Publications

2021

• Towards a maintainable and high efficiency neutral beam system for future fusion reactors
  
  • Simonin A.
  • Blondel C.
  • Chaibi W.
  • Dechelle C.
  • Drag C.
  • Villedieu E.
  Nuclear Fusion, IOP Publishing, 2021, 61 (4), pp.046003. Achievement of an economic fusion reactor imposes a high level of unprecedented requirements for the Neutral Beam (NB) systems; the first one is the nuclear safety constraints which imposes prerequisite on the ease of access of all injector components to provide a preventive (and curative) maintenance by remote handling while maintaining reactor operation. In addition, the challenge is to develop high power injectors with very high wall-plug efficiency (above 60 %) able to operate in stable conditions over several months. There is a significant gap to bridge with respect to the present NB systems, which are handicapped by a low efficiency and by complex and long maintenance operations. Evidence that this injector concept does not offer adaptations to cope with the reactor requirements makes it clear that a new concept has to be addressed. An injector concept with modular sources at ground voltage is proposed. The concept makes remote maintenance of the injector components easier where each source module can be replaced by a new one without breaking the vacuum and affecting injector conditioning. With the grounded and modular ion source, photoneutralization associated with energy recovery appears as the best route capable of attaining the reactor requirements. This concept of maintainable NB system would provide a high heating power with a wall-plug efficiency above 70% and unprecedented features such as the capacity of producing temporal and spatial modulation of the beam power for a better control of the plasma stability. Up to now, photoneutralization feasibility studies already carried out on reduced-scale prototypes have not highlighted any showstoppers. Continuation of R&D in the years to come can pave the way towards the achievement of a first full-scale high power cavity in the 1 MW range, and to the realization of a multi-amperes (~10 A) thin blade-like D-beam. (10.1088/1741-4326/abdac2)
  DOI : 10.1088/1741-4326/abdac2
• Adsorption of VOCs Is a Key Step in Plasma-Catalyst Coupling: The Case of Acetone onto TiO2 vs. CeO2
  
  • Wang Xianjie
  • Barakat Christelle
  • Jia Zixian
  • Romanias Manolis
  • Thevenet Frederic
  • Rousseau Antoine
  Catalysts, MDPI, 2021, 11 (3), pp.350. (10.3390/catal11030350)
  DOI : 10.3390/catal11030350
• Correction to: SERENA: Particle Instrument Suite for Determining the Sun-Mercury Interaction from BepiColombo
  
  • Orsini S.
  • Livi S.
  • Lichtenegger H.
  • Barabash S.
  • Milillo A.
  • de Angelis E.
  • Phillips M.
  • Laky G.
  • Wieser M.
  • Olivieri A.
  • Plainaki C.
  • Ho G.
  • Killen R.
  • Slavin J.
  • Wurz P.
  • Berthelier Jean-Jacques
  • Dandouras I.
  • Kallio E.
  • Mckenna-Lawlor S.
  • Szalai S.
  • Torkar K.
  • Vaisberg O.
  • Allegrini F.
  • Daglis I.
  • Dong C.
  • Escoubet C.
  • Fatemi S.
  • Fränz M.
  • Ivanovski S.
  • Krupp N.
  • Lammer H.
  • Leblanc François
  • Mangano V.
  • Mura A.
  • Nilsson H.
  • Raines J.
  • Rispoli R.
  • Sarantos M.
  • Smith H.
  • Szego K.
  • Aronica A.
  • Camozzi F.
  • Di Lellis A.
  • Fremuth G.
  • Giner F.
  • Gurnee R.
  • Hayes J.
  • Jeszenszky H.
  • Tominetti F.
  • Trantham B.
  • Balaz J.
  • Baumjohann W.
  • Brienza D.
  • Bührke U.
  • Bush M.
  • Cantatore M.
  • Cibella S.
  • Colasanti L.
  • Cremonese G.
  • Cremonesi L.
  • D’alessandro M.
  • Delcourt Dominique
  • Delva M.
  • Desai M.
  • Fama M.
  • Ferris M.
  • Fischer H.
  • Gaggero A.
  • Gamborino D.
  • Garnier P.
  • Gibson W.
  • Goldstein R.
  • Grande M.
  • Grishin V.
  • Haggerty D.
  • Holmström M.
  • Horvath I.
  • Hsieh K.-C.
  • Jacques A.
  • Johnson R.
  • Kazakov A.
  • Kecskemety K.
  • Krüger H.
  • Kürbisch C.
  • Lazzarotto F.
  • Leblanc Frederic
  • Leichtfried M.
  • Leoni R.
  • Loose A.
  • Maschietti D.
  • Massetti S.
  • Mattioli F.
  • Miller G.
  • Moissenko D.
  • Morbidini A.
  • Noschese R.
  • Nuccilli F.
  • Nunez C.
  • Paschalidis N.
  • Persyn S.
  • Piazza D.
  • Oja M.
  • Ryno J.
  • Schmidt W.
  • Scheer J.
  • Shestakov A.
  • Shuvalov S.
  • Seki K.
  • Selci S.
  • Smith K.
  • Sordini R.
  • Svensson J.
  • Szalai L.
  • Toublanc D.
  • Urdiales C.
  • Varsani A.
  • Vertolli N.
  • Wallner R.
  • Wahlstroem P.
  • Wilson P.
  • Zampieri S.
  Space Science Reviews, Springer Verlag, 2021, 217 (2). (10.1007/s11214-021-00809-8)
  DOI : 10.1007/s11214-021-00809-8
• MMS Observations of the Multiscale Wave Structures and Parallel Electron Heating in the Vicinity of the Southern Exterior Cusp
  
