Publications

2025

• Investigation of filamentary and diffuse DBD in CO 2 by means of in-situ FTIR absorption spectroscopy
  
  • Bajon Corentin
  • Baratte Edmond
  • Sadi Dihya
  • Guaitella Olivier
  • Belinger Antoine
  • Dap Simon
  • Hoder Tomas
  • Naudé Nicolas
  , 2025. This work investigates CO2 dielectric barrier discharges at atmospheric pressure in the filamentary and diffuse regimes for the first time using in situ FTIR absorption measurements. The conversion factor of CO2 is determined and is consistent with the results obtained for DBDs in the literature. Vibrational temperatures for CO2 and CO molecules are also determined, as well as the rotational temperature. The ordering of the different temperatures is similar to the reported results for other CO2 discharges. The evolution of the measured parameters as a function of the specific energy input is discussed and a comparison of the two different regimes is carried out.
• Rapport de conjoncture de la Section 17 "SYSTÈME SOLAIRE ET UNIVERS LOINTAIN" du Comité National de la Recherche Scientifique - Mandature 2021-2025
  
  • Motte Frederique
  • Famaey Benoit
  • Lamy Laurent
  • Aghanim Nabila
  • Baklouti Donia
  • Bournaud Frédéric
  • Cambrésy L.
  • Codis Sandrine
  • Issautier Karine
  • Leconte Jérémy
  • Mirioni Laurent
  • N'Diaye Mamadou
  • Oertel Micaela
  • Palacios Ana
  • Recio-Blanco Alejandra
  • Roy Fabrice
  • Theureau Gilles
  • Savalle Renaud
  • Tibaldo Luigi
  • Tresse Laurence
  • Vincent F
  • Caffau Elisabetta
  • Douet Richard
  • Laibe Guillaume
  • Regimbau Tania
  • Reylé Céline
  , 2025. Ce rapport s'adresse à un lectorat non expert de la discipline Astrophysique, souhaitant avoir un aperçu de l'évolution de notre communauté de recherche au sein de CNRS INSU (Institut National des Sciences de l'Univers, également appelé CNRS Terre & Univers) sur la période 2022-2024. Il présente un résumé thématique et méthodologique de nos activités, un panorama de la structuration actuelle de notre communauté, ainsi qu'un bilan des recrutements et des promotions. Il est fondé sur le travail de la section 17, lequel comprend les concours de recrutement, les recrutements contractuels RQTH, la carrière (évaluation, promotion, éméritat, demande de rattachement à la section ou de détachement de celle-ci, changement d'affectation et RIPEC C3) des personnels de recherche rattachés à la section 17 ; l'évaluation des structures rattachées à la section 17 ; les propositions pour les médailles d'argent et de bronze du CNRS ; les demandes d'accueil en délégation au CNRS ; les écoles thématiques.
• Quantitative estimates of the magnetic flux variations in the inner magnetosphere during an intense storm.
  
  • Alqeeq Soboh
  • Fontaine Dominique
  • Le Contel Olivier
  • Akhavan-Tafti Mojtaba
  • Cazzola Emanuele
  • Atilaw Tsige
  , 2025. In the present study, we analyzed the Earth's magnetospheric dynamics in response to the intense geomagnetic storm of 19th December 2015, marked by a substantial decrease in the SYM-H index to -188 nT. We focushere on the variations of the magnetic flux content (MFC) within closed magnetic shells in the inner magnetosphe up to a distance roughly corresponding to the magnetopause. During this event, we had the chance to have observations on the dayside and on the nightside and at different distances in the magnetosphere (OMNI, Van Allen Probes, GOES, THEMIS, MMS, Cluster). Using these various observations together with the Tsyganenko T96 model, we estimated the MFC in the inner magnetosphere. It is found that in comparison to pre-storm conditions, MCF decreased during SSC by 17% and in the main phase by 27% but it gradually rebounded (swelled) during 3 following days of the recovery phase reducing the decrease to 22%, 14% and 8% respectively. The importance of storm-time magnetospheric dynamics in the field of space weather forecasting is emphasized by these findings and calls for further studies. (10.5194/egusphere-egu25-8724)
  DOI : 10.5194/egusphere-egu25-8724
• The SCM instrument for the ESA Plasma Observatory mission
  
