Publications

2022

• Parker Solar Probe
  
  • Hadid Lina L. Z. Hadid
  • Witasse Olivier
  , 2022, pp.1-3. (10.1007/978-3-642-27833-4_5557-1)
  DOI : 10.1007/978-3-642-27833-4_5557-1
• Ionospheric Response to the Coronal Hole Activity of August 2020: A Global Multi‐Instrumental Overview
  
  • Younas Waqar
  • Khan Majid
  • Amory‐mazaudier C
  • Amaechi P O
  Space Weather: The International Journal of Research and Applications, American Geophysical Union (AGU), 2022, 20 (12). We have studied the ionospheric response to a coronal hole event of August 2020 using the data from global ionospheric maps, ground magnetometers and parameters from the instruments onboard SWARM and thermosphere, ionosphere, mesosphere energetics and dynamics satellites. The role of different physical drivers, responsible for observed ionospheric disturbance, has been identified. On the storm day (2 August), a steady southward directed interplanetary magnetic field B z caused the penetration of magnetospheric convection electric field and positive storm effect in daytime sectors. As a result of prompt penetration electric field (PPEF) on 2 August, a polar‐ward expansion of day‐side ionospheric plasma. On 3 August, the signatures of both disturbance dynamo electric field (DDEF) caused by disturbed thermospheric winds and PPEF have been observed. The westward PPEF and eastward disturbance DDEF on the night‐side caused a strong enhancement in ionospheric plasma parameters at the corresponding sectors. The effect of disturbed thermospheric winds and resultant electric field persisted till the end of 7 August. The large decrease in O/N 2 ratio at northern mid‐latitudes which is a consequence of the seasonal impact resulted in the negative storm effects at corresponding latitudinal regions. This study has shown that although the storm of August 2020 was a minor one, the associated high speed solar wind streams emanating from a coronal hole resulted in drastic changes in ionospheric parameters including global electron content, in situ electron density and total electron content at the equatorial ionization anomaly and equatorial electric field. (10.1029/2022SW003176)
  DOI : 10.1029/2022SW003176
• Numerical investigation of spallation neutrons generated from petawatt-scale laserdriven proton beams
  
  • Martinez B
  • Chen S N
  • Bolaños S
  • Blanchot N
  • Boutoux G
  • Cayzac W
  • Courtois C
  • Davoine X
  • Duval A
  • Horny V
  • Lantuejoul I
  • Le Deroff L
  • Masson-Laborde P E
  • Sary G
  • Vauzour B
  • Smets Roch
  • Gremillet L
  • Fuchs J
  Matter and Radiation at Extremes, AIP Publishing, 2022, 7, pp.024401. Laser-driven neutron sources could offer a promising alternative to those based on conventional accelerator technologies in delivering compact beams of high brightness and short duration. We examine this through particle-in-cell and Monte Carlo simulations, that model, respectively, the laser acceleration of protons from thin-foil targets and their subsequent conversion into neutrons in secondary lead targets. Laser parameters relevant to the 0.5 petawatt (PW) LMJ-PETAL and 0.6-6 PW Apollon systems are considered. Due to its high intensity, the 20-fs-duration 0.6 PW Apollon laser is expected to accelerate protons up to above 100 MeV, thereby unlocking efficient neutron generation via spallation reactions. As a result, despite a 30-fold lower pulse energy than the LMJ-PETAL laser, the 0.6 PW Apollon laser should perform comparably well both in terms of neutron yield and flux. Notably, we predict that very compact neutron sources, of ~ 10 ps duration and ~ 100 µm spot size, can be released provided the lead convertor target is thin enough (~ 100 µm). These sources are characterized by extreme fluxes, of the order of 10$^{23}$ n cm$^{-2}$ s$^{-1}$ , and even ten times higher when using the 6 PW Apollon laser. Such values surpass those currently achievable at large-scale accelerator-based neutron sources (~ 10$^{16}$ n cm$^{-2}$ s$^{-1}$), or reported from previous laser experiments using low-Z converters (~ 10$^{18}$ n cm$^{-2}$ s$^{-1}$). By showing that such laser systems can produce neutron pulses significantly brighter than existing sources, our findings open a path towards attractive novel applications, such as flash neutron radiography or laboratory studies of heavy-ion nucleosynthesis. (10.1063/5.0060582)
  DOI : 10.1063/5.0060582
• Energy Conversion Processes related to Dipolarization Fronts in the Earth’s magnetotail
  