  • Nykyri K.
  • Ma X.
  • Burkholder B.
  • Rice R.
  • Johnson J.
  • Kim E‐k.
  • Delamere P.
  • Michael A.
  • Sorathia K.
  • Lin D.
  • Merkin S.
  • Fuselier S.
  • Broll J.
  • Le Contel O.
  • Gershman D.
  • Cohen I.
  • Giles B.
  • Strangeway R.
  • Russell C.
  • Burch J.
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2021, 126 (3). (10.1029/2019JA027698)
  DOI : 10.1029/2019JA027698
• Sustainable improvement of seeds vigor using dry atmospheric plasma priming: Evidence through coating wettability, water uptake, and plasma reactive chemistry
  
  • Dufour Thierry
  • Gutierrez Q.
  • Bailly C
  Journal of Applied Physics, American Institute of Physics, 2021, 129 (8), pp.084902. (10.1063/5.0037247)
  DOI : 10.1063/5.0037247
• Whistler and Broadband Electrostatic Waves in the Multiple X‐Line Reconnection at the Magnetopause
  
  • Zhong Z.
  • Graham D.
  • Khotyaintsev Yu.
  • Zhou M.
  • Le Contel O.
  • Tang R.
  • Deng X.
  Geophysical Research Letters, American Geophysical Union, 2021, 48 (4). (10.1029/2020GL091320)
  DOI : 10.1029/2020GL091320
• Foundations of capacitive and inductive radio-frequency discharges
  
  • Chabert Pascal
  • Tsankov Tsanko Vaskov
  • Czarnetzki Uwe
  Plasma Sources Science and Technology, IOP Publishing, 2021, 30 (2), pp.024001. (10.1088/1361-6595/abc814)
  DOI : 10.1088/1361-6595/abc814
• The Dynamics of a High Mach Number Quasi-perpendicular Shock: MMS Observations
  
  • Madanian H.
  • Desai M.
  • Schwartz S.
  • Wilson L.
  • Fuselier S.
  • Burch J.
  • Contel O. Le
  • Turner D.
  • Ogasawara K.
  • Brosius A.
  • Russell C.
  • Ergun R.
  • Ahmadi N.
  • Gershman D.
  • Lindqvist P.-A.
  The Astrophysical Journal, American Astronomical Society, 2021, 908 (1), pp.40. (10.3847/1538-4357/abcb88)
  DOI : 10.3847/1538-4357/abcb88
• Interplanetary sheaths driven by magnetic clouds and their impact on Earth's magnetosheath
  
