Publications

2022

• SPIS Improvements of the Physical Modelling of the Electrostatic Cleanliness Concerning Scientific Missions with Active Potential Control
  
  • Sarrailh Pierre
  • Hess Sébastien L G
  • Villemant Marc
  • Retino A.
  • Tcherniatinsky Guillaume
  • Jeanty-Ruard Benjamin
  • Forest Julien
  • Cipriani Fabrice
  • Deprez Grégoire
  , 2022. The previous versions of SPIS [1], Spacecraft Plasma Interaction Software, was already used in a large amount of fields going from surface charging in GEO to simulation of electric propulsion or dusts transport. Inside this field of applications, the simulations of the electrostatic cleanliness of the scientific missions is a very important topic. It requires a continuous effort of modelling improvement in order to increase the predictability of the software in term in precision and in range of equipment taken into account. The MEEIES (Modelling of the Electrostatic Environment of Ion Emitting Spacecraft) project was performed under an ESA Technology Research Program. It consisted into the design, implementation and validation of new models in SPIS aiming to improve the physical modelling of the electrostatic cleanliness of an ion emitting spacecraft and the current performance of the software. This work has focused on the SPIS modelling limitations observed in performing a simulation of a scientific spacecraft in near-Earth’s plasma environment such as the Cluster mission. The limitations were observed into five different topics: the environment description, the active potential control (ASPOC) modelling, the electromagnetic coupling, the wire and end of booms approximations. In the frame of this paper, we will present the major improvements of SPIS. A realistic ASPOC device has been included with the possibility to emit neutral, ions and droplets from the surface elements. This development is combined with new electric circuit capabilities permitting to add complex behaviour (such like a sinusoidal generator or a pulse generator and bias circuit) and the capability to model improved scientific instruments (improved Langmuir probes and double-probe electric field instruments , advanced particle detectors, potential and current probes). These developments have permitted to improve the understanding of the electrostatic response and behaviour of the Spacecraft itself, as well as to simulate the active behaviour of the Cluster spacecraft and to compare the effects on particle detector and on antennae measurements with Cluster data during ASPOC operations. Concerning the environment, the capability to define time varying environment populations including external electric or magnetic field and electromagnetic waves has been implemented. It has been coupled with a low frequency electromagnetic solver (using a generalized Ohm's law for electron) able to capture the first order of ion related phenomena. In combination with the reworked thin wire approximation and including end of booms, it permits to model guarded probes at the end of the booms. These improvements will be also illustrated comparing low frequency electric field measured by Cluster with SPIS simulations. As a conclusion, we will show examples where simulations are now in excellent agreement with measurements from Cluster concerning particles and fields. We will also discuss about the areas that are still requiring some improvements and in particular the material properties used for the simulations. [1] S. L. G. Hess et al., “Improvement of the Spacecraft-Plasma Interaction Software (SPIS) with a new versatile architecture and enhanced modeling capabilities for electric propulsion,” 2018.
• A study of vTEC above Nepal exploring different calibration techniques, including a comparison with the NeQuick-2 model
  
  • Poudel P.
  • Silwal A.
  • Ghimire B D
  • Gautam S P
  • Karki M.
  • Chapagain N P
  • Adhikari B.
  • Pandit D.
  • Amory-Mazaudier C.
  Astrophysics and Space Science, Springer Verlag, 2022, 367 (4), pp.41. In this paper, we investigate the performance of the NeQuick 2 (NeQ-2) model with respect to Ciraolo's and Gopi's derived ionospheric vertical TEC (vTEC) during the years 2014 and 2015. GPS observables derived from dual-frequency receivers over western Nepal (Simikot, Bhimchula and Nepalganj) are processed to obtain the experimental vTEC utilizing Gopi's and Ciraolo's calibration procedures. The monthly and seasonal behavior of vTEC obtained from each calibration technique is compared with the vTEC obtained from the NeQ-2 model during a quiet period. It is observed that the vTEC value obtained from all studied approaches started to increase from 00:00 UT, reached a maximum around 08:00 UT, followed by declination, attaining a minimum value around 23:00 UT. Moreover, a comparative study showed that vTEC computed using the Ciraolo calibration technique overestimates GPS vTEC, calculated in all hours and months by Gopi's approach. In the spring and summer, vTEC derived using Ciraolo's TEC calibration overestimates NeQ-2 and underestimates it in the autumn and winter. Except for a few day hours in March and April 2014 (solar maximum), NeQ-2 prediction overestimated Gopi calibrated GPS vTEC. In daytime hours, a considerable difference is noted between one vTEC estimate with respect to another. NeQ-2 model vTEC is favourably associated with GPS vTEC obtained using the Gopi procedure in spring and correlates with the Ciraolo technique in autumn. Two GPS vTEC estimations demonstrate superior consistency in summer and winter 2 seasons over all studied stations. The study on geomagnetically disturbed conditions demonstrates that NeQ-2 is not responding to the storm influence. However, the mean absolute difference between NeQ-2 prediction and GPS vTEC procured through the Gopi approach is less on the storm event day. By contrast, it is discovered less by the Ciraolo technique when the storm is recovering (except for few cases). (10.1007/s10509-022-04041-w)
  DOI : 10.1007/s10509-022-04041-w
• Effects of ionospheric plasma irregularities at the equatorial zone on GPS signal
  
  • Ndao Amath
  • Gaye Idrissa
  • Fleury Rolland
  • Sarr Cheikh
  • Mazaudier Christine Amory
  Journal of scientific and Engineering Research, CODEN(USA) : JSERBR, 2022. This paper studies scintillations of the GPS signal in the equatorial zone created by the ionospheric plasma irregularities. RINEX Data resulting from GPS stations located at ±20° from the magnetic equator were used. This study was carried out by considering three GPS stations including the station from Dakar, that of Yamoussoukro and that of Cotonou. They belong to the IGS (International GNSS Services) network. The equatorial zone is one of most impacted areas by ionospheric irregularities causing scintillations of GPS signal which affect the phase measurement and thus can degrade the GPS receiver's performances during a positioning. The ROTI index was calculated to detect existing ionospheric irregularities. This index enabled us to detect scintillations of the GPS signal on a positioning situation. (10.5281/zenodo.10519162)
  DOI : 10.5281/zenodo.10519162
• Three-dimensional unsteady model of arc heater plasma flow
  
