Publications

2026

• STAFF Instrument Calibration, Sensitivity, and Performance Evolutions During the Cluster Mission
  
  • Canu P.
  • Bouzid V.
  • Piberne R.
  • Cornilleau-Wehrlin N.
  • Katra R.
  • Carr C.
  • Alconcel L.
  • Yearby K.
  • Robert P.
  • Lacombe C.
  • de Conchy Y.
  • Grison B.
  • Santolik O.
  • Soucek J.
  • Le Contel O.
  • Baraka M.
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2026, 131 (6). The Spatio‐Temporal Analysis of Field Fluctuations (STAFF) instruments onboard the Cluster satellites were designed to measure magnetic fluctuations in the 0.2–12 Hz and 0.2–180 Hz frequency ranges from the Search‐Coil Magnetometer (SCM), as well as electromagnetic spectra from the Spectrum Analyzer (SA) in the 8–4,000 Hz range. They provided a considerable amount of data throughout the 24‐year mission. The production and calibration of these data sets were detailed in Robert et al. (2014, https://doi.org/10.5194/gi‐3‐153‐2014 ), which demonstrated its excellent quality and good agreement with the fluxgate magnetometer (FGM) measurements over their common frequency range. The Cluster's 24 years of operation, which far exceed the nominal 2‐year mission, represent the longest flight of search coil magnetometers and offer a unique opportunity to evaluate their performance over such a long period, as well as to compare the results of four initially identical instruments. The present work, based on data now archived at the Cluster Scientific Archive (CSA), examines the evolution of these products after the first 11 years in space, and until the end of the Cluster operations in September 2024. The quality of the measurements, calibration, sensitivities, and their agreement between spacecraft proved to be excellent and remained stable throughout the mission. Comparison of spectra derived from the calibrated waveforms of STAFF (CWF) and FGM shows a very good agreement until the end of operations, a further proof of the high quality of their respective calibrations. (10.1029/2026JA035072)
  DOI : 10.1029/2026JA035072
• Analysis of Geomagnetically Induced Currents (GICs) during the May 2024 Gannon storm
  
  • Amaechi Paul O
  • Grodji Franck O
  • Messanga Honore
  • Despirak Irina
  • Ngwira Chigomezyo M
  • Akala Andrew
  • Oyeyemi Elijah
  • Amory-Mazaudier Christine
  • Nishimura Yukitoshi
  • Weygand James M
  Advances in Space Research, Elsevier, 2026. The May 2024 Gannon storm, one of the most intense geomagnetic disturbances (GMDs) in two decades, provides a valuable opportunity to examine geomagnetically induced currents (GICs), their drivers, and impacts on bulk power system resilience. We analyzed GICs over the United States using direct measurements from three North American Electric Reliability Corporation (NERC) monitoring devices, magnetometer-derived proxy indices, and continuous wavelet transform (CWT). The storm featured multiple substorm onsets, supersubstorms (SSSs), and westward electrojet (WEJ). Results show that during the sudden storm commencement on 10 May, magnetic field variations, |dH/dt| reached 80 nT/min at ~54 o MLAT with GICs of up to 70 A recorded by device 10659 (~54 o MLAT) at about 17:08 UT. During the main phase on 10 May, GICs peaked at 128 A at device 10659 around 21:44 UT due to substorm activity in conjunction with Ps6 pulsations. Furthermore, the substorm onset at ~02:00 UT on 11 May was associated with an enhanced |dH/dt| of 437 nT/min at ~56 o MLAT and the largest GIC response to this GMD with a peak of 176 A (device 10659) at 02:04 UT. CWT analysis further suggests that Ps6 magnetic pulsations contributed as secondary driving mechanisms. The recovery phase was characterized by significant GICs up to 120 A at the same device around 08:41 UT, related to coupled magnetospheric drivers, including Pc5 magnetic pulsations and a SSS under magnetic cloud conditions. This storm phase further featured a GIC of 91 A (at 04:32 UT) associated with substorm activity detected during the high-speed stream on 12 May. The study highlights the role of substorms, SSSs, and associated localized magnetic disturbances driven by distinct ICME features, in generating substantial GICs during the recovery phase of intense storms, emphasizing their critical impact on space-weather hazards. (10.1016/j.asr.2026.06.055)
  DOI : 10.1016/j.asr.2026.06.055
• Analyse du bilan (BGES) des activités spatiales du LPP
  