  • Le Contel Olivier
  • Kretzschmar Matthieu
  • Retino Alessandro
  • Mehrez Fatima
  • Jannet Guillaume
  • Alison Dominique
  • Revillet Claire
  • Mirioni Laurent
  • Agrapart Clémence
  • Sou Gérard
  • Geyskens Nicolas
  • Berthod Christophe
  • Chust Thomas
  • Berthomier Matthieu
  • Fiachetti Cécile
  • Khotyaintsev Yuri
  • Cripps Vicki
  • Marcucci Maria Federica
  , 2025. The proposal of the Plasma Observatory mission was selected for a competitive phase A with two other missions in the framework of the seventh call for medium mission (M7) organized by ESA. The mission selection is planned in 2026 for a launch in 2037. Its main objectives are to unveil how are particles energized in space plasma and which processes dominate energy transport and drive coupling between the different regions of the terrestrial magnetospheric system? The mission consists of seven satellites, a main platform (mothercraft, MSC) and six smaller identical satellites (daughtercraft) evolving along an equatorial elliptical orbit with an apogee ~17 and a perigee ~8 Earth radii. The seven satellites will fly forming two tetraedra and allowing simultaneous measurements at both fluid and ion scales. The mission will include three key science regions: dayside (solar wind, bow shock, magnetosheath, magnetopause), nightside transition region (quasidipolar region, transient near-Earth current sheet, field-aligned currents, braking flow region) and the medium magnetotail (near-Earth reconnection region, fast flow formation region). Plasma Observatory mission is the next logical step after the four satellite magnetospheric missions Cluster and MMS. The search-coil magnetometer (SCM), strongly inherited of the SCM designed for the ESA JUICE mission, is only included in the Fields instrument suite of the MSC. SCM will be delivered by LPP and LPC2E and will provide the three components of the magnetic field fluctuations in the [0.1Hz-8kHz] frequency range, after digitization by the Low frequency Receiver (LFR) within the Field and Wave Processor (FWP), relevant for the three Key science regions. It will be mounted on a 6m boom and will allow to reach the following sensitivities [10-3, 1.5x10-6, 5x10-9, 10-10, 5x10-10] nT2/Hz at [1, 10, 100, 1000, 8000] Hz. Associated with the electric field instrument (EFI), SCM will allow to fully characterize the wave polarization and estimate the direction of propagation of the wave energy. These measurements are crucial to understand the role of electromagnetic waves in the energy conversion processes, the plasma and energy transport, the acceleration and the heating of the plasma. (10.5194/egusphere-egu25-16777)
  DOI : 10.5194/egusphere-egu25-16777
• Particle-In-Cell simulations of an electron beam: stability and wave emissions
  
  • Dargent Jeremy
  • Ripoll Jean-François
  • Beck Arnaud
  • Le Contel Olivier
  • Retinó Alessandro
  , 2025. During peaks of magnetospheric activity, energetic electrons trapped in the inner magnetosphere can precipitate in the lower ionosphere due to electromagnetic wave activity. Such waves can be generated naturally or artificially, for instance, through the emission of plasma beams. In this work, we study waves generated by electron beams emitted parallel to the magnetic field using fully kinetic Particle-In-Cell simulations. To this end, we use the heavily parallelized SMILEI code. To reduce the weight of the simulation, we take advantage of the rotational symmetry of the problem and use a cylindrical frame, which reduces the simulation to a 2D problem with cylindrical symmetry. We investigate the impact of the beam characteristics (such as beam density, frequency, length, etc.) on the wave generation, and the structural evolution of the beam as it exchanges energy with the electromagnetic fields and interacts with the background plasma. (10.5194/egusphere-egu25-10538)
  DOI : 10.5194/egusphere-egu25-10538
• 2D fully kinetic simulations of dayside magnetic reconnection in the presence of cold ions and a moderate guide field.
  
  • Baraka Mohammed
  • Le Contel Olivier
  • Retino Alessandro
  • Dargent Jérémy
  • Beck Arnaud
  • Toledo-Redondo Sergio
  • Cozzani Giulia
  • Fuselier Stephen
  • Chust Thomas
  • Alqeeq Soboh
  , 2025. The standard conditions considered for magnetic reconnection to occur are usually antiparallel magnetic field configurations with a shear angle of 180◦. Reconnection is often observed with an additional out-of-plane component of the magnetic field (guide field). We performed two sets of 2D fully kinetic simulations using SMILEI code of asymmetric reconnection. The first set was performed initially by Dargent et al., 2017 with and without cold ions. While the second set with and without cold ions each conducted in the presence of a moderate guide field. The simulation domain size is set to (xmax , ymax) = (320, 128) di, enabling us to study these effects in the electron diffusion region (EDR) as well as the coupling across different scales, including ion diffusion region (IDR), outflow jets, and extended separatrices far from diffusion region. When the density gradient is combined with a guide field component at the magnetopause, it was suggested by Swisdak et al., 2003 that the electron diamagnetic drift governs the motion of the X-line.Our simulations reveal the development of an asymmetry in the reconnection plane as expected and a motion of the X-line in the opposite direction of the electron diamagnetic drift. This finding challenges the previously proposed explanation. We also report our progress in investigating the impact of cold ions in reinforcing the electron dynamics and further investigate the impact of adding a moderate guide field in their presence. These effects are expected to influence the energization, energy partitioning across scales, and potentially the suppression of reconnection. Fluid scales coupling with smaller ion scales aligns with the primary objective of the Plasma Observatory (PO) mission which aims to study plasma energization and energy transport. Our findings will contribute to the preparation of the PO mission and aim at improving its science return. (10.5194/egusphere-egu25-18438)
  DOI : 10.5194/egusphere-egu25-18438
• An Electron Plasma Camera for the Plasma Observatory ESA mission
  
  • Berthomier Matthieu
  • Forsyth Colin
  • Leblanc Frédéric
  • Techer Jean-Denis
  • Alata Yvon
  • Poggia Gabriel
  • Seneret Evan
  • Brockley-Blatt Chris
  • Retino Alessandro
  • Le Contel Olivier
  , 2025. Measuring both the energy spectrum and the 3D distribution of charged particles at high temporal resolution is one of the main challenges in space plasma instrumentation. The conventional solution to date has been to use multiple sensors that couple the native quasi-2D instantaneous field of view of the electrostatic top-hat analyser with a scanning electrostatic deflection system.For the Plasma Observatory ESA mission, we proposed an alternate strategy that reduces the level of resources required for rapid plasma measurements at sub-ion scale in the magnetospheric environment. The Electron Plasma Camera (EPC) is based on the donut-shaped electrostatic analyser topology that do not require any electrostatic scanning to provide a hemispheric field-of-view of the surrounding plasma.This optics is manufactured through the selective metallization of a high-resolution 3D printed polymer. It is coupled to a 256-pixel imaging detection system that uses the detection technology that was demonstrated on the Solar Orbiter mission. EPC’s fully integrated front-end electronics takes advantage of the high-geometric factor of its electrostatic optics to enable the capture of high temporal resolution images of electron phase space. We present the expected capability of the instrument in the key science regions the Plasma Observatory mission will encounter, and some of the major science questions related to multi-scale phenomena the Plasma Observatory mission will address with its unique data set. (10.5194/egusphere-egu25-17978)
  DOI : 10.5194/egusphere-egu25-17978
• The Search-Coil Magnetometer (SCM) of the Radio and Plasma Waves Investigation (RPWI) onboard the ESA JUICE mission: in-flight performance and first observations.
  