  • Meurisse Jeremie B.E.
  • Alvarez Laguna Alejandro
  • Panesi Marco
  • Mansour Nagi
  Aerospace Science and Technology, Elsevier, 2022, 123, pp.107465. (10.1016/j.ast.2022.107465)
  DOI : 10.1016/j.ast.2022.107465
• The Magnetopause: an almost tangential interface between the magnetosphere and the magnetosheath
  
  • Ballerini Giulio
  • Rezeau Laurence
  • Gérard Belmont
  • Francesco Califano
  , 2022.
• Ambipolar electrostatic field in dusty plasma
  
  • Hadid L. Z.
  • Shebanits O.
  • Wahlund J.-E.
  • Morooka M. W.
  • Nagy A.
  • Farrell W. M.
  • Holmberg M. K. G.
  • Modolo Ronan
  • Persoon A. M.
  • Tseng W. L.
  • Ye S.-Y.
  Journal of Plasma Physics, Cambridge University Press (CUP), 2022, 88 (2), pp.555880201. We study the effect of negatively charged dust on the magnetic-field-aligned polarisation electrostatic field (E) using Cassini's RPWS/LP in situ measurements during the 'ring-grazing' orbits. We derive a general expression for E and estimate for the first time in situ E (approximately 10 −5 V m −1) near the Janus and Epimetheus rings. We further demonstrate that the presence of the negatively charged dust close to the ring plane (|Z| 0.11 R s) amplifies E by at least one order of magnitude and reverses its direction due to the effect of the charged dust gravitational and inertial forces. Such reversal confines the electrons at the magnetic equator within the dusty region, around 0.047 R s above the ring plane. Furthermore, we discuss the role of the collision terms, in particular the ion-dust drag force, in amplifying E. These results imply that the charged dust, as small as nanometres in size, can have a significant influence on the plasma transport, in particular ambipolar diffusion along the magnetic field lines, and so their presence must be taken into account when studying such dynamical processes. (10.1017/s0022377822000186)
  DOI : 10.1017/s0022377822000186
• Energy Transfer, Discontinuities, and Heating in the Inner Heliosphere Measured with a Weak and Local Formulation of the Politano–Pouquet Law
  
  • David V.
  • Galtier S.
  • Sahraoui Fouad
  • Hadid L. Z.
  The Astrophysical Journal, American Astronomical Society, 2022, 927 (2), pp.200. Abstract The solar wind is a highly turbulent plasma for which the mean rate of energy transfer ε has been measured for a long time using the Politano–Pouquet (PP98) exact law. However, this law assumes statistical homogeneity that can be violated by the presence of discontinuities. Here, we introduce a new method based on the inertial dissipation  I σ whose analytical form is derived from incompressible magnetohydrodynamics; it can be considered as a weak and local (in space) formulation of the PP98 law whose expression is recovered after integration in space. We used  I σ to estimate the local energy transfer rate at scale σ from the THEMIS-B and Parker Solar Probe data taken in the solar wind at different heliospheric distances. Our study reveals that discontinuities near the Sun lead to a strong energy transfer that affects a wide range of scales σ . We also observe that switchbacks seem to be characterized by a singular behavior with an energy transfer varying as σ −3/4 , which slightly differs from classical discontinuities characterized by a σ −1 scaling. A comparison between the measurements of ε and  I σ shows that in general the latter is significantly larger than the former. (10.3847/1538-4357/ac524b)
  DOI : 10.3847/1538-4357/ac524b
• Progress from ASDEX Upgrade experiments in preparing the physics basis of ITER operation and DEMO scenario development
  