  • Moissard C.
  , 2021. The Sun often ejects large quantities of magnetic field embedded plasma called magnetic clouds. These can collide with the geomagnetic environment and sometimes perturb it to the point of causing dysfunctions in human technologies. When magnetic clouds travel fast enough, they can generate a shock, itself followed by a turbulent compressed stream named a sheath. Sheaths have recently been recognised as efficient drivers of geomagnetic activity. However, sheaths themselves and their interaction with the geomagnetic environment remain poorly known. First, by making a statistical study on satellite data of 42 relatively well-isolated sheaths, our work is the first to provide values of power and compressibility (which is an indication of the type of fluctuations) in sheaths. We also show the main parameters on which these two quantities depend. Second, we perform the first-ever 3D hybrid PIC simulation to include both an interplanetary shock/sheath self-consistently formed and a model of the geomagnetic environment. From this simulation, we show: the “rebound” of the bow shock's motion after its interaction with the interplanetary shock (a known phenomenon) can be explained by a counter streaming flow of subalfvénic particles bouncing back on the magnetopause; the interplanetary shock can be accelerated on the flanks of the magnetopause in the plane perpendicular to the interplanetary magnetic field; an important velocity component perpendicular to the interplanetary magnetic field rises in the sheath, leading to a strong asymmetry in the magnetosheath’s compression. We will conclude by discussing how our observational results could be used to guide efforts in future numerical simulations.
• Statistical Analysis of Magnetic Field Fluctuations in Coronal Mass Ejection-Driven Sheath Regions
  
  • Kilpua E.
  • Good S.
  • Ala-Lahti M.
  • Osmane A.
  • Fontaine Dominique
  • Hadid L. Z.
  • Janvier M.
  • Yordanova E.
  Frontiers in Astronomy and Space Sciences, Frontiers Media, 2021, 7. We report a statistical analysis of magnetic field fluctuations in 79 coronal mass ejection- (CME-) driven sheath regions that were observed in the near-Earth solar wind. Wind high-resolution magnetic field data were used to investigate 2 h regions adjacent to the shock and ejecta leading edge (Near-Shock and Near-LE regions, respectively), and the results were compared with a 2 h region upstream of the shock. The inertial-range spectral indices in the sheaths are found to be mostly steeper than the Kolmogorov −5/3 index and steeper than in the solar wind ahead. We did not find indications of an f − 1 spectrum, implying that magnetic fluctuation properties in CME sheaths differ significantly from planetary magnetosheaths and that CME-driven shocks do not reset the solar wind turbulence, as appears to happen downstream of planetary bow shocks. However, our study suggests that new compressible fluctuations are generated in the sheath for a wide variety of shock/upstream conditions. Fluctuation properties particularly differed between the Near-Shock region and the solar wind ahead. A strong positive correlation in the mean magnetic compressibility was found between the upstream and downstream regions, but the compressibility values in the sheaths were similar to those in the slow solar wind (<0.2), regardless of the value in the preceding wind. However, we did not find clear correlations between the inertial-range spectral indices in the sheaths and shock/preceding solar wind properties, nor with the mean normalized fluctuation amplitudes. Correlations were also considerably lower in the Near-LE region than in the Near-Shock region. Intermittency was also considerably higher in the sheath than in the upstream wind according to several proxies, particularly so in the Near-Shock region. Fluctuations in the sheath exhibit larger rotations than upstream, implying the presence of strong current sheets in the sheath that can add to intermittency. (10.3389/fspas.2020.610278)
  DOI : 10.3389/fspas.2020.610278
• Solar wind / magnetosphere coupling inferred from machine-learning methods
  
  • Nguyen Gautier
  , 2021. Decades of in-situ data measurement by missions focused on the study of the solar wind and its relation with the near-Earth environment allowed the study of the Sun-Earth coupling from a statistical point of view. Nevertheless, these studies are limited by the manual selection of the events of interest in the data that is still a subjective, fastidious and hardly reproducible task.Using machine learning algorithms, we elaborate automatic detection methods of events from in-situ data measurement. Whether they are applied to the detection of interplanetary coronal mass ejections, to the classification of the near-Earth regions or to the identification of magnetopause magnetic reconnection jets, the developed methods are more accurate than those based on manual, empirical thresholds. They are also adaptable from a mission to another provided the regions visited by the spacecraft are of the same nature. We show that the interpretation of the data by these methods is limited by the vision we have on the data and the events they measure.These methods pave the way for statistical studies of in-situ measured events with an important number of samples. Thereby, we use the classification of the different regions of the near-Earth environment to statistically study the position and shape of the magnetopause using the data of missions with equatorial (THEMIS, MMS, Double Star), polar (Cluster) and lunar (ARTEMIS) orbits. In addition to confirming the seasonal dependence, the azimuthal asymmetry and the influence of the solar wind dynamic pressure, we show that the clock angle of the interplanetary magnetic field modifies the shape of the magnetopause through the process of magnetic reconnection and lead a discussion on the nature of this boundary around the polar cusps. We combine the results of the study into an analytical model of the magnetopause position and shape that offers a more precise description of this boundary on the night side of the Earth magnetosphere.
• Ground‐Based GNSS and C/NOFS Observations of Ionospheric Irregularities Over Africa: A Case Study of the 2013 St. Patrick’s Day Geomagnetic Storm
  