  • Alqeeq Soboh
  , 2022. Fast plasma flows have been detected in the nightside of the Earth's magnetosphere, the magnetotail, for a long time. Different processes such as magnetic reconnection or kinetic ballooning-interchange instability are still investigated. While propagating Earthward, these flows generate a sharp increase of the northward component of the magnetic field named dipolarisation front (DF). These kinetic scale structures contribute significantly to the energy dissipation in the magnetosphere. This study aims at better understanding the energy conversion processes described by J · E (J being the current density and E the electric field) which occur in the vicinity of these fronts and at determining their role in the energy global cycle of the magnetosphere. Using in situ measurements from the Magnetospheric Multiscale mission, which consists of four identical satellites evolving in a tetrahedral configuration and separated at electron scales, I have first investigated the current density structures, the different terms of the Ohm's law, and the energy conversion processes for 6 DFs. I found that for all DFs, ions are mainly decoupled from the magnetic field by the Hall electric field but the electron pressure gradient also contributes. It implies that electrons are decoupled by their own pressure gradient at DF. Regarding the energy conversion processes in the spacecraft frame, the energy is transferred from the electromagnetic fields to the plasma ahead of the DF (dissipation or loading region) whereas it is transferred from the plasma to the fields (dynamo or generator region) behind the front. This energy conversion reversal is caused by the reversal of the ion diamagnetic current at DF. In the fluid frame, the energy is always transferred to the fields, due to the electric field generated by the electron pressure gradient, which could contribute to the slowdown of the flow. Furthermore, it is shown that the energy conversion processes are not homogeneous at the electron scale mostly due to the variations of the electric fields. These case study results have been extended thanks to a statistical study carried out over the full 2017 magnetotail season. From this study, it turns out that two DF classes can be distinguished: class I (74.4%) corresponds to the standard DF properties and energy dissipation whereas a new class II (25.6%), which includes the 6 DF previously discussed, corresponds to a bump of the magnetic field associated with a minimum of the ion and electron pressures and a reversal of the energy conversion process. The possible origin of this second class is discussed. For both DF classes, it is shown that the energy conversion process in the spacecraft frame is driven by the diamagnetic current dominated by the ion pressure gradient. In the fluide frame, it is driven by the electron pressure gradient.
• From incoherent field to coherent reconnection
  
  • Robinson Rebecca
  • Carlsson Mats
  • Aulanier Guillaume
  Astronomy & Astrophysics - A&A, EDP Sciences, 2022, 668, pp.A177. Context. Magnetic reconnection in the quiet Sun is a phenomenon that is consistently observed, however, its conditions of occurrence are not as well known as for more energetic events. It has recently become feasible to address this issue with 3D numerical simulations of realistically stratified and convection-driven reconnection. Aims. We aim to illustrate ways by which quiet Sun fields may contribute to solar atmospheric heating via magnetic reconnection that is driven by convective motion. We also aim to compare our complex stratified model to earlier idealized coronal models in terms of reconnection drivers and topological conditions. Methods. We analyzed a simulation of the quiet Sun in which a complex coronal magnetic field is self-consistently driven by the underlying convection. We employed a selection of Lagrangian markers to trace the spatiotemporal behavior of specific magnetic features that are relevant to magnetic reconnection and atmospheric heating. Results. A relatively large-scale reconnection-driven heating event occurs in the simulated corona, in a flattened X-shaped feature characterized by a weak field and high current. It is reminiscent of a hyperbolic flux tube (HFT), which is located at the interface between multiple flux systems. One of these is a smooth overlying horizontal field and the two most relevant others are located below the HFT. They consist of an arcade and a horizontal flux rope which eventually reconnect with the overlying field, raising coronal plasma temperatures up to 1.47 MK. Conclusions. We have identified a reconnection-driven coronal heating event in a quiet Sun simulation. We find that our results are in good phenomenological agreement with idealized coronal flare models, which demonstrates that the same general physical concepts are valid. However, we also find that the reconnecting flux rope and arcade are neither formed by any obvious coherent flux emergence, nor by any ordered photospheric motion or flux cancellation. Instead, they seem to develop merely from the self-consistent convective driving of pre-existing tangled field lines. This gradual and smooth ordering suggests an inverse cascade of magnetic helicity via smaller reconnection events, located at or above slowly-moving photospheric flux concentrations. We suggest that this case is representative of many heating events that may be ubiquitous in the real quiet Sun. (10.1051/0004-6361/202244750)
  DOI : 10.1051/0004-6361/202244750
• The Imprint of Intermittent Interchange Reconnection on the Solar Wind
  
  • Wyper Peter
  • Devore C.
  • Antiochos S.
  • Pontin D.
  • Higginson Aleida
  • Scott Roger
  • Masson Sophie
  • Pelegrin-Frachon Theo
  The Astrophysical Journal Letters, Bristol : IOP Publishing, 2022, 941 (2), pp.L29. Abstract The solar wind is known to be highly structured in space and time. Observations from Parker Solar Probe have revealed an abundance of so-called magnetic switchbacks within the near-Sun solar wind. In this Letter, we use a high-resolution, adaptive-mesh, magnetohydrodynamics simulation to explore the disturbances launched into the solar wind by intermittent/bursty interchange reconnection and how they may be related to magnetic switchbacks. We find that repeated ejection of plasmoid flux ropes into the solar wind produces a curtain of propagating and interacting torsional Alfvénic waves. We demonstrate that this curtain forms when plasmoid flux ropes dynamically realign with the radial field as they are ejected from the current layer and that this is a robust effect of the 3D geometry of the interchange reconnection region. Simulated flythroughs of this curtain in the low corona reveal an Alfvénic patch that closely resembles observations of switchback patches, but with relatively small magnetic field deflections. Therefore, we suggest that switchbacks could be the solar wind imprint of intermittent interchange reconnection in the corona, provided an in situ process subsequently amplifies the disturbances to generate the large deflections or reversals of radial field that are typically observed. That is to say, our results indicate that a combination of low-coronal and inner-heliospheric mechanisms may be required to explain switchback observations. (10.3847/2041-8213/aca8ae)
  DOI : 10.3847/2041-8213/aca8ae
• Étude des effets d’un plasma froid d’air ambiant sur la physiologie des graines d'Arabidopsis
  