  • Stroth U.
  • Aguiam D.
  • Alessi E.
  • Angioni C.
  • Arden N.
  • Parra R. Arredondo
  • Artigues V.
  • Asunta O.
  • Balden M.
  • Bandaru V.
  • Banon-Navarro A.
  • Behler K.
  • Bergmann A.
  • Bergmann M.
  • Bernardo J.
  • Bernert M.
  • Biancalani A.
  • Bielajew R.
  • Bilato R.
  • Birkenmeier G.
  • Blanken T.
  • Bobkov V.
  • Bock A.
  • Body T.
  • Bolzonella T.
  • Bonanomi N.
  • Bortolon A.
  • Böswirth B.
  • Bottereau C.
  • Bottino A.
  • van den Brand H.
  • Brenzke M.
  • Brezinsek S.
  • Brida D.
  • Brochard F.
  • Bruhn C.
  • Buchanan J.
  • Buhler A.
  • Burckhart A.
  • Camenen Y.
  • Cannas B.
  • Megias P. Cano
  • Carlton D.
  • Carr M.
  • Carvalho P.
  • Castaldo C.
  • Cavedon M.
  • Cazzaniga C.
  • Challis C.
  • Chankin A.
  • Cianfarani C.
  • Clairet F.
  • Coda S.
  • Coelho R.
  • Coenen J.W.
  • Colas L.
  • Conway G.
  • Costea S.
  • Coster D.
  • Cote T.
  • Creely A.J.
  • Croci G.
  • Zabala D.J. Cruz
  • Cseh G.
  • Czarnecka A.
  • Cziegler I.
  • D’arcangelo O.
  • Molin A. Dal
  • David P.
  • Day C.
  • de Baar M.
  • de Marné P.
  • Delogu R.
  • Denk S.
  • Denner P.
  • Di Siena A.
  • Palacios Durán J.J. Dominguez
  • Dunai D.
  • Drenik A.
  • Dreval M.
  • Drube R.
  • Dunne M.
  • Duval B.P.
  • Dux R.
  • Eich T.
  • Elgeti S.
  • Encheva A.
  • Engelhardt K.
  • Erdös B.
  • Erofeev I.
  • Esposito B.
  • Fable E.
  • Faitsch M.
  • Fantz U.
  • Farnik M.
  • Faugel H.
  • Felici F.
  • Ficker O.
  • Fietz S.
  • Figueredo A.
  • Fischer R.
  • Ford O.
  • Frassinetti L.
  • Fröschle M.
  • Fuchert G.
  • Fuchs J.C.
  • Fünfgelder H.
  • Futatani S.
  • Galazka K.
  • Galdon-Quiroga J.
  • Escolà D. Gallart
  • Gallo A.
  • Gao Y.
  • Garavaglia S.
  • Muñoz M. Garcia
  • Geiger B.
  • Giannone L.
  • Gibson S.
  • Gil L.
  • Giovannozzi E.
  • Glöggler S.
  • Gobbin M.
  • Martin J. Gonzalez
  • Goodman T.
  • Gorini G.
  • Görler T.
  • Gradic D.
  • Granucci G.
  • Gräter A.
  • Greuner H.
  • Griener M.
  • Groth M.
  • Gude A.
  • Guimarais L.
  • Günter S.
  • Haas G.
  • Hakola A.H.
  • Ham C.
  • Happel T.
  • den Harder N.
  • Harrer G.
  • Harrison J.
  • Hauer V.
  • Hayward-Schneider T.
  • Heinemann B.
  • Hellsten T.
  • Henderson S.
  • Hennequin P.
  • Herrmann A.
  • Heyn E.
  • Hitzler F.
  • Hobirk J.
  • Höfler K.
  • Holm J.H.
  • Hölzl M.
  • Hopf C.
  • Horvath L.
  • Höschen T.
  • Houben A.
  • Hubbard A.
  • Huber A.
  • Hunger K.
  • Igochine V.
  • Iliasova M.
  • Ilkei T.
  • Björk K. Insulander
  • Ionita-Schrittwieser C.
  • Ivanova-Stanik I.
  • Jacob W.
  • Jaksic N.
  • Janky F.
  • Jansen van Vuuren A.
  • Jardin A.
  • Jaulmes F.
  • Jenko F.
  • Jensen T.
  • Joffrin E.
  • Kallenbach A.
  • Kálvin S.
  • Kantor M.
  • Kappatou A.
  • Kardaun O.
  • Karhunen J.
  • Käsemann C.-P.
  • Kasilov S.
  • Kendl A.
  • Kernbichler W.
  • Khilkevitch E.
  • Kirk A.
  • Hansen S. Kjer
  • Klevarova V.
  • Kocsis G.
  • Koleva M.
  • Komm M.
  • Kong M.
  • Krämer-Flecken A.
  • Krieger K.
  • Krivska A.
  • Kudlacek O.
  • Kurki-Suonio T.
  • Kurzan B.
  • Labit B.
  • Lackner K.
  • Laggner F.
  • Lahtinen A.
  • Lang P.T.
  • Lauber P.
  • Leuthold N.
  • Li L.
  • Likonen J.
  • Linder O.
  • Lipschultz B.
  • Liu Y.
  • Lohs A.
  • Lu Z.
  • Luda Di Cortemiglia T.
  • Luhmann N.C.
  • Lunt T.
  • Lyssoivan A.
  • Maceina T.
  • Madsen J.
  • Magnanimo A.
  • Maier H.
  • Mailloux J.
  • Maingi R.
  • Maj O.
  • Maljaars E.
  • Manas P.
  • Mancini A.
  • Manhard A.
  • Mantica P.
  • Mantsinen M.
  • Manz P.
  • Maraschek M.
  • Marchetto C.
  • Marrelli L.
  • Martin P.
  • Martitsch A.
  • Matos F.
  • Mayer M.
  • Mayoral M.-L.
  • Mazon D.
  • Mccarthy P.J.
  • Mcdermott R.
  • Merkel R.
  • Merle A.
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  • Meyer H.
  • Milanesio D.
  • Cabrera P. Molina
  • Monaco F.
  • Muraca M.
  • Nabais F.
  • Naulin V.
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  • Nem R.D.
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  • Neu G.
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  • Nielsen A.H.
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  • Pan O.
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  • Pau A.
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  • Ryter F.
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  • Schmitz O.
  • Schneider P.A.
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  • Shabbir A.
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  • Spizzo G.
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  • Lopez G. Suarez
  • Sun H.-J.
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  • Sytova E.
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  • Told D.
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  • Trevisan G.
  • Trier E.
  • Tripský M.
  • Usoltceva M.
  • Valisa M.
  • Valovic M.
  • van Zeeland M.
  • Vannini F.
  • Vanovac B.
  • Varela P.
  • Varoutis S.
  • Vianello N.
  • Vicente J.
  • Verdoolaege G.
  • Vierle T.
  • Viezzer E.
  • Voitsekhovitch I.
  • von Toussaint U.
  • Wagner D.
  • Wang X.
  • Weiland M.
  • White A.E.
  • Willensdorfer M.
  • Wiringer B.
  • Wischmeier M.
  • Wolf R.
  • Wolfrum E.
  • Yang Q.
  • Yu Q.
  • Zagórski R.
  • Zammuto I.
  • Zehetbauer T.
  • Zhang W.
  • Zholobenko W.
  • Zilker M.
  • Zito A.
  • Zohm H.
  • Zoletnik S.
  • Eurofusion Mst1 Team The
  Nuclear Fusion, IOP Publishing, 2022, 62 (4), pp.042006. Abstract An overview of recent results obtained at the tokamak ASDEX Upgrade (AUG) is given. A work flow for predictive profile modelling of AUG discharges was established which is able to reproduce experimental H-mode plasma profiles based on engineering parameters only. In the plasma center, theoretical predictions on plasma current redistribution by a dynamo effect were confirmed experimentally. For core transport, the stabilizing effect of fast ion distributions on turbulent transport is shown to be important to explain the core isotope effect and improves the description of hollow low- Z impurity profiles. The L–H power threshold of hydrogen plasmas is not affected by small helium admixtures and it increases continuously from the deuterium to the hydrogen level when the hydrogen concentration is raised from 0 to 100%. One focus of recent campaigns was the search for a fusion relevant integrated plasma scenario without large edge localised modes (ELMs). Results from six different ELM-free confinement regimes are compared with respect to reactor relevance: ELM suppression by magnetic perturbation coils could be attributed to toroidally asymmetric turbulent fluctuations in the vicinity of the separatrix. Stable improved confinement mode plasma phases with a detached inner divertor were obtained using a feedback control of the plasma β . The enhanced D α H-mode regime was extended to higher heating power by feedback controlled radiative cooling with argon. The quasi-coherent exhaust regime was developed into an integrated scenario at high heating power and energy confinement, with a detached divertor and without large ELMs. Small ELMs close to the separatrix lead to peeling-ballooning stability and quasi continuous power exhaust. Helium beam density fluctuation measurements confirm that transport close to the separatrix is important to achieve the different ELM-free regimes. Based on separatrix plasma parameters and interchange-drift-Alfvén turbulence, an analytic model was derived that reproduces the experimentally found important operational boundaries of the density limit and between L- and H-mode confinement. Feedback control for the X-point radiator (XPR) position was established as an important element for divertor detachment control. Stable and detached ELM-free phases with H-mode confinement quality were obtained when the XPR was moved 10 cm above the X-point. Investigations of the plasma in the future flexible snow-flake divertor of AUG by means of first SOLPS-ITER simulations with drifts activated predict beneficial detachment properties and the activation of an additional strike point by the drifts. (10.1088/1741-4326/ac207f)
  DOI : 10.1088/1741-4326/ac207f
• Editorial: The Role of Turbulence in the Solar Wind, Magnetosphere, Ionosphere Dynamics
  