  • Retino Alessandro
  • Mansour Malik
  • Le Contel Olivier
  • Chust Thomas
  • Stassen Theo
  • Mirioni Laurent
  • Piberne Rodrigue
  • Santolik Ondrej
  • Soucek Jan
  • Pisa David
  • Wahlund Jan-Erik
  • Khotyaintsev Yuri
  • Bergman Jan
  , 2025. The JUpiter ICy moons Explorer (JUICE) mission is the first large-class (L1) mission of ESA Cosmic Vision. JUICE has been launched in April 2023 with an arrival at Jupiter in 2031 and at least four years making detailed plasma observations of Jupiter's magnetosphere and of three of its largest moons (Ganymede, Callisto and Europa). The Radio and Plasma Wave Investigation (RPWI) consortium will carry the most advanced set of electric and magnetic fields sensors ever flown in Jupiter's magnetosphere, which will allow to characterize the radio emission and plasma wave environment of Jupiter and its icy moons. The Search Coil Magnetometer (SCM) of RPWI, combined with the RPWI Low-Frequency receiver (LF), will provide for the first time three-dimensional measurements of magnetic field fluctuations within Jupiter's magnetosphere, with high sensitivity (~10 fT / √Hz at 1 kHz) in the frequency range 0.1 Hz - 20 kHz. Here we present SCM in-flight performance and first observations obtained during its cruise phase, including those from the Lunar-Earth Gravity Assist (LEGA) in 2024. These observations show a nominal functioning and performance of SCM, in agreement with ground calibrations, together with a rather good magnetic cleanliness of the JUICE spacecraft. Observations during LEGA have also allowed to properly identify a number of plasma boundaries in the Earth’s magnetosphere, such as the magnetopause and the magnetotail current sheet, successfully testing the SCM capability to study such boundaries at Jupiter’s and of Ganymede's magnetosphere. (10.5194/egusphere-egu25-20614)
  DOI : 10.5194/egusphere-egu25-20614
• MMS Analysis of a Dayside Compressed Magnetospheric Separatrix in the Presence of Cold Ions and a Moderate Guide Field
  
  • Baraka M.
  • Le Contel O.
  • Canu P.
  • Alqeeq S W
  • Dargent J.
  • Beck A.
  • Cozzani G.
  • Retinò A.
  • Chust T.
  • Mirioni L.
  • Toledo‐redondo S
  • Akhavan‐tafti M
  • Bandyopadhyay R.
  • Chasapis A.
  • Norgren C.
  • Khotyaintsev Y.
  • Ahmadi N.
  • Wei H Y
  • Fischer D.
  • Gershman D J
  • Burch J L
  • Torbert R B
  • Giles B L
  • Fuselier S A
  • Ergun R E
  • Lindqvist P.-A ‐a
  • Russell C T
  • Strangeway R J
  • Bromund K R
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2025, 130 (4). This study reports on a dayside magnetic reconnection event detected by the Magnetospheric Multiscale mission in the presence of a moderate guide field (times the reconnecting magnetic field on the magnetosphere side) and assumed to be present in the whole reconnection region. The spacecraft traversed the compressed magnetospheric separatrix region, observing cold ions with densities up to 10 cm-3 and a large magnetosheath density of up to 150 cm-3. We provide a detailed analysis of current densities, generalized Ohm's law, and energy conversion processes in both the spacecraft and the fluid frames during the separatrix crossing. The normal electric field is directed away from the separatrix due to the cold ion drift on the magnetosphere side and to the magnetosheath ion drift in the presence of a guide field in the exhaust region. In the spacecraft frame, energy transfers from the plasma to the fields due to the convective field associated with the earthward motion of the magnetopause and the ion diamagnetic current associated with the large density gradient. In the fluid frame, energy conversion reverses due to the magnetic field-aligned current density and electric field produced by the divergence of the electron pressure tensor. Additionally, we give insights into the local changes in electromagnetic, bulk flow, and thermal energies. We show that flow and thermal energy variations of the plasma are mostly driven by the compressible term of the electron pressure strain at the separatrix. (10.1029/2024JA033234)
  DOI : 10.1029/2024JA033234
• Transferred plasma catheter for endotherapeutic applications: a parametric study of guided streamers dynamics
  