  • August Jonas
  , 2022. Les plasmas froids d’air ambiant (PFA2) sont des gaz faiblement ionisés composés d’espèces réactives de l’oxygène et de l’azote, d’électrons libres énergétiques, d’espèces métastables et de photons dans les domaines spectraux UV et visible. En raison de leurs propriétés électriques, thermiques, radiatives et chimiques, ces procédés apparaissent pertinents pour améliorer les propriétés germinatives des semences. De plus, les plasmas froids sont une solution technologique prometteuse pour remplacer les produits agrochimiques et faire face aux problèmes de l'agriculture moderne. Les études menées pendant la thèse ont permis de comprendre les effets des PFA2 sur la physiologie des semences d’une espèce modèle en biologie : Arabidopsis thaliana. Une première étude a été menée pour comprendre comment la teneur en eau peut modifier les propriétés électriques des graines et leur interaction avec les propriétés du plasma froid. Puis, l’observation et l’analyse des modifications physiologiques des semences traitées par PFA2 ont permis (i) d’identifier les conditions biologiques et physiques optimales à la levée de dormance des semences et (ii) de lier ce phénomène à la transition vitreuse cytoplasmique des tissus de la graine. Enfin, pour comprendre les effets du plasma sur les propriétés germinatives des semences, les processus biologiques déclenchés après exposition au PFA2 ont été analysés de l’état sec à la phase d’imbibition des graines menant à la germination. Le rôle des réactions oxydatives, des changements anatomiques (évalués par tomographie), et de la régulation de l’expression des gènes ont été mis en évidence. Les résultats obtenus ont été corrélés et discutés afin d’expliciter les mécanismes régissant la levée de dormance et le changement d’état physiologique des graines d’Arabidopsis par le traitement au PFA2.
• Investigation of iodine plasmas for space propulsion applications
  
  • Esteves Benjamin
  , 2022. Since the 1960s, the most used gas for electric space propulsion has been xenon, a heavy atom that is easy to ionize. However, although it is a product of air distillation, which is a priori inexhaustible, the very low concentration of xenon in the atmosphere limits its annual production and the growing demand makes it necessary to find a sustainable alternative with comparable performance.Iodine, an element next to xenon in the periodic table, is a viable candidate to succeed it despite its molecular and electronegative nature. In this work, we try to understand how and why iodine, in its plasma state, can serenely consider the battle with its competitors, and in particular krypton, in the space race.The study of low-pressure iodine plasmas was conducted in two complementary directions.On the one hand, two experimental iodine plasma set-ups (a gridded-ion-thruster and a quartz cell) were set up and developed, within which numerous electrical and optical diagnostics (Langmuir probe, photodetachment of negative I- ions, absorption on excited atomic states, TALIF on the fundamental atomic level) were developed and successfully applied, some of them for the first time. These experimental works allowed us to measure the absolute values of different species of the plasma (electrons, negative I- ions, positive ions, molecules, population difference between the first two atomic states), to highlight the non-negligible presence of an excited atomic state at 0.94~eV, to shift all the excited atomic levels downwards by 0.167 cm-1 with respect to the reference spectroscopic table, or to measure the degree of molecular dissociation, approaching, for sufficient power, more than 95 %. Also, the temperature of the atoms was measured and heating mechanisms much more prevalent than in noble gas plasmas were brought to light and discussed.On the other hand, a rigorous bibliography on collisional data (census and questioning of the effective sections and reaction rates measured or calculated) of atomic and molecular iodine, allowed the development of numerical simulation tools aiming at reproducing the functioning of iodine plasmas. Firstly, a global model, averaged in volume and allowing the description of the essential characteristics of the plasma, was largely updated with the new set of cross-sections and enriched to take into account the heating of neutral species. Secondly, a one-dimensional multi-fluid model of the three major neutral species in an iodine plasma (atom in its ground state, first excited atomic state, and molecule) has been developed to simulate their densities, velocities, and temperatures along the thrust axis of the thruster. The inertia terms and heat fluxes of each species were taken into account.Comparisons between experiments and models proved to be relevant and led to several conclusions. At low injection flux or pressure (around 1 mTorr for our thruster), the plasma is fully dissociated. It behaves like a noble gas plasma, composed almost entirely of I atoms, positive I+ atomic ions, and electrons. It is in this operating regime, where dissociation is energetically inexpensive, that iodine can revolutionize the field of electric propulsion by being more efficient than its noble competitors (argon, krypton, and xenon) in producing ions, and thus generating better thrust. At higher rates, however, the molecules are no longer negligible and easily produce negative I- and molecular I2+ ions. Under these conditions, iodine is no longer competitive for propulsion, with krypton offering even better performance.
• Global 3D Hybrid Simulations of the Interaction between a Interplanetary Shock and the Terrestrial Bow-Shock / Magnetosheath Environment
  