  • Stepanova Marina
  • Borovsky Joseph
  • Retino Alessandro
  • Uritsky Vadim
  • Vörös Zoltán
  • Zimbardo Gaetano
  Frontiers in Astronomy and Space Sciences, Frontiers Media, 2022, 8. (10.3389/fspas.2021.763190)
  DOI : 10.3389/fspas.2021.763190
• The angular pattern in the hyperfine structure of Xe I and Kr I atoms
  
  • Blondel Christophe
  • Drag Cyril
  Journal of Physics B: Atomic, Molecular and Optical Physics, IOP Publishing, 2022, 55 (1), pp.015001. Recent reviews of the hyperfine structure of xenon and krypton have highlighted the variety of the values taken by the hyperfine coefficients A and B of these atoms. These variations, as functions of the atomic angular momenta, were however not explained quantitatively. This article shows the simple picture and angular momentum algebra that make it possible to account for the observed trend. The only necessary approximations are to consider the interaction of the outer electron negligible with respect to the coupling of the p5 core with the nucleus, and to assume that the Racah |(p5)j,l[K]J,F> basis, conventionally used for the atomic states of noble gases, makes a fitting description of the hierarchy of their angular momentum couplings. The way the calculation corroborates the apparently erratic values of hyperfine coefficients A and B in Xe I and Kr I shows up as a confirmation of the validity of these approximations. (10.1088/1361-6455/ac3f98)
  DOI : 10.1088/1361-6455/ac3f98
• Operating a full tungsten actively cooled tokamak: overview of WEST first phase of operation
  
  • Bucalossi J.
  • Achard J.
  • Agullo O.
  • Alarcon T.
  • Allegretti L.
  • Ancher H.
  • Antar G.
  • Antusch S.
  • Anzallo V.
  • Arnas C.
  • Arranger D.
  • Artaud J.F.
  • Aumeunier M.H.
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  • Bai X.
  • Balbin J.
  • Balorin C.
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  • Barbuti A.
  • Barlerin J.
  • Basiuk V.
  • Batal T.
  • Baulaigue O.
  • Bec A.
  • Bécoulet M.
  • Benoit E.
  • Benard E.
  • Benard J.M.
  • Bertelli N.
  • Bertrand E.
  • Beyer P.
  • Bielecki J.
  • Bienvenu P.
  • Bisson R.
  • Bobkov V.
  • Bodner G.
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  • Bourg J.
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  • Brochard F.
  • Brun C.
  • Bruno V.
  • Bufferand H.
  • Bureau A.
  • Burles S.
  • Camenen Y.
  • Cantone B.
  • Caprin E.
  • Carpentier S.
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  • Chanet N.
  • Chellai O.
  • Chen Y.
  • Chernyshova M.
  • Chmielewski P.
  • Choe W.
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  • Ciraolo G.
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  • Coenen J.
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  • Corbel E.
  • Corre Y.
  • Costea S.
  • Courtois X.
  • Czarski T.
  • Daniel R.
  • Daumas J.
  • de Combarieu M.
  • de Temmerman G.
  • de Vries P.
  • Dechelle C.
  • Deguara F.
  • Dejarnac R.
  • Delaplanche J.M.
  • Delgado-Aparicio L.F.
  • Delmas E.
  • Delpech L.
  • Desgranges C.
  • Devynck P.
  • Di Genova S.
  • Diab R.
  • Diallo A.
  • Diez M.
  • Dif-Pradalier G.
  • Dimitrova M.
  • Ding B.
  • Dittmar T.
  • Doceul L.
  • Domenes M.
  • Douai D.
  • Dougnac H.
  • Duan X.
  • Dubus L.
  • Dumas N.
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  • Serre E.
  • Shin H.
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  • Signoret Ja.
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  • Simonin A.
  • Skalli Fettachi O.
  • Song Y.
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  • van Eester D.
  • van Rooij G.
  • Vartanian S.
  • Verger J.M.
  • Vermare L.
  • Vézinet D.
  • Vignal N.
  • Vincent B.
  • Vives S.
  • Volpe D.
  • Wallace G.
  • Wang E.
  • Wang L.
  • Wang Yi.
  • Wang Yo.
  • Wauters T.
  • Wirth B.
  • Wirtz M.
  • Wojenski A.
  • Wright J.
  • Xu M.
  • Yang Q.
  • Yang H.
  • Zago B.
  • Zhang B.
  • Zhang X.
  • Zou X.
  Nuclear Fusion, IOP Publishing, 2022, 62 (4), pp.042007. Abstract WEST is an MA class superconducting, actively cooled, full tungsten (W) tokamak, designed to operate in long pulses up to 1000 s. In support of ITER operation and DEMO conceptual activities, key missions of WEST are: (i) qualification of high heat flux plasma-facing components in integrating both technological and physics aspects in relevant heat and particle exhaust conditions, particularly for the tungsten monoblocks foreseen in ITER divertor; (ii) integrated steady-state operation at high confinement, with a focus on power exhaust issues. During the phase 1 of operation (2017–2020), a set of actively cooled ITER-grade plasma facing unit prototypes was integrated into the inertially cooled W coated startup lower divertor. Up to 8.8 MW of RF power has been coupled to the plasma and divertor heat flux of up to 6 MW m −2 were reached. Long pulse operation was started, using the upper actively cooled divertor, with a discharge of about 1 min achieved. This paper gives an overview of the results achieved in phase 1. Perspectives for phase 2, operating with the full capability of the device with the complete ITER-grade actively cooled lower divertor, are also described. (10.1088/1741-4326/ac2525)
  DOI : 10.1088/1741-4326/ac2525
• Formation of the radial electric field profile in the WEST tokamak
  