  • Soulier Manon
  • Vacek Thibaut
  • Géraud Korentin
  • Dufour Thierry
  Physics of Plasmas, American Institute of Physics, 2025, 32 (4). Non-thermal atmospheric pressure plasma jets (APPJs) are increasingly used in biomedical applications due to their low temperatures and ability to generate reactive oxygen and nitrogen species (RONS), making them suitable for sensitive environments like medical therapies. The transferred plasma catheter (TPC), a variant of APPJ, shows promise for endoscopic applications but requires precise control of plasma dynamics in confined spaces to ensure safety and efficacy. Despite extensive studies on guided streamers in traditional APPJs, there is limited understanding of streamer behavior in TPC configurations, particularly in challenging scenarios involving grounded metallic surfaces. This study examines the spatiotemporal dynamics of guided streamers generated by TPCs under varying gap distances to establish a robust framework for safe and effective plasma delivery in endoscopic settings. Combining electrical and optical diagnostics, the study characterizes streamer propagation, electric field profiles, and plasma-induced currents in a helium-driven TPC delivering cold plasma to a grounded metal target across gaps of 2 to 18 mm. Results show that streamers maintain charge stability and effectively interact with the target for gap distances below 12 mm, producing significant therapeutic currents. Beyond this threshold, propagation deteriorates due to recombination and reduced electric field intensity. For shorter gaps, counterpropagating waves and secondary streamer interactions are observed, while larger gaps lead to charge dissipation and reduced efficacy. These findings highlight the importance of optimizing gap distances for plasma-assisted endoscopic procedures and demonstrate the TPC's robustness in adverse conditions. (10.1063/5.0254402)
  DOI : 10.1063/5.0254402
• MESSENGER Observations of a Possible Alfvén Wing at Mercury Driven by a Low Alfvénic Mach Number Interplanetary Coronal Mass Ejection
  
  • Bowers Charles
  • Jackman Caitríona
  • Jia Xianzhe
  • Slavin James
  • Saur Joachim
  • Holmberg Mika
  • Dewey Ryan
  • Heyner Daniel
  • Elekes Filip
  • Hadid Lina
  • Lavraud Benoit
  • Wang Yang
  • Huybrighs Hans
  • Rutala Matthew
  • Fogg Alexandra
  • Lee Stephenie Brophy
  • Hollman Daragh
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2025, 130 (3). Abstract We investigate Mercury's response to rare, low Alfvénic Mach number solar wind conditions using observations from the Mercury Surface, Space Environment, Geochemistry, and Ranging (MESSENGER) mission. This study provides compelling evidence of Mercury's altered magnetospheric state under these extreme conditions, including the first observational confirmation of Alfvén wing formation at the planet. Our analysis estimates that the upstream conditions during the interplanetary coronal mass ejection (ICME) were sub‐to trans‐Alfvénic ( 1.5). These unusually low solar wind conditions were driven by large interplanetary magnetic fields (IMF) associated with an ICME impact observed by MESSENGER on 30 December 2011. During this 17 hr event, MESSENGER completed one orbital pass through Mercury's magnetosphere, capturing magnetic field and plasma observations of its altered state. We compare these observations to a three‐dimensional magnetohydrodynamic simulation of the event and to MESSENGER observations under typical conditions ( 5.0). Compared with its nominal state, the dayside magnetosphere during the ICME exhibited a weaker, more expanded bow shock and significantly lower plasma density within the magnetosheath. On the nightside, MESSENGER observed a highly inclined magnetic field relative to the typical magnetospheric magnetic field, populated with high‐density plasma consistent with the formation of an Alfvén wing– a characteristic feature of sub‐Alfvénic magnetospheric interactions. This investigation of Mercury under extreme conditions provides insights into the nominal, sub‐Alfvénic interactions between many outer planet moons and their host planet's magnetosphere and also informs our understanding of the many exoplanetary‐stellar wind interactions occurring in low‐ environments. (10.1029/2024JA033619)
  DOI : 10.1029/2024JA033619
• Decay of Turbulent Upper-hybrid Waves in Weakly Magnetized Solar Wind Plasmas
  
  • Polanco-Rodríguez F.
  • Krafft C.
  • Savoini P.
  The Astrophysical Journal Letters, Bristol : IOP Publishing, 2025, 982 (1), pp.L24. Large-scale and long-term two-dimensional particle-in-cell simulations of high resolution are performed for the first time to study the dynamics of electrostatic decay of upper-hybrid wave turbulence generated by electron beams into Langmuir/$\mathcal{Z}$-mode ($\mathcal{LZ}$) waves in weakly to moderately magnetized plasmas, in conditions relevant to type III solar radio bursts. Simulations use parameters characteristic of beam–plasma interactions between ∼0.1 and 1 au. The impact of plasma magnetic field on decay is shown, and magnetic properties of $\mathcal{LZ}$ waves are determined. During their energy transport through k wavevector scales, waves undergo several decay cascades, acquiring increasing magnetic energy until they reach electromagnetic $\mathcal{Z}$-mode dispersion below the plasma frequency. Whereas the impact of magnetic field on decaying waves of large k = ∣ k ∣ is weak, important differences with respect to the unmagnetized plasma case manifest at small k -scales, where a boundary layer delimiting a spectral domain free of $\mathcal{LZ}$ energy is revealed. It prevents decayed waves from reaching the $\mathcal{Z}$-mode cutoff frequency and a high level of left-handed polarization, and it modifies the conditions for the appearance of modulational instabilities and strong turbulence phenomena at k ∼ 0. Ordinary $\mathcal{O}$-mode waves are generated jointly with $\mathcal{Z}$-mode waves at comparable energy levels, via electromagnetic decay, whereas $\mathcal{X}$-mode emissions are much weaker in most cases. These results provide support for the interpretation of observations by satellites such as Parker Solar Probe and Solar Orbiter, and they supply a solid basis for tackling the more complex problem of dynamics of upper-hybrid wave turbulence in magnetized plasmas where random density fluctuations cannot be neglected. (10.3847/2041-8213/adba64)
  DOI : 10.3847/2041-8213/adba64
• Milestone in predicting core plasma turbulence: successful multi-channel validation of the gyrokinetic code GENE
  