  • Cazzola Emanuele
  • Fontaine D.
  • Savoini Philippe
  , 2022. Interplanetary Shocks are ubiquitous in the Solar System. They can be generated by a number of different sources, including Coronal Mass Ejections and Corotating Interaction Regions, whenever a fast stream overlays the slow background stream, forming a turbulent sheath downstream the discontinuity front. Given its highly compressed region, the Interplanetary Shocks can lead to a significant geoeffectiveness when directed towards the Earth. As such, the interaction between Interplanetary Shocks and the terrestrial Bow-Shock and Magnetosheath have been mainly studied with MHD simulations based on specific models. However, the MHD approach is not enough to capture some kinetic aspects of such interaction, including the interaction with a foreshock region, as well as the effects of the presence of kinetic-based magnetic and density oscillations on the Bow-Shock surface and in the Magnetosheath. In this work we present some results from global 3D hybrid simulations on the effects of an Interplanetary Shock and its self-consistently induced Sheath Region with a sudden Slow and Fast Solar Wind overlay on the Bow-Shock and Magnetosheath dynamics. In particular, we have observed that the presence of a foreshock region strongly affects the propagation of the discontinuity front both inside and outside the Magnetosheath. We show that the interaction between the Shock Sheath and the Bow-Shock generates the formation of new Quasi-Parallel and Quasi-Perpendicular regions eventually leading to the onset of new kinetic-based phenomena.
• Numerical modelling of mutual impedance probes and quasi thermal noise spectroscopy in a magnetized plasma
  
  • Dazzi Pietro
  • Henri Pierre
  • Issautier Karine
  • Bucciantini Luca
  , 2022.
• Moonraker: Enceladus Multiple Flyby Mission
  
  • Mousis Olivier
  • Bouquet Alexis
  • Langevin Yves
  • André N
  • Boithias Hélène
  • Durry Georges
  • Faye F.
  • Hartogh Paul
  • Helbert J.
  • Iess L
  • Kempf S
  • Masters A
  • Postberg F
  • Renard Jean-Baptiste
  • Vernazza P
  • Vorburger A
  • Wurz P
  • Atkinson D. H.
  • Barabash S
  • Berthomier M
  • Brucato J
  • Cable M
  • Carter John
  • Cazaux S
  • Coustenis A
  • Danger G
  • Dehant V
  • Fornaro T
  • Garnier Philippe
  • Gautier Thomas
  • Groussin O
  • Hadid L Z
  • Ize J-C
  • Kolmasova I
  • Lebreton J-P
  • Maistre S Le
  • Lellouch E
  • Lunine J I
  • Mandt K E
  • Martins Z
  • Mimoun David
  • Nénon Quentin
  • Caro G M Muñoz
  • Rannou Pascal
  • Rauer H
  • Schmitt-Kopplin P
  • Schneeberger Antoine
  • Simons M
  • Stephan K
  • van Hoolst T.
  • Vaverka J
  • Wieser M
  • Wörner L
  The Planetary Science Journal, IOP Science, 2022, 3, pp.268 (12pp). Enceladus, an icy moon of Saturn, possesses an internal water ocean and jets expelling ocean material into space. Cassini investigations indicated that the subsurface ocean could be a habitable environment having a complex interaction with the rocky core. Further investigation of the composition of the plume formed by the jets is necessary to fully understand the ocean, its potential habitability, and what it tells us about Enceladus's origin. Moonraker has been proposed as an ESA M-class mission designed to orbit Saturn and perform multiple flybys of Enceladus, focusing on traversals of the plume. The proposed Moonraker mission consists of an ESA-provided platform with strong heritage from JUICE and Mars Sample Return and carrying a suite of instruments dedicated to plume and surface analysis. The nominal Moonraker mission has a duration of ∼13.5 yr. It includes a 23-flyby segment with 189 days allocated for the science phase and can be expanded with additional segments if resources allow. The mission concept consists of investigating (i) the habitability conditions of present-day Enceladus and its (10.3847/psj/ac9c03)
  DOI : 10.3847/psj/ac9c03
• Role of avalanche transport in competing drift wave and interchange turbulence
  