  • Vermare L.
  • Hennequin P.
  • Honoré C.
  • Peret M.
  • Dif-Pradalier Guilhem
  • Garbet X.
  • Gunn J.
  • Bourdelle C.
  • Clairet F.
  • Varennes R.
  • Morales J.
  • Dumont R.
  • Goniche M.
  • Maget P.
  Nuclear Fusion, IOP Publishing, 2022, 62 (2), pp.026002. (10.1088/1741-4326/ac3c85)
  DOI : 10.1088/1741-4326/ac3c85
• Signatures of Equatorial Plasma Bubbles and Ionospheric Scintillations from Magnetometer and GNSS Observations in the Indian Longitudes during the Space Weather Events of Early September 2017
  
  • Vankadara Ram Kumar
  • Panda Sampad Kumar
  • Amory-Mazaudier Christine
  • Fleury Rolland
  • Devanaboyina Venkata Ratnam
  • Pant Tarun Kumar
  • Jamjareegulgarn Punyawi
  • Haq Mohd Anul
  • Okoh Daniel
  • Seemala Gopi Krishna
  Remote Sensing, MDPI, 2022, 14 (3), pp.652. Scintillation due to ionospheric plasma irregularities remains a challenging task for the space science community as it can severely threaten the dynamic systems relying on space-based navigation services. In the present paper, we probe the ionospheric current and plasma irregularity characteristics from a latitudinal arrangement of magnetometers and Global Navigation Satellite System (GNSS) stations from the equator to the far low latitude location over the Indian longitudes, during the severe space weather events of 6–10 September 2017 that are associated with the strongest and consecutive solar flares in the 24th solar cycle. The night-time influence of partial ring current signatures in ASYH and the daytime influence of the disturbances in the ionospheric E region electric currents (Diono) are highlighted during the event. The total electron content (TEC) from the latitudinal GNSS observables indicate a perturbed equatorial ionization anomaly (EIA) condition on 7 September, due to a sequence of M-class solar flares and associated prompt penetration electric fields (PPEFs), whereas the suppressed EIA on 8 September with an inverted equatorial electrojet (EEJ) suggests the driving disturbance dynamo electric current (Ddyn) corresponding to disturbance dynamo electric fields (DDEFs) penetration in the E region and additional contributions from the plausible storm-time compositional changes (O/N2) in the F-region. The concurrent analysis of the Diono and EEJ strengths help in identifying the pre-reversal effect (PRE) condition to seed the development of equatorial plasma bubbles (EPBs) during the local evening sector on the storm day. The severity of ionospheric irregularities at different latitudes is revealed from the occurrence rate of the rate of change of TEC index (ROTI) variations. Further, the investigations of the hourly maximum absolute error (MAE) and root mean square error (RMSE) of ROTI from the reference quiet days’ levels and the timestamps of ROTI peak magnitudes substantiate the severity, latitudinal time lag in the peak of irregularity, and poleward expansion of EPBs and associated scintillations. The key findings from this study strengthen the understanding of evolution and the drifting characteristics of plasma irregularities over the Indian low latitudes. (10.3390/rs14030652)
  DOI : 10.3390/rs14030652
• Pushing the physics of edge transport barriers towards the wall : how do boundary conditions impact confinement transitions in tokamaks?
  
  • Peret Mathieu
  , 2022. This work deals with the understanding of transport barrier establishment in the edge of magnetically confined fusion plasmas. To that end, two main axis were explored. First, an experimental characterisation of the rotation profiles by Doppler Back-Scattering reflectometry (DBS) have been performed in the WEST tokamak. On the other hand, a theoretical development of transport models implying a spectral description of the turbulence and its interplay with sheared flows have been developed. In fact, tokamak plasmas can be decomposed in three regions of interest : a confined core region where the fusion reactions take place, a plasma-wall interaction region where the plasma intercepts the wall leading to power and particle exhaust and a transition region between the two firsts called edge region. The establishment of a transport barrier in this latter is attributed to the generation of a strongly sheared flow leading to a mitigation of the turbulence. Experimentally, the build up of the barrier appeared very sensitive to edge plasma conditions such as the magnetic configuration, i.e. the existence and the position of an X-point (where the poloidal magnetic field is null) as well as edge density amplitude.An experimental characterisation of edge rotation profiles has been managed in various plasma conditions showing impacts of heating power injection, magnetic geometry and density on both profiles amplitude and shape. In particular, the magnetic topology of the plasma appeared strongly influencing the rotation behaviour. The X-point position, i. e. symmetrically in the top or the bottom part of the plasma corresponding to the so-called unfavourable and favourable configurations, induces the presence or the absence of rotation well at the confined plasma boundary. This discrepancy becomes blurred when the plasma current increases. Moreover, the first observations of an increased confinement regime in the WEST tokamak show edge velocity records. Interestingly, a deeper well in the rotation profile is observed in unfavourable configuration even if the density profile exhibits a sightly weaker gradient at the edge (or a weaker pedestal).Aiming at understanding these features, a theoretical development has been derived to describe both transport and sheared flow/turbulence interplay. A spectral approach of the edge turbulent equations led to a description of all the features of the interchange turbulence plunged into a background sheared flow. From this starting point, a reconstruction of the principal transport observables such as fluctuation levels, fluxes or flow generation through the Reynolds stress creation is driven. Applied to the plasma-wall interaction region, this model gives predictions for particle exhaust characteristic width. Interestingly, the model remains simple enough to include more complex geometric and collisional effects. Indeed, this turbulence description only depends on three control parameters : the curvature drive depending on the geometry, the parallel dynamics features depending on both geometry and density conditions and the structure tilt due to magnetic and background flow shear. These effects are investigated and discussed regarding the impacts of plasma shaping and edge density on these control parameters. Then, this model has been verified against a broad set of 2D flux-driven simulations with control parameters in the range of the experimental ones. Furthermore, a comparison of the model predictions with experimental data revealed three validation steps. First, the model recovers turbulent spectra measured in the TJ-K torsatron. Then, comparing the predictions with turbulent features and background density profile decay lengths measured with Langmuir probes in Tore Supra results in a sound quantitative agreement. Finally, the model of flow generation by the turbulence recovers the experimental observations mentioned above concerning the impact of the magnetic geometry and the plasma current.
• Investigation of the homogeneity of energy conversion processes at dipolarization fronts from MMS measurements
  