  • Höfler Klara
  • Görler Tobias
  • Happel Tim
  • Lechte Carsten
  • Molina Pedro
  • Bergmann Michael
  • Bielajew Rachel
  • Conway Garrard
  • David Pierre
  • Denk Severin
  • Fischer Rainer
  • Hennequin Pascale
  • Jenko Frank
  • Mcdermott Rachael
  • White Anne
  • Stroth Ulrich
  Nature Communications, Nature Publishing Group, 2025, 16 (1), pp.2558. Abstract On the basis of several recent breakthroughs in fusion research, many activities have been launched around the world to develop fusion power plants on the fastest possible time scale. In this context, high-fidelity simulations of the plasma behavior on large supercomputers provide one of the main pathways to accelerating progress by guiding crucial design decisions. When it comes to determining the energy confinement time of a magnetic confinement fusion device, which is a key quantity of interest, gyrokinetic turbulence simulations are considered the approach of choice – but the question, whether they are really able to reliably predict the plasma behavior is still open. The present study addresses this important issue by means of careful comparisons between state-of-the-art gyrokinetic turbulence simulations with the GENE code and experimental observations in the ASDEX Upgrade tokamak for an unprecedented number of simultaneous plasma observables. (10.1038/s41467-025-56997-2)
  DOI : 10.1038/s41467-025-56997-2
• Magnetosphere and Plasma Science with the Jupiter Icy Moons Explorer
  
  • Masters Adam
  • Modolo Ronan
  • Roussos Elias
  • Krupp Norbert
  • Witasse Olivier
  • Vallat Claire
  • Cecconi Baptiste
  • Edberg Niklas J T
  • Futaana Yoshifumi
  • Galand Marina
  • Heyner Daniel
  • Holmberg Mika
  • Huybrighs Hans
  • Jia Xianzhe
  • Khurana Krishan
  • Lamy Laurent
  • Roth Lorenz
  • Sulaiman Ali
  • Tortora Paolo
  • Barabash Stas
  • Bruzzone Lorenzo
  • Dougherty Michele K
  • Gladstone Randall
  • Gurvits Leonid I
  • Hartogh Paul
  • Hussmann Hauke
  • Iess Luciano
  • Poulet François
  • Wahlund Jan-Erik
  • Andrews David J
  • Arridge Chris S
  • Bagenal Fran
  • Baskevitch Claire
  • Bergman Jan
  • Bocanegra Tatiana M
  • Brandt Pontus
  • Bunce Emma J
  • Clark George
  • Coates Andrew J
  • Galanti Eli
  • Galli André
  • Grodent Denis
  • Jones Geraint
  • Kasaba Yasumasa
  • Kaspi Yohai
  • Katoh Yuto
  • Kaweeyanun Nawapat
  • Khotyaintsev Yuri
  • Kimura Tomoki
  • Kollmann Peter
  • Mitchell Don
  • Moirano Alessandro
  • Molera Calvés Guifré
  • Morooka Michiko
  • Müller-Wodarg Ingo C F
  • Muñoz Claudio
  • Mura Alessandro
  • Pätzold Martin
  • Pinto Marco
  • Plainaki Christina
  • Retherford Kurt D
  • Retinò Alessandro
  • Rothkaehl Hanna
  • Santolík Ondřej
  • Saur Joachim
  • Stenberg Wieser Gabriella
  • Tsuchiya Fuminori
  • Volwerk Martin
  • Vorburger Audrey
  • Wurz Peter
  • Zannoni Marco
  Space Science Reviews, Springer Verlag, 2025, 221, pp.art. 24. The Jupiter Icy Moons Explorer ( JUICE ) is a European Space Agency mission to explore Jupiter and its three icy Galilean moons: Europa, Ganymede, and Callisto. Numerous JUICE investigations concern the magnetised space environments containing low-density populations of charged particles that surround each of these bodies. In the case of both Jupiter and Ganymede, the magnetic field generated internally produces a surrounding volume of space known as a magnetosphere. All these regions are natural laboratories where we can test and further our understanding of how such systems work, and improved knowledge of the environments around the moons of interest is important for probing sub-surface oceans that may be habitable. Here we review the magnetosphere and plasma science that will be enabled by JUICE from arrival at Jupiter in July 2031. We focus on the specific topics where the mission will push forward the boundaries of our understanding through a combination of the spacecraft trajectory through the system and the measurements that will be made by its suite of scientific instruments. Advances during the initial orbits around Jupiter will include construction of a comprehensive picture of the poorly understood region of Jupiter’s magnetosphere where rigid plasma rotation with the planet breaks down, and new perspectives on how Jupiter’s magnetosphere interacts with both Europa and Callisto. The later orbits around Ganymede will dramatically improve knowledge of this moon’s smaller magnetosphere embedded within the larger magnetosphere of Jupiter. We conclude by outlining the high-level operational strategy that will support this broad science return. (10.1007/s11214-025-01148-8)
  DOI : 10.1007/s11214-025-01148-8
• Shell models on recurrent sequences: Fibonacci, Padovan, and other series
  