  • Amaechi Paul O
  • Oyeyemi E. O
  • Akala A. O
  • Messanga H. E
  • Panda S. K
  • Seemala Gopi K
  • Oyedokun J. O
  • Fleury Rolland
  • Amory-Mazaudier Christine
  Space Weather: The International Journal of Research and Applications, American Geophysical Union (AGU), 2021, 19 (2). In this paper, the variations of ionospheric irregularities have been studied using C/NOFS, ground-based GNSS and magnetometer measurements in Africa during the St. Patrick geomagnetic storm of 17 March 2013. The latitudinal distribution of irregularities was examined using GNSS-ROTI maps covering longitude 25 o-45 o E. Longitudinal characteristics were also investigated along with equatorial plasma bubbles (EPBs) and vertical drift velocity (Vz) from 12-21 March 2013. The results show postsunset irregularities from 12 o S-27 o N with the stronger ones confined within 1 o S-7 o S and 12 o N-22 o N in the prestorm period. The observed pre-reversal enhancement (PRE) with Vz varying from 22.51-59.47 m/s between 20.26-20.86 LT corresponded with the occurrence of EPBs. PRE greater than 40 m/s nevertheless, supported long lasting depletions. During the main phase, prompt penetration electric field enhanced the PRE thus, extended the latitudinal range of irregularities to 31 o N. It also induced a long duration EPB along 15 o E and several depletions over the Eastern sector. During the recovery phase, stormtime wind drove a conspicuous asymmetry in the morphology of the postsunset anomaly. This corresponded with the reduction in the latitudinal extent and strength of irregularities. Westward/eastward disturbance dynamo electric field inhibited/triggered irregularities in the postsunset/ postmidnight period on 18 March over the Eastern sector. The difference in the drift accounted for the longitudinal variations of irregularities before the storm. During the main phase however, irregularities were present (reduced) over the Eastern (Atlantic/Western) sectors. This difference might have been related to the changes in the wind inferred from the anomaly shape. (10.1029/2020SW002631)
  DOI : 10.1029/2020SW002631
• SERENA: Particle Instrument Suite for Determining the Sun-Mercury Interaction from BepiColombo
  