  • Alqeeq S. W.
  • Le Contel O.
  • Canu Patrick
  • Retinò Alessandro
  • Chust Thomas
  • Mirioni Laurent
  • Richard L.
  • Aït-Si-Ahmed Y.
  • Alexandrova A.
  • Chuvatin A.
  • Ahmadi N.
  • Baraka S. M.
  • Nakamura R.
  • Wilder F. D.
  • Gershman D. J.
  • Lindqvist P. A.
  • Khotyaintsev Yu. V.
  • Ergun R. E.
  • Burch J. L.
  • Torbert R. B.
  • Russell C. T.
  • Magnes W.
  • Strangeway R. J.
  • Bromund K. R.
  • Wei H.
  • Plaschke F.
  • Anderson B. J.
  • Giles B. L.
  • Fuselier S. A.
  • Saito Y.
  • Lavraud B.
  Physics of Plasmas, American Institute of Physics, 2022, 29 (1), pp.012906. We report on six dipolarization fronts (DFs) embedded in fast earthward flows detected by the Magnetospheric Multiscale mission during a substorm event on 23 July 2017. We analyzed Ohm’s law for each event and found that ions are mostly decoupled from the magnetic field by Hall fields. However, the electron pressure gradient term is also contributing to the ion decoupling and likely responsible for an electron decoupling at DF. We also analyzed the energy conversion process and found that the energy in the spacecraft frame is transferred from the electromagnetic field to the plasma (J E > 0) ahead or at the DF, whereas it is the opposite (J E < 0) behind the front. This reversal is mainly due to a local reversal of the cross-tail current indicating a substructure of the DF. In the fluid frame, we found that the energy is mostly transferred from the plasma to the electromagnetic field (J E0 < 0) and should contribute to the deceleration of the fast flow. However, we show that the energy conversion process is not homogeneous at the electron scales due to electric field fluctuations likely related to lower-hybrid drift waves. Our results suggest that the role of DF in the global energy cycle of the magnetosphere still deserves more investigation. In particular, statistical studies on DF are required to be carried out with caution due to these electron scale substructures. (10.1063/5.0069432)
  DOI : 10.1063/5.0069432
• AVIP: a low temperature plasma code
  
  • Cheng Lionel
  • Barleon Nicolas
  • Vermorel Olivier
  • Cuenot Benedicte
  • Bourdon Anne
  , 2022. A new unstructured, massively parallel code dedicated to low temperature plasmas, AVIP, is presented to simulate plasma discharges in interaction with combustion. The plasma species are modeled in a drift-diffusion formulation and the Poisson equation is solved consistently with the charged species. Plasma discharges introduce stiff source terms on the reactive Navier-Stokes equations and Riemann solvers, more robust than the schemes available in AVBP, have been implemented in AVIP and reported back in AVBP to solve the reactive Navier-Stokes equations. The validation of all the numerical schemes is carried out in this paper where numerous validation cases are presented for the plasma drift-diffusions equations and the reactive Navier-Stokes equations.
• Quantification of surface charging memory effect in ionization wave dynamics
  
  • Viegas Pedro
  • Slikboer Elmar
  • Bonaventura Zdenek
  • Garcia-Caurel Enric
  • Guaitella Olivier
  • Sobota Ana
  • Bourdon Anne
  Scientific Reports, Nature Publishing Group, 2022, 12 (1), pp.1181. The dynamics of ionization waves (IWs) in atmospheric pressure discharges is fundamentally determined by the electric polarity (positive or negative) at which they are generated and by the presence of memory effects, i.e. leftover charges and reactive species that influence subsequent IWs. This work examines and compares positive and negative IWs in pulsed plasma jets (1 [Formula: see text]s on-time), showing the difference in their nature and the different resulting interaction with a dielectric BSO target. For the first time, it is shown that a surface charging memory effect is produced, i.e. that a significant amount of surface charges and electric field remain in the target in between discharge pulses (200 [Formula: see text]s off-time). This memory effect directly impacts IW dynamics and is especially important when using negative electric polarity. The results suggest that the remainder of surface charges is due to the lack of charged particles in the plasma near the target, which avoids a full neutralization of the target. This demonstration and the quantification of the memory effect are possible for the first time by using an unique approach, assessing the electric field inside a dielectric material through the combination of an advanced experimental technique called Mueller polarimetry and state-of-the-art numerical simulations. (10.1038/s41598-022-04914-8)
  DOI : 10.1038/s41598-022-04914-8
• Towards plasma jet controlled charging of a dielectric target at grounded, biased, and floating potential
  
  • Slikboer Elmar
  • Guaitella Olivier
  • Garcia-Caurel Enrique
  • Sobota Ana
  Scientific Reports, Nature Publishing Group, 2022, 12 (1), pp.1157. Electric field and surface charge measurements are presented to understand the dynamics in the plasma-surface interaction of a plasma jet and a dielectric surface. The ITO coated backside of the dielectric allowed to impose a DC bias and thus compare the influence of a grounded, biased and floating potential. When imposing a controlled potential at the back of the target, the periodical charging is directly dependent on the pulse length, irrespective of that control potential. This is because the plasma plume is sustained throughout the pulse. When uncontrolled and thus with a floating potential surface, charge accumulation and potential build-up prevents a sustained plasma plume. An imposed DC bias also leads to a continuous surface charge to be present accumulated on the plasma side to counteract the bias. This can lead to much higher electric fields (55 kV/cm) and surface charge (200 nC/cm 2) than observed previously. When the plasma jet is turned off, the continuous surface charge decreased to half its value in 25 ms. These results have implications for surface treatment applications. (10.1038/s41598-022-05075-4)
  DOI : 10.1038/s41598-022-05075-4
• Effect of the electric field profile on the accuracy of E-FISH measurements in ionization waves
  