  • Rezeau Laurence
  • Sahraoui Fouad
  , 2026. L'outil GES 1point5 de Labos1point5 permet d'obtenir de manière simple un bilan des émissions de gaz à effet de serre associées aux activités de recherche effectuées hors du laboratoire, ce qui se résume pour le LPP essentiellement à l'exploitation des données des missions spatiales. Le résultat obtenu varie dans des proportions importantes d'une année sur l'autre, ce qui rend l'analyse compliquée puisque l'activité réelle de l'équipe n'est pas si variable. Nous analyserons comment ce résultat est lié à notre activité réelle. Nous comparerons la méthode de calcul, initiée par les collègues de l'IRAP, avec celle qui est utilisée pour les autres « grands instruments » dont les émissions sont prises en compte par Labos1point5. L'objectif de ces calculs de bilan est d'avoir un instrument pour évaluer les évolutions de l'impact de notre activité d'une année sur l'autre dans le but de tenter de diminuer cet impact sans dégrader la qualité de la science produite. Nous nous interrogerons sur ce qui est possible pour améliorer le « thermomètre » et le bilan des missions spatiales.
• Operational space exploration of the X-Point Radiator scenario in WEST
  
  • Rivals N
  • Fedorczak N
  • Geulin E
  • Nouailletas R
  • Moiraf D
  • Yang H
  • Havlickova E
  • Meng L
  • Guillemaut C
  • Gunn J P
  • Hennequin P
  • Morales J
  • Manas P
  • Fevre L
  • Gaspar J
  • Ekedahl A
  • Gerardin J
  • Corre Y
  • Maget P
  • Bernert M
  • Henderson S
  • Reimerdes H
  • Tsitrone E
  • Vianello N
  , 2026. Operational space exploration of the X-Point Radiator scenario in WEST
• Evidence of Langmuir/ Z -mode Wave Decay into Z -mode Electromagnetic Radiation in the Solar Wind
  
  • Polanco-Rodríguez F J
  • Krafft C.
  • Savoini P.
  The Astrophysical Journal Letters, Bristol : IOP Publishing, 2026, 1002 (2), pp.L35. The nonlinear decay of Langmuir/ Z -mode waves into electromagnetic Z -mode wave radiation near the plasma frequency is observed for the first time in the solar wind, during the encounter of the Solar Orbiter satellite with an electron beam associated with a type III radio burst. This result was achieved through the high-resolution electric and magnetic field measurements provided by the Radio Plasma Waves instrument on board the spacecraft. The decay process is identified through multiple lines of evidence: satisfaction of Doppler-shifted frequency resonance conditions, strong phase coherence and temporal coincidence between the interacting waves, dominance over competing mechanisms, and full agreement with theoretical predictions. Two-dimensional particle-in-cell simulations, conducted under close beam-plasma conditions, successfully reproduce the key features of the observations. Notably, they suggest that the wave packet observed by Solar Orbiter may be trapped within an extended, nearly flat-bottomed density well, where the decay process is not overcome by wave scattering on random density fluctuations and subsequent mode conversion effects. (10.3847/2041-8213/ae626f)
  DOI : 10.3847/2041-8213/ae626f
• In-flight performance and first scientific observations of the Search-Coil Magnetometer (SCM) of the Radio and Plasma Waves Investigation (RPWI) onboard the ESA JUICE mission
  