  • Ghendrih Philippe
  • Dif-Pradalier Guilhem
  • Panico Olivier
  • Sarazin Yanick
  • Bufferand Hugo
  • Ciraolo Guido
  • Donnel Peter
  • Fedorczak Nicolas
  • Garbet Xavier
  • Grandgirard Virginie
  • Hennequin Pascale
  • Serre Eric
  • Tamain Patrick
  Journal of Physics: Conference Series, IOP Science, 2022, 2397, pp.012018. We complete the 2D 2-fields turbulence model previously used with an interchange-like instability by slightly modifying the parallel loss terms to drive drift wave instabilities. We show that the instability driven by temperature fluctuations of the sheath losses is identical to that of the drift wave turbulence. The linear analysis is performed and used to select control parameters that yield identical maximum growth rates for the interchange alone and drift wave alone instability. Combining the two instabilities doubles the maximum growth rate. The non-linear simulations are used to analyse the SOL width. The simulations allow one to identify a low field side SOL region where interchange and drift wave are unstable and a high field side SOL region where only the drift wave is unstable. The SOL profiles appear exponential in the region close to the source but depart from a simple exponential fall-off in the far SOL. The low field side SOL width is found to be larger in the interchange alone case, slightly smaller when both instabilities are present and finally narrower when only the drift waves. For the high field side SOL, without interchange, the drift wave SOL width is observed to be identical to that on the low field side and larger than that when both instabilities at play. The Sherwood dimensionless parameter, ratio of convective particle flux divided by the diffusive particle flux, is used to compare the efficiency of turbulent transport. The profiles of the Sherwood parameter for time and flux surface averaged transport indicate that turbulent transport is dominant close to the separatrix but is less effective towards the far SOL. The Sherwood parameter evolution, determined with the flux-surface averaged transport, indicates that outward avalanche transport with corrugations governs the case with interchange only. When combining the two instabilities, outward avalanche transport is less pronounced and inward avalanche transport is observed, reducing the overall turbulent transport efficiency. The avalanche transport with drift waves only compared to interchange only is found to be inhibited. (10.1088/1742-6596/2397/1/012018)
  DOI : 10.1088/1742-6596/2397/1/012018
• Cold atmospheric plasma stimulates macrophage killing of bacterial pathogens
  
  • Blaise Océane
  , 2022. Management of thermal burn-injured patients is a challenging field for care units with millions of adults and children concerned worldwide. Important advances over the past decade have occurred in resuscitation, burn wound management or reconstruction. However, patients with severe burns still face disabling consequences such as hypertrophic scars and a high risk of infections and sepsis. Cold atmospheric plasma (CAP) is a partially ionised gas delivering a mixture of reactive oxygen and nitrogen species which favour wound healing and have antimicrobial properties.This PhD study aimed to understand the underlying mechanisms that are responsible for beneficial effects during wound infections specifically on macrophages immune cells. First, we demonstrated in vitro that CAP treatment resulted in a significant decrease in bacterial load for two types of Staphylococcus aureus strains (methicillin-resistant and sensitive: MSSA, MRSA) during their internalization by macrophages. Then, we shown that the enhancement killing of S. aureus by macrophages is mediated by oxidative mechanisms and that CAP promotes phagosome maturation into acidic degradative vesicle. Second, we reported a positive correlation between antibacterial action of CAP and activation of phagocyte NADPH oxidase (NOX2) machinery in two and three-dimensional models of cutaneous infection.In addition, to its antimicrobial effects, CAP is a positive regulator of cutaneous wound healing as shown in an in vivo murine mouse model infected with S. aureus. Finally, the ultimate goal of the project is to treat either uninfected or infected full-thickness burn wounds. Thus, a plasma device has been developed to treat wounds with large surface area. For the first time, this new prototype will be used in porcine model of full-thickness burn wound reconstructed with partial-thickness allografts. This study demonstrated the therapeutic potential of CAP on infected tissue repair. Investigation on tissue repair are promising and further investigations and will be completed by other studies
• Direct observations of energy transfer from resonant electrons to whistler-mode waves in magnetosheath of Earth
  
  • Kitamura N.
  • Amano T.
  • Omura Y.
  • Boardsen S.
  • Gershman D.
  • Miyoshi Y.
  • Kitahara M.
  • Katoh Y.
  • Kojima H.
  • Nakamura S.
  • Shoji M.
  • Saito Y.
  • Yokota S.
  • Giles B.
  • Paterson W.
  • Pollock C.
  • Barrie A.
  • Skeberdis D.
  • Kreisler S.
  • Le Contel O.
  • Russell C.
  • Strangeway R.
  • Lindqvist P.-A.
  • Ergun R.
  • Torbert R.
  • Burch J.
  Nature Communications, Nature Publishing Group, 2022, 13 (1), pp.6259. Abstract Electromagnetic whistler-mode waves in space plasmas play critical roles in collisionless energy transfer between the electrons and the electromagnetic field. Although resonant interactions have been considered as the likely generation process of the waves, observational identification has been extremely difficult due to the short time scale of resonant electron dynamics. Here we show strong nongyrotropy, which rotate with the wave, of cyclotron resonant electrons as direct evidence for the locally ongoing secular energy transfer from the resonant electrons to the whistler-mode waves using ultra-high temporal resolution data obtained by NASA’s Magnetospheric Multiscale (MMS) mission in the magnetosheath. The nongyrotropic electrons carry a resonant current, which is the energy source of the wave as predicted by the nonlinear wave growth theory. This result proves the nonlinear wave growth theory, and furthermore demonstrates that the degree of nongyrotropy, which cannot be predicted even by that nonlinear theory, can be studied by observations. (10.1038/s41467-022-33604-2)
  DOI : 10.1038/s41467-022-33604-2
• Developing high performance RF heating scenarios on the WEST tokamak
  