  • Manfredini Lorenzo
  • Gürcan Özgür D.
  Physical Review E, American Physical Society (APS), 2025, 111 (2), pp.025103. A new class of shell models is proposed, where the shell variables are defined on a recurrent sequence of integer wave-numbers such as the Fibonacci or the Padovan series, or their variations including a sequence made of square roots of Fibonacci numbers rounded to the nearest integer. Considering the simplest model, which involves only local interactions, the interaction coefficients can be generalized in such a way that the inviscid invariants, such as energy and helicity, can be conserved even though there is no exact self-similarity. It is shown that these models basically have identical features with standard shell models, and produce the same power law spectra, similar spectral fluxes and analogous deviation from self-similar scaling of the structure functions implying comparable levels of turbulent intermittency. Such a formulation potentially opens up the possibility of using shell models, or their generalizations along with discretized regular grids, such as those found in direct numerical simulations, either as diagnostic tools, or subgrid models. It also allows to develop models where the wave-number shells can be interpreted as sparsely decimated sets of wave-numbers over an initially regular grid. In addition to conventional shell models with local interactions that result in forward cascade, a particular helical shell model with long range interactions is considered on a similarly recurrent sequence of wave numbers, corresponding to the Fibonacci series, and found to result in the usual inverse cascade. (10.1103/PhysRevE.111.025103)
  DOI : 10.1103/PhysRevE.111.025103
• Asymmetric dual cascade in gravitational wave turbulence
  
  • Gay Benoît
  • Galtier Sébastien
  , 2025. We numerically simulate, in both the forced and decay regimes, a fourth-order nonlinear diffusion equation derived from the kinetic equation of gravitational wave turbulence in the limit of strongly local quartic interactions. When a forcing is applied to an intermediate wavenumber $k_i$, we observe a dual cascade of energy and wave action. In the stationary state, the associated flux ratio is proportional to $k_i$, and the Kolmogorov-Zakharov spectra are recovered. In decaying turbulence, the study reveals that the wave action spectrum can extend to wavenumbers greater than the initial excitation $k_i$ with constant negative flux, while the energy flux is positive with a power law dependence in $k$. This leads to an unexpected result: a single inertial range with a Kolmogorov-Zakharov wave action spectrum extending progressively to wavenumbers larger than $k_i$. We also observe a wave action decay in time in $t^{-1/3}$ while the front of the energy spectrum progresses according to a $t^{1/3}$ law. These properties can be understood with simple theoretical arguments.
• Study of Dayside Magnetic Reconnection in the Presence of Cold Ions and Guide Field : A Focus on the Magnetospheric Separatrix
  
  • Baraka Mohammed
  , 2025. Depending on the orientation of the interplanetary magnetic field (IMF) transported by the solar wind, the magnetic field lines of the Earth's magnetic field can reconnect with those of the IMF at the dayside magnetopause, the boundary between the solar wind and the Earth's magnetic field. As the plasma conditions on each side of the magnetopause are different, the magnetic reconnection is called asymmetric. The reconnection process starts in a diffusion region at electron scales and generates fast diverging electron and ion jets. The boundaries separating the plasma flowing into the reconnection region from the outflow plasma are called the separatrices. This PhD thesis investigates in detail the structure of the magnetospheric separatrix far from the diffusion region in the presence of magnetospheric cold ions, a high density gradient and a moderate guide field. Using in-situ measurements of the NASA Magnetospheric Multiscale(MMS) mission and fully kinetic 2D Particle-In-Cell (PIC) simulations obtained from the open source SMILEI code, the current densities, electric and magnetic signatures as well as energy conversion processes are investigated. From in-situ measurements at the separatrix, the current density is found dominated by the ion diamagnetic current and the normal electric field sustained by the drift of the cold ions in agreement with the simulations. The energy conversion in the fluid frame is ensured by the parallel current and the electric field produced by the parallel electron pressure term. The partitioning of the energy between ions and electrons is discussed based on the pressure strain calculations. From the kinetic simulations performed with and without cold ions, and with and without guide field, it is found that with a guide field, the presence of cold ions reinforces the electron pressure gradient reducing the normal electric field and increasing the motion of the reconnection region. All these effects modify the energy and plasma exchanges between the solar wind and the Earth's magnetosphere.
• Numerical model of the PEGASES spacecraft thruster
  
  • Lequette Nicolas
  , 2025. The electric spacecraft propulsion industry is actively transitioning to new propellants.Until recently, the favoured propellant was xenon. It is the heaviest stable noble gas, characteristics that enhance the thrust-to-power ratio of electric thrusters. However, the limited supply cannot satisfy the growing demand as space industrializes.New propulsion systems are designed around lighter noble gases, trading efficiency for affordability.Others make use of molecular propellants, namely iodine. Despite being reactive, this element, a neighbour of xenon in the periodic table, can offer similar performances with the benefit of a higher storage density.The development of the next propulsion systems requires design and simulation tools adapted to alternative propellants. In this work, we propose using a 1D Particle-In-Cell code coupled with a fluid model as a fast way to simulate the low-pressure discharges found in electric thrusters.We implemented an analytical model to emulate the particle transport in the unsimulated directions.This method allows the simulation of simple geometries with a 1D model. In addition, the vacuum permittivity scaling technique allows to speed up whole device simulations.To ensure the accuracy of our model, we extensively validated it using the diagnostic data measured on the PEGASES thruster. This validation process covered a range of noble gases and iodine ICP discharges, including argon, krypton, xenon.Noble gas validation showed that the code could reproduce the trends in the electron parameters as the pressure and power evolved. However, its reduced dimensionality and the fluid model hinder its predictive power at low pressure and high power. In iodine, the low-pressure simulations are in good agreement with the experimental data. However, the model struggles to maintain the delicate balance between the numerous species at high pressure.
• Ionospheric Plasma Irregularities During Intense geomagnetic storms of Solar Cycle 25
  