  • Le Khanh T. N.
  • Retino Alessandro
  • Le Contel Olivier
  • Mansour Malik
  • Faure Thomas
  • Baraka Mohammed
  • Stassen Theo
  • Chust Thomas
  • Mirioni Laurent
  • Piberne Rodrigue
  • Santolik Ondrej
  • Soucek Jan
  • Pisa David
  • Khotyaintsev Yuri
  • Cecconi Baptiste
  • Wahlund Jan-Erik
  • Bergman Jan
  • Brown P.
  • Dougherty Michele
  • Masters Adam
  • Barabash S.
  , 2026. 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 scientific observations obtained during its cruise phase, including those from the Lunar-Earth Gravity Assist (LEGA) in August 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-egu26-21140)
  DOI : 10.5194/egusphere-egu26-21140
• Experiments and SOLEDGE modelling of X-Point Radiator regimes in WEST
  
  • Rivals N
  • Fedorczak N
  • Yang H
  • Fèvre L
  • Orlacchio F
  • Havlickova E
  • Team West
  , 2026. <div><p>Particle flux to divertor plate Plasma density "Detachment": reduction of particle flux "XPR": Stable toroidal radiation ring located at the X-Point, (= "stable MARFE"), observed in many machines, associated with divertor heat flux reduction Colloque FR-FCM -N.</p></div>
• Theoretical ion sputtering yields from loose powders using a multiscale Monte Carlo approach
  
  • Verkercke Sébastien
  • Berhanu D
  • Bu C
  • Clouter-Gergen B
  • Leblanc François
  • Lewis J R
  • Morrissey L S
  • Savin D W
  Journal of Applied Physics, American Institute of Physics, 2026, 139, pp.145302. <div><p>Ion sputtering from loose powders remains poorly understood despite its relevance to planetary science and industry. We developed a multiscale Monte Carlo model to simulate sputtering from powders, using a higher-fidelity approach for the target geometry compared to voxelbased methods. Simulating Kr + ions impacting Cu powders and flat slabs, we show that sputtering from loose powders differs markedly from that of flat slabs or rough surfaces. The main differences are: (1) for incident angles α &gt; 0°relative to the bulk normal, the escaping sputtering yield is dominated by backward-directed ejecta for all ion energies; (2) for α ≤ 60°, the yield peaks toward the ion-beam origin, similar to the opposition effect seen in optical observations of airless bodies; (3) the angular distribution peak is half or less than that of a flat slab; (4) as ion energy increases, no evolution occurs from primary to secondary knock-on sputtering in the ejecta angular distribution. We attribute these behaviors to the powder's interconnected voids. Ions penetrate these voids and sputter underlying grains; the ejecta then preferentially escape toward the ion-beam origin, where shadowing is minimal. We derive two fitting functions: (1) relating the escaping sputtering yield of a powder to that of a flat surface, depending only on porosity, incident angle, mean local incidence angle, and the corresponding flat slab yield; (2) providing the double-differential angular distribution of the escaping ejecta for porosities ≥0.49. These provide a potentially universal fitting function of the absolute doubly differential escaping sputtering yield from loose powders.</p></div> (10.1063/5.0316828)
  DOI : 10.1063/5.0316828
• Low‐Pressure Microwave Air Plasma Decontamination of Black Pepper ( Piper nigrum ): From Microbial Efficacy to Quality Preservation
  
  • Soulier Manon
  • Kais Abderrahmane
  • Maho Thomas
  • Guillot Philippe
  • Muja Cristina
  Plasma Processes and Polymers, Wiley-VCH Verlag, 2026, 23 (4). ABSTRACT This study investigates low‐pressure microwave air plasma as a non‐thermal decontamination approach for spices, using black peppercorns as a model matrix. At 20 Pa and 80 W, the discharge exhibits electron densities of 10 9 –10 10 cm −3 , effective electron temperatures of 0.7 eV, while keeping the substrate temperature below 60°C. Under these conditions 1.2‐log reduction of native aerobic mesophilic and thermophilic flora is achieved after 60 min. Bacillus subtilis spores on peppercorns show a similar 1.2‐log reduction, versus > 6‐log on flat glass carriers, revealing a strong surface shielding effect. UV radiation drives early spore inactivation, while long‐lived reactive species contribute during prolonged exposures. These antimicrobial effects are achieved without significant compromise of the key quality attributes of black pepper. (10.1002/ppap.70165)
  DOI : 10.1002/ppap.70165
• White paper on the relevance of the European Solar Telescope (EST) for the French heliophysics community
  