  • Goniche M.
  • Ostuni V.
  • Bourdelle C.
  • Maget P.
  • Artaud J.F.
  • Bernard J.M.
  • Bobkov V.
  • Bucalossi J.
  • Clairet F.
  • Colas L.
  • Desgranges C.
  • Delpech L.
  • Devynck P.
  • Dumont R.
  • Ekedahl A.
  • Fedorczak N.
  • Garcia J.
  • Gaspar J.
  • Gil C.
  • Guillemaut C.
  • Gunn J.
  • Hillairet J.
  • Klepper C.
  • Lau C.
  • Lerche E.
  • Lombard G.
  • Manas P.
  • Martin E.H.
  • Mazon D.
  • Meyer O.
  • Morales J.
  • Moreau Ph.
  • Nardon E.
  • Nouailletas R.
  • Pegourié B.
  • Peret M.
  • Peysson Y.
  • Regal-Mezin X.
  • Sabot R.
  • Shiraiwa S.
  • Urbanczyk G.
  • Vermare L.
  • Vezinet D.
  • Wallace G.M.
  Nuclear Fusion, IOP Publishing, 2022, 62 (12), pp.126058. Abstract High power experiments, up to 9.2 MW with LHCD and ICRH, have been carried out in the full tungsten tokamak WEST. Quasi non inductive discharges have been achieved allowing to extend the plasma duration to 53 s with stationary conditions in particular with respect to tungsten contamination. Transitions to H mode are observed, and H-modes lasting up to 4 s have been obtained. The increase in stored energy is weak since the power crossing the separatrix is close to the L–H threshold. Hot L mode plasmas (central temperature exceeding 3 keV) with a confinement time following the ITER L96 scaling law are routinely obtained. The weak aspect ratio dependence of this scaling law is confirmed. Tungsten accumulation is generally not an operational issue on WEST. Difficulty of burning through tungsten can prevent the discharge from accessing to a hot core plasma in the ramp-up phase, or can lead to rapid collapse of the central temperature when radiation is enhanced by a slight decrease of the temperature. Except a few pulses post-boronization, the plasma radiation is rather high ( P rad/ P tot ∼ 50%) and is dominated by tungsten. This fraction does not vary as the RF power is ramped up and is quite similar in ICRH and/or LHCD heated plasmas. An estimate of the contribution of the RF antennas to the plasma contamination in tungsten is given. (10.1088/1741-4326/ac9691)
  DOI : 10.1088/1741-4326/ac9691
• Power Anisotropy, Dispersion Signature and Turbulence Diffusion Region in the 3D Wavenumber Domain of Space Plasma Turbulence
  
  • Lin Rong
  • He Jiansen
  • Zhu Xingyu
  • Zhang Lei
  • Duan Die
  • Sahraoui Fouad
  • Verscharen Daniel
  The Astrophysical Journal, American Astronomical Society, 2022, 939 (2), pp.121. Abstract We explore the multifaceted important features of turbulence (e.g., anisotropy, dispersion, and diffusion) in the three-dimensional (3D) wavenumber domain ( k ∥ , k ⊥,1 , k ⊥,2 ), by employing the k-filtering technique to high-quality measurements of fields and particles from the Magnetospheric Multiscale Mission (MMS) multi-spacecraft constellation. We compute the 3D power spectral densities (PSDs) of magnetic and electric field fluctuations (marked as PSD( δ B ( k )) and PSD ( δ E 〈 v i 〉 ′ ( k ) ) , respectively), both of which show a prominent spectral anisotropy in the sub-ion range. We give the first 3D image of the bifurcation between the power spectra of the electric and magnetic fluctuations, by calculating the ratio between PSD ( δ E 〈 v i 〉 ′ ( k ) ) and PSD( δ B ( k )), the distribution of which is related to the nonlinear dispersion relation. We also compute the ratio between electric spectra in different reference frames defined by the ion bulk velocity, PSD ( δ E local v i ′ ) / PSD ( δ E 〈 v i 〉 ′ ) , to visualize the turbulent ion diffusion region (T-IDR) in wavenumber space. The T-IDR has an anisotropy and a preferential direction of wavevectors, which is generally consistent with the plasma wave theory prediction based on the dominance of kinetic Alfvén waves. This work demonstrates the worth of the k-filtering technique in diagnosing turbulence comprehensively, especially when the electric field is involved. (10.3847/1538-4357/ac8e07)
  DOI : 10.3847/1538-4357/ac8e07
• From Cluster to MMS: Analysis of Magnetopause crossings
  
  • Ballerini Giulio
  • Rezeau Laurence
  • Belmont Gérard
  • Califano Francesco
  , 2022.
• Educational project on the design of a demonstrator with automatic pressure measurement
  
  • Zhang Ming
  • Bournel Arnaud
  • Raimbault Jean-Luc
  • Llaser Nicolas
  • Louis Nicolas
  • Malatchoumy Josue
  • Gruat Daniel
  , 2022, pp.1793-1797. In this paper, the design of a demonstrator with automatic pressure measurement is given. This work is proposed as an educational project with the joint contribution of two French teaching institutions and aims at exploiting a Pirani pressure sensor, conventionally used for very low pressure measurement, for beyond atmospheric pressure measurement. The sensor and the associated electronic interface are designed by students majoring in electronics while students majoring in computer science take in charge the software development for the automatic control of the measurement. The hardware implementation of the pressure demonstrator as well as the associated software development is presented in the paper. Within the developed interactive Graphic User Interface (GUI), three data areas are available: pressure related user command, measured pressure and temperature values in real time, and ongoing transient curves acquisition. (10.1109/ISCAS48785.2022.9937821)
  DOI : 10.1109/ISCAS48785.2022.9937821
• PHARE : Parallel hybrid particle-in-cell code with patch-based adaptive mesh refinement
  