  • Imtiaz Nadia
  • Calabia Andres
  • Anoruo Chukwuma
  • Zahid Aqsa
  • Amory Christine
  • Adhikari Binod
  Annales Geophysicae, European Geosciences Union, 2025. Abstract. This study aims to characterize several key aspects of the ionosphere during intense geomagnetic storms that occurred on March 23–25, 2023, April 23–25, 2023, November 4–7, 2023 and May 10–13, 2024 during the ascending phase of Solar Cycle 25 (SC25). We are especially interested to study the role of asymmetric Joule Heating (JH) in the structuring of the Equatorial Ionization Anomaly (EIA), such as double crest, single crest, or merged, which may lead to the formation or suppression of post-sunset ionospheric plasma irregularities. For this purpose, we use the Weimer 2005 Model simulations to analyze the JH patterns during the four strong geomagnetic storms, and Madrigal TEC maps are used to observe changes in the intensity, location, and symmetry of the EIA during these disruptive times. Equatorial/low-latitude ionospheric plasma irregularities at different longitudes under geomagnetically disturbed conditions are studied using the Rate of Change TEC Index (ROTI), which is calculated from GPS receiver measurements. A strong JH is observed during the May 2024 storm (also known as the Mother's Day storm) during its main phase, which occurs after sunset between 18:00 and 00:00 UT. The other storms have the JH strength in the following order from strong to weak: March 2023, April 2023, and November 2023. Besides inter-hemispheric asymmetry, all the storms show stronger variation in the JH patterns. We conclude that the resulting change in the thermospheric winds and electric fields due to storm conditions alter the EIA structures. It has been found that the generation of ionospheric plasma irregularities and their geographical distribution strongly depend on EIA's density gradients and general structure. For instance, it is noticed that the double crest EIA structures with strong plasma density gradients play important role to the generation of post sunset ionospheric plasma irregularities during the main phases of these geomagnetic storms. On the other hand, the single crest or merged EIA structure comprise of a diffuse region of high electron density centered directly over the equator, without a pronounced trough, as observed during the storm of November 2023. The single crest EIA exhibit nearly uniform plasma density distribution do not favor the generation of ionospheric plasma irregularities. The role of storm-time penetrating electric field in the structuring and seeding of ionospheric plasma irregularities has been investigated. The research will contribute to our understanding of the basic physics of the ionosphere, especially the mechanisms governing the development and evolution of the EIA and ionospheric plasma irregularities under various magnetically disturbed conditions. (10.5194/egusphere-2025-86)
  DOI : 10.5194/egusphere-2025-86
• Impact of pressure anisotropy on the cascade rate of Hall magnetohydrodynamic turbulence with biadiabatic ions
  
  • Simon Pauline A
  • Sahraoui Fouad
  • Galtier Sébastien
  • Laveder Dimitri
  • Passot Thierry
  • Sulem Pierre-Louis
  Physical Review E, American Physical Society (APS), 2025, 111 (1), pp.015210. The impact of ion pressure anisotropy on the energy cascade rate of Hall-MHD turbulence with biadiabatic ions and isothermal electrons is evaluated in three-dimensional direct numerical simulations, using the exact (or third-order) law derived by Simon and Sahraoui in 2022. It is shown that pressure anisotropy can enhance or reduce the cascade rate, depending on the scales, in comparison with the prediction of the exact law with isotropic pressure, by an amount that correlates well with pressure anisotropy, $a_p = p_⊥ / p_∥ ≠ 1$, that develops in simulations initialized with an isotropic pressure ($a_{p0} = 1$). A simulation with initial pressure anisotropy $a_{p0} = 4$ confirms this trend, exhibiting a stronger impact on the cascade rate, both in the inertial range and at larger scales, close to the forcing scales. Furthermore, a Fourier-based numerical method, to compute exact laws in numerical simulations in the full ($ℓ_⊥ , ℓ_∥$) increment plane, is presented. (10.1103/PhysRevE.111.015210)
  DOI : 10.1103/PhysRevE.111.015210
• Derivation of a 4-moment model for electron transport in Hall thrusters from a gyrokinetic model
  
  • Tazakkati Zoubaïr
  • Laguna Alejandro Alvarez
  • Massot Marc
  • Pichard Teddy
  , 2025. <div><p>We model the motion of a population of electrons in a strong electromagnetic field undergoing elastic electron/electron collisions. This regime is derived from a dimensional analysis of the electron confinement in Hall-effect thrusters. The electrons exhibit a very high cyclotron frequency and a E × B-drift, modelled by stiff PDEs at the mesoscopic scale. We obtain a gyrokinetic model in which the fastest oscillations of the system are filtered out by averaging the rotation of the electrons around the magnetic field lines. The model is derived in the strong electromagnetic field limit. Based on this gyrokinetic model, we then develop a 10-moment model. The averaging operation performed at the kinetic scale leads to symmetry properties that allow to reduce the 10-moment model to a 4-moment model.</p></div>
• Step-by-step verification of particle-in-cell Monte Carlo collision codes
  