  • Chng Tat Loon
  • Pai David Z.
  • Guaitella Olivier
  • Starikovskaia Svetlana
  • Bourdon Anne
  Plasma Sources Science and Technology, IOP Publishing, 2022, 31 (1), pp.015010. Abstract Electric field induced second harmonic (E-FISH) generation has emerged as a versatile tool for measuring absolute electric field strengths in time-varying, non-equilibrium plasmas and gas discharges. Yet recent work has demonstrated that the E-FISH signal, when produced with tightly focused laser beams, exhibits a strong dependence on both the length and shape of the applied electric field profile (along the axis of laser beam propagation). In this paper, we examine the effect of this dependence more meaningfully, by predicting what an E-FISH experiment would measure in a plasma, using 2D axisymmetric numerical fluid simulations as the true value. A pin-plane nanosecond discharge at atmospheric pressure is adopted as the test configuration, and the electric field evolution during the propagation of the ionization wave (IW) is specifically analysed. We find that the various phases of this evolution (before and up to the front arrival, immediately behind the front and after the connection to the grounded plane) are quite accurately described by three unique electric field profile shapes, each of which produces a different response in the E-FISH signal. As a result, the accuracy of an E-FISH measurement is generally predicted to be comparable in the first and third phases of the IW evolution, and significantly poorer in the second (intermediate) phase. Fortunately, even though the absolute error in the field strength at certain time instants could be large, the overall shape of the field evolution curve is relatively well captured by E-FISH. Guided by the simulation results, we propose a procedure for estimating the error in the initial phase of the IW development, based on the presumption that the starting field profile mirrors that of its corresponding Laplacian conditions before evolving further. We expect that this approach may be readily generalized and applicable to other IW problems or phenomena, thus extending the utility of the E-FISH diagnostic. (10.1088/1361-6595/ac4592)
  DOI : 10.1088/1361-6595/ac4592
• Fundamental Electromagnetic Emissions by a Weak Electron Beam in Solar Wind Plasmas with Density Fluctuations
  
  • Krafft C.
  • Savoini P.
  The Astrophysical Journal Letters, Bristol : IOP Publishing, 2022, 924 (2), pp.L24. The generation of Langmuir wave turbulence by a weak electron beam in a randomly inhomogeneous plasma and its subsequent electromagnetic radiation are studied owing to two-dimensional particle-in-cell simulations in conditions relevant to type III solar radio bursts. The essential impact of random density fluctuations of average levels of a few percents of the background plasma on the characteristics of the electromagnetic radiation at the fundamental plasma frequency ω p is shown. Not only wave nonlinear interactions but also processes of Langmuir waves' transformations on the density fluctuations contribute to the generation of such emissions. During the beam relaxation, the amount of electromagnetic energy radiated at ω p in a plasma with density fluctuations strongly exceeds that observed when the plasma is homogeneous. The fraction of Langmuir wave energy involved in the generation of electromagnetic emissions at ω p saturates around 10 −4 , i.e., one order of magnitude above that reached when the plasma is uniform. Moreover, whereas harmonic emission at 2ω p dominates over fundamental emission during the time evolution in a homogeneous plasma, fundamental emission is strongly dominant when the plasma contains density fluctuations, at least during several thousands of plasma periods before being overcome by harmonic emission when the total electromagnetic energy begins to saturate. (10.3847/2041-8213/ac46a7)
  DOI : 10.3847/2041-8213/ac46a7
• Analysis of small scale fluctuations in Hall effect thrusters using virtual Thomson scattering on PIC simulations
  
  • Ben Slimane Tarek
  • Honoré Cyrille
  • Charoy Thomas
  • Bourdon Anne
  • Chabert Pascal
  Physics of Plasmas, American Institute of Physics, 2022, 29. Hall effect thrusters are yet not fully understood due to multiple open questions, among which the anomalous electron transport is the most challenging. Particle-In-Cell (PIC) simulations suggested that electron transport is strongly affected by small-scale instabilities which can be investigated experimentally using Collective Thomson Scattering (CTS). In this paper, we perform a virtual CTS diagnostic on PIC data in order to investigate these small scales and to relate simulation and experiments. The virtual diagnostic is performed on the electron density maps from a simplified 2D axial-azimuthal PIC simulation. Analysis along the channel axis showed two dominant modes at 8 rad.mm −1 and 3 rad.mm −1. These modes exhibit ion-acoustic wave features and appear to be selectively affected by the acceleration of the ions when transitioning from the ionization zone to the acceleration zone. A numerical study of the electron density fluctuation rate from the virtual CTS is also performed and the obtained profiles are compared to PIC. This reveals that the virtual CTS integrates both axial and azimuthal fluctuations of the electron density due to the spatial extension of the scattering volume. Moreover, it also highlights the importance of a good estimation of the electron density in the scattering volume for an accurate estimation of the fluctuation rate. (10.1063/5.0073215)
  DOI : 10.1063/5.0073215
• Use of Twenty Years CLUSTER/FGM Data to Observe the Mean Behavior of the Magnetic Field and Current Density of Earth's Magnetosphere
  
  • Robert P.
  • Dunlop M.
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2022, 127 (1). Abstract The data from the CLUSTER FGM magnetometer, recorded for 20 years at ESA's Cluster Science Archive, as well as the position of the spacecraft, have been used to form a database aligned in time. It allows the calculation of curl(B) over all the lifetime of the mission (representing the current density via ). The and data are then bin averaged, as a function of the dipole tilt angle, to form a 3D grid of spatial extent of about 20 RE, and for any spatial resolution. From these data grids, maps of the direction of the magnetic field and of the current density can be produced, allowing the observation of the average behavior of the magnetic field and the current density on a large scale. The validity of the calculation of is discussed. By means of spatial interpolation, the grids are used to provide a measurement of the magnetic field at any point in space where the grid is filled. This allows the possibility of ray tracing to obtain empirical plots of the magnetic field lines, that is, modeled from experimental data. Field lines near the cusp can be visualized, although smoothed by the averaging of the IMF and solar wind parameters. In future work it would be possible to add other classification criteria than just the dipole tilt angle, such as various activity indices and solar wind parameters. The prospect of adding data from other missions (such as MMS?) would extend the regions that have been covered by Cluster, and increase the spatial extent of the 3D grid and its resolution. (10.1029/2021JA029837)
  DOI : 10.1029/2021JA029837
• A Study of Solar Flare Effects on the Geomagnetic Field Components during Solar Cycles 23 and 24
  