  • Aunai Nicolas
  • Smets Roch
  • Ciardi Andrea
  • Deegan Philip
  • Jeandet Alexis
  • Payet Thibault
  • Guyot Nathan
  • Darrieumerlou Loic
  , 2022. Modeling multi-scale collisionless magnetized processes constitutes an important numerical challenge. By treating electrons as a fluid and ions kinetically, the so-called hybrid Particle-In-Cell (PIC) codes represent a promising intermediary between fully kinetic codes, limited to model small scales and short durations, and magnetohydrodynamic codes used large scale. However, simulating processes at scales significantly larger than typical ion particle dynamics while resolving sub-ion dissipative current sheets remain extremely difficult. This paper presents a new hybrid PIC code with patch-based adaptive mesh refinement. Here, hybrid PIC equations are solved on a hierarchy of an arbitrary number of Cartesian meshes of incrementally finer resolution dynamically mapping regions of interest, and with a refined time stepping. This paper presents how the hybrid PIC algorithm is adapted to evolve such mesh hierarchy and the validation of the code on a uniform mesh, fixed refined mesh and dynamically refined mesh.
• Magnetic reconnection in turbulent plasma: Cluster experimental discovery and further developments
  
  • Retino A.
  , 2022.
• What We Still Don't Know About Plasmas in Simple Diatomic Gases- or Using a DC Plasma in Pure O2 as an Ideal Test-Bed for Experimental Validation of Simulations
  
  • Booth Jean-Paul
  , 2022. Despite many decades of study, models of discharges in molecular gases still lack accurate data on many key collisional processes, even for such “simple” and ubiquitous gases as O2. Good data is lacking for near-threshold electron-impact dissociation with neutral products, the role of metastables; of gas heating, vibrational excitation and energy transfer processes; as well as surface recombination and thermal accommodation. Direct measurement of the rate constants of individual processes is a fastidious process, where it is even possible. As an alternative approach, we compare comprehensive measurements of internal plasma parameters to simulations for a plasma with relatively simple chemistry, namely a DC positive column discharge in pure O2. This well-characterized, stable and uniform discharge is optimal for experiment-model comparison. Although this system has been studied for a many decades, new experimental methods, including synchrotron Vacuum ultraviolet absorption spectroscopy and laser cavity ringdown absorption spectroscopy (CRDS), allow the densities of all the major species (atomic, molecular, in ground and excited states) to be measured, with much-improved absolute accuracy, and with time resolution. The gas translational temperature, and vibrational energy distribution, were also probed. Applied to (partially- and fully-) modulated discharges, these measurements provide unprecedented insight into the kinetic processes occurring, and a profound test of the models. Whereas models can be quite easily adjusted to fit steady state measurements at one given set of operating conditions, trends with pressure and discharge current, and especially the temporal response to current modulation, are much harder to reconcile. In practice, model failures can often be attributed to simple omission of key processes, or to the neglect of their temperature-dependence. If the chemistry studied is simple enough, and the measurements cover all of the principal species (stable molecules in their ground and metastable states, atoms and negative ions) as well as the gas temperature, it becomes possible to identify the missing reactions, and even estimate their rates and activation energies, by adjusting their values in the model to fit the observations. As examples, we have demonstrated that the kinetics of metastable O2 b molecules cannot be modelled without the inclusion of quenching by oxygen atoms with a significant activation energy. We have also demonstrated the production of ozone by the reaction of O2 molecules with oxygen atoms chemisorbed on the glass discharge tube walls.
• Etude comparative de sources de plasma froid pour le traitement des cancers des voies biliaires et du poumon
  
  • Soulier Manon
  • Pavy Allan
  • Marmier Solenne
  • Decauchy Henri
  • Lekbaby Bouchra
  • Geraud Korentin
  • Fouassier Laura
  • Cremer Isabelle
  • Dufour Thierry
  , 2022.
• The Helicity Sign of Flux Transfer Event Flux Ropes and Its Relationship to the Guide Field and Hall Physics in Magnetic Reconnection at the Magnetopause
  