  • Orsini Stefano
  • Livi S. A.
  • Lichtenegger H.
  • Barabash S.
  • Milillo A.
  • Angelis E. De
  • Phillips M.
  • Laky G.
  • Wieser M.
  • Olivieri A.
  • Plainaki C.
  • Ho G.
  • Killen R. M.
  • Slavin J. A.
  • Wurz P.
  • Berthelier Jean-Jacques
  • Dandouras I.
  • Kallio E.
  • Mckenna-Lawlor S.
  • Szalai S.
  • Torkar K.
  • Vaisberg O.
  • Allegrini F.
  • Daglis I. A.
  • Dong C.
  • Escoubet C. P.
  • Fatemi S.
  • Fränz M.
  • Ivanovski S.
  • Krupp N.
  • Lammer H.
  • Leblanc François
  • Mangano V.
  • Mura A.
  • Nilsson H.
  • Raines J. M.
  • Rispoli R.
  • Sarantos M.
  • Smith H. T.
  • Szego K.
  • Aronica A.
  • Camozzi F.
  • Di Lellis A. M.
  • Fremuth G.
  • Giner F.
  • Gurnee R.
  • Hayes J.
  • Jeszenszky H.
  • Tominetti F.
  • Trantham B.
  • Balaz J.
  • Baumjohann W.
  • Brienza D.
  • Buhrke U.
  • Bush M. D.
  • Cantatore M.
  • Cibella S.
  • Colasanti L.
  • Cremonese Gabriele
  • Cremonesi L.
  • D’alessandro M.
  • Delcourt Dominique
  • Delva M.
  • Desai M.
  • Fama M.
  • Ferris M.
  • Fischer H.
  • Gaggero A.
  • Gamborino D.
  • Garnier P.
  • Gibson W. C.
  • Goldstein R.
  • Grande M.
  • Grishin V.
  • Haggerty D.
  • Holmström M.
  • Horvath I.
  • Hsieh K.-C.
  • Jacques A.
  • Johnson R. E.
  • Kazakov A.
  • Kecskemety K.
  • Krüger H.
  • Kürbisch C.
  • Lazzarotto F.
  • Leblanc Frederic
  • Leichtfried M.
  • Leoni R.
  • Loose A.
  • Maschietti D.
  • Massetti S.
  • Mattioli F.
  • Miller G.
  • Moissenko D.
  • Morbidini A.
  • Noschese R.
  • Nuccilli F.
  • Nunez C.
  • Paschalidis N.
  • Persyn S.
  • Piazza D.
  • Oja M.
  • Rynö J.
  • Schmidt W.
  • Scheer J. A.
  • Shestakov A.
  • Shuvalov S.
  • Seki K.
  • Selci S.
  • Smith K.
  • Sordini R.
  • Svensson J.
  • Szalai L.
  • Toublanc D.
  • Urdiales C.
  • Varsani A.
  • Vertolli N.
  • Wallner R.
  • Wahlstroem P.
  • Wilson P.
  • Sampieri S.
  Space Science Reviews, Springer Verlag, 2021, 217 (1), pp.11. The ESA-JAXA BepiColombo mission to Mercury will provide simultaneous measurements from two spacecraft, offering an unprecedented opportunity to investigate magnetospheric and exospheric particle dynamics at Mercury as well as their interactions with solar wind, solar radiation, and interplanetary dust. The particle instrument suite SERENA (Search for Exospheric Refilling and Emitted Natural Abundances) is flying in space on-board the BepiColombo Mercury Planetary Orbiter (MPO) and is the only instrument for ion and neutral particle detection aboard the MPO. It comprises four independent sensors: ELENA for neutral particle flow detection, Strofio for neutral gas detection, PICAM for planetary ions observations, and MIPA, mostly for solar wind ion measurements. SERENA is managed by a System Control Unit located inside the ELENA box. In the present paper the scientific goals of this suite are described, and then the four units are detailed, as well as their major features and calibration results. Finally, the SERENA operational activities are shown during the orbital path around Mercury, with also some reference to the activities planned during the long cruise phase. (10.1007/s11214-020-00787-3)
  DOI : 10.1007/s11214-020-00787-3
• Study of the electric field in a diffuse nanosecond positive ionization wave generated in a pin-to-plane geometry in atmospheric pressure air
  
  • Bourdon Anne
  • Péchereau François
  • Tholin Fabien
  • Bonaventura Zdenek
  Journal of Physics D: Applied Physics, IOP Publishing, 2021, 54. The dynamics of a nanosecond positive ionization front generated in a pin-to-plane geometry in atmospheric pressure air is simulated using a 2D axisymmetric drift-diffusion fluid model. For a 16 mm gap and a sharp pin electrode, the plateau of the applied voltage is varied between 40 and 60 kV and the rise time is varied between 0.5 and 1.5 ns or a DC voltage is applied. The discharge ignition time and the voltage at ignition are shown to depend mostly on the voltage rise time. The connection time, i.e. the time for the ionization wave to ignite, propagate and connect to the plane is shown to strongly depend on both the values of the voltage plateau and rise time. For all cases, the discharge has a conical shape with a maximal radius of about 8 mm as it connects to the grounded plane. The average propagation velocity of the ionization front is found to vary in the range 3.1 to 8.5 mm ns−1. These values are in rather good agreement with experiments. Temporal evolutions of the electric field are recorded on the symmetry axis at different positions in the gap. At each location, an increase and decrease of the electric field is observed as the ionization front, propagating from the pin to the plane, passes the studied point, in accordance with experimental observations. Finally, for a voltage plateau of 55 kV and a rise time of 0.5 ns, a temporal sampling of 100 ps is shown to be sufficient to capture the dynamics of the electric field during the ionization front propagation when it passes close to the middle of the gap. Conversely, a temporal sampling of 10 ps is required when the ionization wave is close to both electrodes, or during the fast redistribution of the electric field after the connection of the ionization front at the cathode. (10.1088/1361-6463/abbc3a)
  DOI : 10.1088/1361-6463/abbc3a
• In Situ Evidence of Ion Acceleration between Consecutive Reconnection Jet Fronts
  