  • Parodi Pietro
  • Petronio Federico
  Physics of Plasmas, American Institute of Physics, 2025, 32 (1). The particle-in-cell (PIC) method with Monte Carlo collisions (MCC) is widely used in the simulation of non-equilibrium plasmas for electric propulsion and laboratory applications. Due to the simplicity of the basic PIC algorithm and the specific modeling needs of the different research groups, many codes have been independently developed. Verification of these codes, i.e., ensuring that the computational code correctly implements the intended mathematical models and algorithms, is of fundamental importance. Different benchmark cases, such as one from Turner et al. [Phys. Plasmas 20, 013507 (2013)], Charoy et al. [Plasma Sources Sci. Technol. 28, 105010 (2019)], and Villafana et al. [Plasma Sources Sci. Technol. 30, 075002 (2021)], have been published in recent years. These have consisted of a complex physical setup, in which many computation modules interact to yield the final result. Although this approach has the advantage of testing the code in a realistic case, it may hide some implementation errors. Moreover, in the case of disagreement, the previous works do not provide an easy way to identify the faulty code modules. In this work, we propose a step-by-step approach for the verification of PIC-MCC codes in a 2D-3V electrostatic setup. The criteria for the test cases are (i) they should highlight possible implementation errors by testing the modules separately, whenever possible (ii) they should be free from physical instabilities to avoid chaotic behavior, and (iii) the numerical result should be accompanied by analytical calculations, for confirmation purposes. The seven test cases identified all show excellent agreement between the authors' codes. (10.1063/5.0241527)
  DOI : 10.1063/5.0241527
• Spatio-temporal features of ionospheric disturbances resulting from March 2023 geomagnetic storm: Comparisons with March 2015 St. Patrick’s Day storm
  
  • Younas Waqar
  • Khan Majid
  • Amory-Mazaudier C.
  • Nishimura Yukitoshi
  • Kamran M.
  Advances in Space Research, Elsevier, 2025, 75 (2), pp.2433-2448. This study explores the ionospheric disturbances induced by the March 2023 geomagnetic storm, offering insights into the complex interplay between space weather events and the Earth’s upper atmosphere. In this regard, data from ionospheric maps (global and regional electron contents) and topside plasma density (provided by the Swarm satellites) have been used. Furthermore, the findings are compared with those of the March 2015 St. Patrick’s Day storm of solar cycle 24, which exhibited notably similar onset conditions. The Global Electron Content (GEC) displays substantial positive surges in the African, Pacific, and American sectors, with a notable enhancement in the American sector on March 24, 2023. During the recovery phase (March-23 storm), negative storm effects are observed across all longitudinal sectors, with greater intensity at low-latitudes compared to mid-latitudes. Moreover, the study highlights discrepancies in positive storm effects when compared to the St. Patrick’s Day storm. During the March-2023, there was no positive storm effect observed in the pacific mid-latitude regions. This longitudinal difference in occurrence of positive storm may be attributed to potential influences from variations in the z-component of the interplanetary magnetic field and energy inputs into the magnetosphere. A super fountain effect is observed exclusively in the American sectors during both storms, exhibiting a noticeable hemispheric asymmetry. The non-uniform planetary distribution of disturbed thermospheric winds likely played a major role in the ionospheric asymmetry in the American region during the 2023 event. (10.1016/j.asr.2024.10.042)
  DOI : 10.1016/j.asr.2024.10.042
• Quantum Offset of Velocity Imaging-Based Electron Spectrometry and the Electron Affinity of Arsenic
  
  • Blondel Christophe
  • Drag Cyril
  Physical Review Letters, American Physical Society, 2025, 134 (4), pp.043001. Electron imaging has been routinely used for electron spectrometry. It has been ignored, however, that the maximum-intensity circles that surround electric field-produced electron spots do not materialize envelopes of trajectories, but the first interior fringes of a caustic. Neglecting the gap between the fringe and the parent envelope has resulted in spectrometric errors, notably on some reference values of electron affinities. Evidence for the effect is given by photodetachment microscopy of O- and a measurement of the electron affinity of ⁷⁵As, which is found to be 0.804486(3) eV. (10.1103/PhysRevLett.134.043001)
  DOI : 10.1103/PhysRevLett.134.043001
• Ion-rich acceleration during an eruptive flux rope event in a multiple null-point configuration
  
  • Pesce-Rollins Melissa
  • Mackinnon Alexander
  • Klein Karl-Ludwig
  • Russell Alexander
  • Hudson Hugh
  • Warmuth Alexander
  • Wiegelmann Thomas
  • Masson Sophie
  • Parnell Clare
  • Nitta Nariaki V
  • Omodei Nicola
  The Astrophysical Journal, American Astronomical Society, 2025, 989 (2), pp.148. We report on the $γ$-ray emission above 100~MeV from the GOES M3.3 flare SOL2012-06-03. The hard X-ray (HXR) and microwave emissions have typical time profiles with a fast rise to a well-defined peak followed by a slower decay. The $&gt;$100~MeV emission during the prompt phase displayed a double-peaked temporal structure with the first peak following the HXR and microwaves, and the second one, about three times stronger, occurring $17 \pm 2$ seconds later. The time profiles seem to indicate two separate acceleration mechanisms at work, where the second $γ$-ray peak reveals a potentially pure or at least largely dominant ion acceleration. The Atmospheric Imaging Assembly imaging shows a bright elliptical ribbon and a transient brightening in the north-western (NW) region. Nonlinear force-free extrapolations at the time of the impulsive peaks show closed field lines connecting the NW region to the south-eastern part of the ribbon and the magnetic topology revealed clusters of nulls. These observations suggest a spine-and-fan geometry, and based on these observations we interpret the second $γ$-ray peak as being due to the predominant acceleration of ions in a region with multiple null points. The $&gt;$100 MeV emission from this flare also exhibits a delayed phase with an exponential decay of roughly 350 seconds. We find that the delayed emission is consistent with ions being trapped in a closed flux tube with gradual escape via their loss cone to the chromosphere. (10.3847/1538-4357/adeb7f)
  DOI : 10.3847/1538-4357/adeb7f