  • Dahani S.
  • Kieokaew R.
  • Génot V.
  • Lavraud B.
  • Chen Y.
  • Michotte de Welle B.
  • Aunai N.
  • Tóth G.
  • Cassak P.
  • Fargette N.
  • Fear R.
  • Marchaudon Aurélie
  • Gershman D.
  • Giles B.
  • Torbert R.
  • Burch J.
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2022, 127 (11). Abstract Flux Transfer Events (FTEs) are transient magnetic flux ropes typically found at the Earth's magnetopause on the dayside. While it is known that FTEs are generated by magnetic reconnection, it remains unclear how the details of magnetic reconnection controls their properties. A recent study showed that the helicity sign of FTEs positively correlates with the east‐west ( B y ) component of the Interplanetary Magnetic Field (IMF). With data from the Cluster and Magnetospheric Multiscale missions, we performed a statistical study of 166 quasi force‐free FTEs. We focus on their helicity sign and possible association with upstream solar wind conditions and local magnetic reconnection properties. Using both in situ data and magnetic shear modeling, we find that FTEs whose helicity sign corresponds to the IMF B y are associated with moderate magnetic shears while those that do not correspond to the IMF B y are associated with higher magnetic shears. While uncertainty in IMF propagation to the magnetopause may lead to randomness in the determination of the flux rope core field and helicity, we rather propose that for small IMF B y , which corresponds to high shear and low guide field, the Hall pattern of magnetic reconnection determines the FTE core field and helicity sign. In that context we explain how the temporal sequence of multiple X‐line formation and the reconnection rate are important in determining the flux rope helicity sign. This work highlights a fundamental connection between kinetic processes at work in magnetic reconnection and the macroscale structure of FTEs. (10.1029/2022JA030686)
  DOI : 10.1029/2022JA030686
• Foundations of plasma surface functionalization of polymers for industrial and biological applications
  
  • Booth Jean-Paul
  • Mozetič Miran
  • Nikiforov Anton
  • Oehr Christian
  Plasma Sources Science and Technology, IOP Publishing, 2022, 31 (10), pp.103001. Abstract Polymer materials are widely employed in many fields due to the ease with which they can be formed into complex shapes, their versatile mechanical properties, light weight, and low cost. However, many applications are hindered by the chemical compatibility of polymer surfaces, which are generally hydrophobic and bond poorly to other media such as paints, glues, metals and biological media. While polymer surfaces can be treated by wet chemical processes, the aggressive reagents employed are detrimental to the environment, limiting the range of modifications that can be achieved by this route. Plasma functionalization is an attractive alternative, offering great versatility in the processed surface characteristics, and generally using environmentally benign compounds such as rare gases, oxygen and nitrogen, as well as very small quantities of organic precursors. Since the modified surfaces are only a few monolayers thick, these processes are extremely rapid and low in cost. The first industrial process to be developed was plasma oxidation, which increases the surface energy of the polymer, improving the adhesion of paint, glue and metal to the component. Plasma oxidation can be achieved using both low-pressure and atmospheric pressure (APP) discharges. Subsequently, many other processes have emerged, allowing other functional groups to be grafted, including amines, hydroxyl and carboxylic acid groups. Plasma polymerization, starting from gaseous monomers, allows a whole new family of surface chemistries to be created. These processes have many exciting applications in the biomedical field due to the control they give on biocompatibility and selective interaction with living cells. This article will present the fundamentals of plasma interactions with polymers, the plasma devices employed (both at low-pressure and at APP) with their advantages and drawbacks, and a survey of current and future applications. (10.1088/1361-6595/ac70f9)
  DOI : 10.1088/1361-6595/ac70f9
• Observation and Modeling of the Solar Wind Turbulence Evolution in the Sub-Mercury Inner Heliosphere
  
  • Telloni Daniele
  • Adhikari Laxman
  • Zank Gary
  • Hadid L. Z.
  • Sánchez-Cano Beatriz
  • Sorriso-Valvo Luca
  • Zhao Lingling
  • Panasenco Olga
  • Shi Chen
  • Velli Marco
  • Susino Roberto
  • Verscharen Daniel
  • Milillo Anna
  • Alberti Tommaso
  • Narita Yasuhito
  • Verdini Andrea
  • Grimani Catia
  • Bruno Roberto
  • D’amicis Raffaella
  • Perrone Denise
  • Marino Raffaele
  • Carbone Francesco
  • Califano Francesco
  • Malara Francesco
  • Stawarz Julia
  • Laker Ronan
  • Liberatore Alessandro
  • Bale Stuart
  • Kasper Justin
  • Heyner Daniel
  • de Wit Thierry Dudok
  • Goetz Keith
  • Harvey Peter
  • Macdowall Robert
  • Malaspina David
  • Pulupa Marc
  • Case Anthony
  • Korreck Kelly
  • Larson Davin
  • Livi Roberto
  • Stevens Michael
  • Whittlesey Phyllis
  • Auster Hans-Ulrich
  • Richter Ingo
  The Astrophysical Journal Letters, Bristol : IOP Publishing, 2022, 938 (2), pp.L8. Abstract This letter exploits the radial alignment between the Parker Solar Probe and BepiColombo in late 2022 February, when both spacecraft were within Mercury’s orbit. This allows the study of the turbulent evolution, namely, the change in spectral and intermittency properties, of the same plasma parcel during its expansion from 0.11 to 0.33 au, a still unexplored region. The observational analysis of the solar wind turbulent features at the two different evolution stages is complemented by a theoretical description based on the turbulence transport model equations for nearly incompressible magnetohydrodynamics. The results provide strong evidence that the solar wind turbulence already undergoes significant evolution at distances less than 0.3 au from the Sun, which can be satisfactorily explained as due to evolving slab fluctuations. This work represents a step forward in understanding the processes that control the transition from weak to strong turbulence in the solar wind and in properly modeling the heliosphere. (10.3847/2041-8213/ac9624)
  DOI : 10.3847/2041-8213/ac9624