  • Catapano Filomena
  • Retinò Alessandro
  • Zimbardo Gaetano
  • Alexandrova Alexandra
  • Cohen Ian J
  • Turner Drew L
  • Le Contel Olivier
  • Cozzani Giulia
  • Perri Silvia
  • Greco Antonella
  • Breuillard Hugo
  • Delcourt Dominique
  • Mirioni Laurent
  • Khotyaintsev Yuri
  • Vaivads Andris
  • Giles Barbara L
  • Mauk Barry H
  • Fuselier Stephen A
  • Torbert Roy B
  • Russell Christopher T
  • Lindqvist Per A
  • Ergun Robert E
  • Moore Thomas
  • Burch James L
  The Astrophysical Journal, American Astronomical Society, 2021, 908 (1), pp.73. Processes driven by unsteady reconnection can efficiently accelerate particles in many astrophysical plasmas. An example is the reconnection jet fronts in an outflow region. We present evidence of suprathermal ion acceleration between two consecutive reconnection jet fronts observed by the Magnetospheric Multiscale mission in the terrestrial magnetotail. An earthward propagating jet is approached by a second faster jet. Between the jets, the thermal ions are mostly perpendicular to magnetic field, are trapped, and are gradually accelerated in the parallel direction up to 150 keV. Observations suggest that ions are predominantly accelerated by a Fermi-like mechanism in the contracting magnetic bottle formed between the two jet fronts. The ion acceleration mechanism is presumably efficient in other environments where jet fronts produced by variable rates of reconnection are common and where the interaction of multiple jet fronts can also develop a turbulent environment, e.g., in stellar and solar eruptions. (10.3847/1538-4357/abce5a)
  DOI : 10.3847/1538-4357/abce5a
• Observation of an inertial-range energy cascade within a reconnection jet in the Earth’s magnetotail
  
  • Bandyopadhyay Riddhi
  • Chasapis A.
  • Gershman D
  • Giles B
  • Russell C
  • Strangeway R
  • Le Contel O
  • Argall M
  • Burch J
  Monthly Notices of the Royal Astronomical Society: Letters, Oxford Journals, 2021, 500 (1), pp.L6-L10. (10.1093/mnrasl/slaa171)
  DOI : 10.1093/mnrasl/slaa171
• Comparison between kinetic theory and PIC simulations of anomalous electron transport in E x B plasma discharges
  
  • Charoy Thomas
  • Lafleur Trevor
  • Alvarez-Laguna Alejandro
  • Bourdon Anne
  • Chabert Pascal
  , 2021.
• The Plasma Observatory: exploring particle energization in space plasmas through multi-point, multi-scale in situ measurements
  
  • Retino Alessandro
  , 2021, 43. Understanding particle energization in plasmas is a compelling science problem of major importance for the worldwide magnetospheric, solar, and astrophysical plasma communities. In situ measurements are required to study and understand how particles are energized in space plasmas. In the solar system, the near-Earth space is an unique laboratory for studying particle energization since very high resolution in situ measurements can be performed and all data can be transmitted to ground with high cadence. Furthermore, the near-Earth space provides a wide range of different plasma conditions, which can be used as a proxy for solar and astrophysical plasma regimes. This presentation outlines the importance of studying particle energization through future multi-point, multi-scale in situ measurements. Five compelling science questions related to particle energization by shocks, reconnection, waves and turbulence, jets and their combinations, are identified. Answering these questions requires resolving scale coupling, nonlinearity and non-stationarity, which cannot be done with existing 4-point observations. In situ measurements from a multi-point, multi-scale Plasma Observatory consisting of at least 7 spacecraft are needed, covering fluid, ion and electron scales. Such a novel Plasma Observatory will enable a paradigm shift in our comprehension of particle energization processes with very important impact on solar and astrophysical plasmas. The ideas discussed in this presentation are included in the White Paper « Particle Energization in Space Plasmas: Towards a Multi-Point, Multi-Scale Plasma Observatory » which has been submitted for the future ESA Voyage 2035-2050 science program.
• Zonal instability and wave trapping
  