  • Grodji Oswald Didier Franck
  • Doumbia Vafi
  • Amaechi Paul Obiakara
  • Diaby Kassamba Abdel Aziz
  • Amaechi Paul Obiakara
  • Amory-Mazaudier Christine
  • N’guessan Kouassi
  • Diaby Kassamba Abdel Aziz
  • Zie Tuo
  • Boka Kouadio
  Atmosphere, MDPI, 2022, 13 (1), pp.69. In this paper, we investigated the impact of solar flares on the horizontal (H), eastward (Y) and vertical (Z) components of the geomagnetic field during solar cycles 23 and 24 (SC23/24) using data of magnetometer measurements on the sunlit side of the Earth. We examined the relation between sunspot number and solar flare occurrence of various classes during both cycles. During SC23/24, we obtained correlation coefficient of 0.93/0.97, 0.96/0.96 and 0.60/0.56 for C-class, M-class and X-class flare, respectively. The three components of the geomagnetic field reached a peak a few minutes after the solar flare occurrence. Generally, the magnetic crochet of the H component was negative between the mid-latitudes and Low-latitudes in both hemispheres and positive at low latitudes. By contrast, the analysis of the latitudinal variation of the Y and Z components showed that unlike the H component, their patterns of variations were not coherent in latitude. The peak amplitude of solar flare effect (sfe) on the various geomagnetic components depended on many factors including the local time at the observing station, the solar zenith angle, the position of the station with respect to the magnetic equator, the position of solar flare on the sun and the intensity of the flare. Thus, these peaks were stronger for the stations around the magnetic equator and very low when the geomagnetic field components were close to their nighttime values. Both cycles presented similar monthly variations with the highest sfe value (ΔHsfe = 48.82 nT for cycle 23 and ΔHsfe = 24.68 nT for cycle 24) registered in September and lowest in June for cycle 23 (ΔHsfe = 8.69 nT) and July for cycle 24 (ΔHsfe = 10.69 nT). Furthermore, the sfe was generally higher in cycle 23 than in cycle 24. (10.3390/atmos13010069)
  DOI : 10.3390/atmos13010069
• Transport barrier in 5D gyrokinetic flux-driven simulations
  
  • Lo-Cascio G.
  • Gravier Etienne
  • Réveillé T.
  • Lesur M.
  • Sarazin Y.
  • Garbet X.
  • Vermare L.
  • Lim K.
  • Guillevic A.
  • Grandgirard V.
  Nuclear Fusion, IOP Publishing, 2022, 62 (12), pp.126026. Abstract Two ways for producing a transport barrier through strong shear of the E × B poloidal flow have been investigated using GYSELA gyrokinetic simulations in a flux-driven regime. The first one uses an external poloidal momentum (i.e. vorticity) source that locally polarizes the plasma, and the second one enforces a locally steep density profile that also stabilizes the ion temperature gradient (ITG) instability modes linearly. Both cases show a very low local turbulent heat diffusivity coefficient χ T turb and a slight increase in core pressure when a threshold of ω E × B ≈ γ ¯ lin (respectively the E × B shear rate and average linear growth rate of ITG) is reached, validating previous numerical results. This pressure increase and χ T turb quench are the signs of a transport barrier formation. This behaviour is the result of a reduced turbulence intensity which strongly correlates with the shearing of turbulent structures as evidenced by a reduction of the auto-correlation length of potential fluctuations as well as an intensity reduction of the k θ spectrum. Moreover, a small shift towards smaller poloidal wavenumber is observed in the vorticity source region which could be linked to a tilt of the turbulent structures in the poloidal direction. (10.1088/1741-4326/ac945d)
  DOI : 10.1088/1741-4326/ac945d
• Cyto- and bio-compatibility assessment of plasma-treated polyvinylidene fluoride scaffolds for cardiac tissue engineering
  
  • Kitsara Maria
  • Revet Gaëlle
  • Vartanian-Grimaldi Jean-Sébastien
  • Simon Alexandre
  • Minguy Mathilde
  • Miche Antoine
  • Humblot Vincent
  • Dufour Thierry
  • Agbulut Onnik
  Frontiers in Bioengineering and Biotechnology, Frontiers, 2022, 10, pp.1008436. As part of applications dealing with cardiovascular tissue engineering, drop-cast polyvinylidene fluoride (PVDF) scaffolds have been treated by cold plasma to enhance their adherence to cardiac cells. The scaffolds were treated in a dielectric barrier device where cold plasma was generated in a gaseous environment combining a carrier gas (helium or argon) with/without a reactive gas (molecular nitrogen). We show that an Ar-N2 plasma treatment of 10 min results in significant hydrophilization of the scaffolds, with contact angles as low as 52.4° instead of 132.2° for native PVDF scaffolds. Correlation between optical emission spectroscopy and X-ray photoelectron spectroscopy shows that OH radicals from the plasma phase can functionalize the surface scaffolds, resulting in improved wettability. For all plasma-treated PVDF scaffolds, the adhesion and maturation of primary cardiomyocytes is increased, showing a well-organized sarcomeric structure (α-actinin immunostaining). The efficacy of plasma treatment was also supported by real-time PCR analysis to demonstrate an increased expression of the genes related to adhesion and cardiomyocyte function. Finally, the biocompatibility of the PVDF scaffolds was studied in a cardiac environment, after implantation of acellular scaffolds on the surface of the heart of healthy mice. Seven and 28 days after implantation, no exuberant fibrosis and no multinucleated giant cells were visible in the grafted area, hence demonstrating the absence of foreign body reaction and the biocompatibility of these scaffolds. (10.3389/fbioe.2022.1008436)
  DOI : 10.3389/fbioe.2022.1008436