous nous proposons de déterminer numérique-ment les états stationnaires axisymétriques des équations non-linéaires de la magnétohydrodynamique visco-résistive obtenues en réintroduisant le terme convectif. Cette étude doit prendre en compte le forçage dû à la présence d'un champ électrique extérieur dans la direction toroïdale servant à créer le courant toroïdal nécessaire dans un tokamak à la création de la composante poloïdale du champ magnétique. Nous présentons d'abord des résultats numériques obtenus dans les géométries de tokamak de type JET et ITER dans le cas d'une résistivité uniforme et sans perturbation magnétique. Nous avons considéré des valeurs réalistes de la résistivité et nous avons fait varier la viscosité, dont l'ordre de grandeur réaliste est mal connu. On définit un paramètre de contrôle appelé le nombre de Hartman H, nombre sans dimension qui implique à la fois la viscosité et la résistivité H=(ην)-1/2. Plus H augmente plus la vitesse dans la direction toroïdale augmente. De plus, toutes choses égales par ailleurs, la vitesse toroïdale caractéristique est une fonction croissante de la température du plasma et est plus grande en géométrie ITER que dans JET. On montre dans un deuxième temps l'effet d'une petite perturbation des configurations magnétiques sur la variation de la vitesse toroïdale. La symétrie est brisée pour de faibles perturbations axisymétriques. Par conséquent, la vitesse de rotation du plasma augmente. L'étude précédente considère une résistivité uniforme. On montre qu'un chauffage localisé, en introduisant une résistivité η(T)qui dépend de la température, conduit à une augmentation de la vitesse allant jusqu'à quatre ordres de grandeur de vitesses toroïdales par rapport à la situation avec une température uniforme pour des nombres de Hartmann identiques. Des résultats numériques pour plusieurs variations de température (∆T) sont présentés. Dans toutes ces simulations, le modèle MHD visco-résistif, détaillé dans le chapitre 3,est résolu à l'aide de la méthode des éléments finis en utilisant le code open source FreeFem++ de résolution numérique d'équations aux dérivées partielles.
• 2D radial-azimuthal particle-in-cell benchmark for E × B discharges
  
  • Villafana W
  • Petronio Federico
  • Denig A
  • Jimenez M
  • Eremin D
  • Garrigues Laurent
  • Taccogna F
  • Alvarez-Laguna Alejandro
  • Boeuf Jean-Pierre
  • Bourdon Anne
  • Chabert Pascal
  • Charoy Thomas
  • Cuenot B
  • Hara K
  • Pechereau F
  • Smolyakov A
  • Sydorenko D
  • Tavant A
  • Vermorel O
  Plasma Sources Science and Technology, IOP Publishing, 2021, 30 (7), pp.075002. In this paper we propose a representative simulation test-case of E × B discharges accounting for plasma wall interactions with the presence of both the electron cyclotron drift instability and the modified-two-stream-instability. Seven independently developed particle-in-cell (PIC) codes have simulated this benchmark case, with the same specified conditions. The characteristics of the different codes and computing times are given. Results show that both instabilities were captured in a similar fashion and good agreement between the different PIC codes is reported as main plasma parameters were closely related within a 5% interval. The number of macroparticles per cell was also varied and statistical convergence was reached. Detailed outputs are given in the supplementary data, to be used by other similar groups in the perspective of code verification (10.1088/1361-6595/ac0a4a)
  DOI : 10.1088/1361-6595/ac0a4a