  • Garbet Xavier
  • Panico O
  • Varennes R
  • Gillot C
  • Dif-Pradalier Guilhem
  • Sarazin Y
  • Bourne E
  • Grandgirard V
  • Ghendrih P
  • Zarzoso D
  • Vermare L
  Journal of Physics: Conference Series, IOP Science, 2021. This paper presents a model for zonal flow generation based on a wave kinetic equation coupled to a poloidal momentum equation in a regime where wave trapping matters. Several models of the wave collision operator have been tested: Krook, diffusion and diffusion plus an instability growth rate. Conditions for zonal instability have been identified. It is found that a zonal instability is possible in all cases. However the force is a power law of the zonal velocity, so different from the quasi-linear case of random phases that produces a force that is linear in velocity. Also the zonal force may change sign, leading to flow radial profiles that are not sinusoidal.
• Statistical Characteristics in the Spectrum of Whistler Waves Near the Diffusion Region of Dayside Magnetopause Reconnection
  
  • Ren Y.
  • Dai L.
  • Wang C.
  • Li W.
  • Tao X.
  • Lavraud B.
  • Le Contel O.
  Geophysical Research Letters, American Geophysical Union, 2021, 48 (1). (10.1029/2020GL090816)
  DOI : 10.1029/2020GL090816
• Spectral micro-scale measurements of the initial stage of streamer-to-filament transition in high pressure nanosecond surface dielectric barrier discharge
  
  • Ding Chenyang
  • Jean Antonin
  • Popov Nicolay
  • Starikovskaia Svetlana
  , 2021. The paper presents the recent study of spectral composition of the filament during its propagation process in the single shot surface nanosecond dielectric barrier discharge (nSDBD) at high pressures. The micro-images and spectra at specific moments were recorded by the ICCD camera and spectrometer accompanied with the long distance microscope. This is the first time that we analysis nSDBD in the micrometer scale. The discharge starts with the streamer generated from the high-voltage electrode. A few nanoseconds later, there are a few protrusions passing through the streamer front. After the protrusions' propagation, the filaments are formed in the whole channel connecting the high-voltage electrode and the tip of protrusions. It is found that in the early stage of the streamer-to-filament transition, both the streamer and the protrusion are contributed by the second positive system of nitrogen while only when the whole filament is formed, the cw emission can be seen. (10.2514/6.2021-1699)
  DOI : 10.2514/6.2021-1699
• Parametric study of a moderate pressure nanosecond discharge to reduce detonation cell width
  
  • Ali Cherif Mhedine
  • Catoire Laurent
  • Vidal Pierre
  • Claverie Alain
  • Starikovskaia Svetlana M
  , 2021. The effect of a volumetric nanosecond discharge on detonation cell size was demonstrated experimentally in a detonation tube test rig. The experiments were performed in CH 4 :O 2 :Ar=1:2:2 mixture, at initial pressure 180 mbar and ambient temperature. The detonation wave was initiated in a 3.6-m long, 50 × 50-mm 2 square cross section tube, and entered the measuring section where the electrode system was installed to produce a double-pulse discharge ahead of the detonation front. The triggering of the discharge was synchronized with the arrival of the detonation front to the diagnostic chamber. The plasma was generated by two consecutive pulses of −50 and −32 kV amplitude on the high-voltage electrode and 25 ns pulse duration. It was shown that the plasma fills the entire interelectrode space. The analysis of the detonation cell size with and without plasma generation was performed via sooted-plate technique. Production of atoms and radicals in the discharge triggered combustion chemistry decreasing the ignition delay time. As a result, the detonation cell size was reduced by a factor of 1.5 − 2, while passing through the region of the discharge. (10.2514/6.2021-1789)
  DOI : 10.2514/6.2021-1789
• Thin Current Sheet Behind the Dipolarization Front
  
  • Nakamura Rumi
  • Baumjohann W.
  • Nakamura T. K M
  • Panov E. V
  • Schmid D.
  • Varsani A.
  • Apatenkov S.
  • Sergeev V. A
  • Birn J.
  • Nagai T.
  • Gabrielse C.
  • André M.
  • Burch J. L
  • Carr C.
  • Dandouras I. S
  • Escoubet C. P
  • Fazakerley N.
  • Giles B. L
  • Le Contel O.
  • Russell C. T
  • Torbert R. B
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2021, 126 (10), pp.e2021JA029518. We report a unique conjugate observation of fast flows and associated current sheet disturbances in the near-Earth magnetotail by MMS (Magnetospheric Multiscale) and Cluster preceding a positive bay onset of a small substorm at ∼14:10 UT, September 8, 2018. MMS and Cluster were located both at X ∼ −14 RE. A dipolarization front (DF) of a localized fast flow was detected by Cluster and MMS, separated in the dawn-dusk direction by ∼4 RE, almost simultaneously. Adiabatic electron acceleration signatures revealed from the comparison of the energy spectra confirm that both spacecraft encounter the same DF. We analyzed the change in the current sheet structure based on multi-scale multi-point data analysis. The current sheet thickened during the passage of DF, yet, temporally thinned subsequently associated with another flow enhancement centered more on the dawnward side of the initial flow. MMS and Cluster observed intense perpendicular and parallel current in the off-equatorial region mainly during this interval of the current sheet thinning. Maximum field-aligned currents both at MMS and Cluster are directed tailward. Detailed analysis of MMS data showed that the intense field-aligned currents consisted of multiple small-scale intense current layers accompanied by enhanced Hall-currents in the dawn-dusk flow-shear region. We suggest that the current sheet thinning is related to the flow bouncing process and/or to the expansion/activation of reconnection. Based on these mesoscale and small-scale multipoint observations, 3D evolution of the flow and current-sheet disturbances was inferred preceding the development of a substorm current wedge. (10.1029/2021JA029518)
  DOI : 10.1029/2021JA029518
• A differential approximation model for passive scalar turbulence
  
  • Morel Pierre
  • Xu Shaokang
  • Gürcan Özgür D.
  Journal of Physics A: Mathematical and Theoretical, IOP Publishing, 2021, 54 (33), pp.335701. Two dimensional passive scalar turbulence is studied by means of a k-space diffusion model based on a third order differential approximation. This simple description of local nonlinear interactions in Fourier space is shown to present a general expression, in line with previous seminal works, and appears to be suitable for various 2D turbulence problems. Steady state solutions for the spectral energy density of the flow is shown to recover the Kraichnan-Kolmogorov phenomenology of the dual cascade, while various passive scalar spectra, such as Batchelor or Obukhov-Corssin spectra are recovered as steady state solutions of the spectral energy density of the passive scalar. These analytical results are then corroborated by numerical solutions of the time evolving problem with energy and passive scalar injection and dissipation on a logarithmic wavenumber space grid over a large range of scales. The particular power law spectra that is obtained is found to depend mainly on the location of the kinetic and passive scalar energy injections. (10.1088/1751-8121/ac1484)
  DOI : 10.1088/1751-8121/ac1484
• Chemical kinetics and density measurements of OH in an atmospheric pressure He + O2 + H2O radiofrequency plasma
  
  • Brisset Alexandra
  • Gibson Andrew
  • Schröter Sandra
  • Niemi Kari
  • Booth Jean-Paul
  • Gans Timo
  • O'Connell Deborah
  • Wagenaars Erik
  Journal of Physics D: Applied Physics, IOP Publishing, 2021, 54 (28), pp.285201. This work presents experiments and modelling of OH densities in a radio-frequency driven atmospheric-pressure plasma in a plane-parallel geometry, operated in helium with small admixtures of oxygen and water vapour (He + O2 + H2O). The density of OH is measured under a wide range of conditions by absorption spectroscopy, using an ultra-stable laser-driven broad-band light source. These measurements are compared with 0D plasma chemical kinetics simulations adapted for high levels of O2 (1%). Without O2 admixture, the measured density of OH increases from 1.0 × 1014 to 4.0 × 1014 cm−3 for H2O admixtures from 0.05% to 1%. The density of atomic oxygen is about 1 × 1013 cm−3 and grows with humidity content. With O2 admixture, the OH density stays relatively constant, showing only a small maximum at 0.1% O2. The simulations predict that the atomic oxygen density is strongly increased by O2 addition. It reaches ~1015 cm−3 without humidity, but is limited to ~1014 cm−3 beyond 0.05% water content. The addition of O2 has a weak effect on the OH density because, while atomic oxygen becomes a dominant precursor for the formation of OH, it makes a nearly equal contribution to the loss processes of OH. The small increase in the density of OH with the addition of O2 is instead due to reaction pathways involving increased production of HO2 and O3. The simulations show that the densities of OH, O and O3 can be tailored relatively independently over a wide range of conditions. The densities of O and O3 are strongly affected by the presence of small quantities (0.05%) of water vapour, but further water addition has little effect. Therefore, a greater range and control of the reactive species mix from the plasma can be obtained by the use of well-controlled multiple gas admixtures, instead of relying on ambient air mixing. (10.1088/1361-6463/abefec)
  DOI : 10.1088/1361-6463/abefec