  • Pariat Etienne
  • Noraz Quentin
  • Perri Barbara
  • Poirier Nicolas
  • Froment C.
  • Bigot Lionel
  • Aulanier Guillaume
  • Gelly Bernard
  • Aboudarham Jean
  • Aizawa Sae
  • Alexandrova Olga
  • Alqeeq Soboh
  • Amari Tahar
  • Auchère Frédéric
  • Bernoux Guillerme
  • Berthomier Matthieu
  • Bommier Veronique
  • Bonnin Xavier
  • Brun Allan Sacha
  • Bualé Isabelle
  • Buchlin Éric
  • Canou Aurélien
  • Canu Patrick
  • Corbard Thierry
  • Cornu Florence
  • Coustillet Camille
  • Cozzani Giulia
  • D’herbomez Léa
  • Diaz Castillo Saida
  • Dudok de Wit Thierry
  • Faurobert Marianne
  • Finley Adam
  • Fontaine Dominique
  • Garcia Rafael A.
  • Grappin Roland
  • Hadid Lina
  • Henadhira Arachchige Kalpa Harindra Perera
  • Janvier Miho
  • Jouve Laurène
  • Kieokaew Rungployphan
  • Kirkwood Hannah
  • Lavraud Benoit
  • Le Breton Jean-Pierre
  • Le Contel Olivier
  • Le Nestour Nicolas
  • Leblanc François
  • Masson Sophie
  • Meyer-Vernet Nicole
  • Parenti Susanna
  • Pitout Frédéric
  • Rieutord Michel
  • Romero Castañeda Jorge
  • Rouillard Alexis
  • Ruiz de Galarreta Claudia
  • Sahraoui Fouad
  • Schmieder Brigitte
  • Simon Pauline
  • Strugarek Antoine
  • Tallon Michel
  • Thepthong Panisara
  • Touresse Jade
  • Vial Jean-Claude
  • Vilmer Nicole
  • Zaslavsky Arnaud
  , 2026. The project of the European Solar Telescope aims to provide a state-of-the art infrastructure to study the Sun and its interactions with Earth and the heliosphere. This 4.2m aperture telescope will be equipped with multi conjugate adaptive optics, light-polarisation analyser, imaging spectrograph and integral field unit spectrographs. It will provide unprecedented observations of the solar photosphere and chromosphere and of the dynamical events and features that pertains to the low solar atmosphere. The EST project is presently in a phase of crystallisation, aiming at the creation of an European Research Infrastructure Consortium. While the French community has continuously been associated with the development of the EST project, some specific scientific aspects are more particularly relevant for the French astrophysics and heliophysics communities. The present review highlights the scientific research axes of high interest from the French community that shall strongly benefit from EST. The later will not only advance numerous topics of solar physics, as well as solar adaptive optics developments, but will also provide unrivaled datasets of high interest in the framework of space weather. This review also aims to highlight the space weather use that can be done with future EST observations, that will be particularly relevant for French heliophysicists.
• Magnetic geometry impact on the edge radial electric field in tokamaks
  
  • Rienäcker Sascha
  , 2026. Mitigating plasma turbulence is a major objective of magnetic confinement fusion research,as the resulting transport of heat and particles largely determines confinement quality—and thus, the performance and cost of future fusion power plants.Sheared plasma flows play a central role in regulating turbulent transport, enabling, in particular, the formation of transport barriers associated with high confine-ment regimes. Even in low confinement mode (L-mode), tokamak plasmas typically exhibit, at the edge of the confined region, a narrow Er × B shear layer corresponding to a negative radial electric field (Er)“well”. However, a deep understanding of the role ofthis Er well in setting L-mode confinement proper-ties and in providing access to higher confinement regimes is still lacking. In addition, the sensitivities of Erto plasma conditions remain poorly understood and difficult to capture using existing models or numerical tools. This PhD thesis investigates these sensitivities experimentally to help disentangle the dominant Er drives in L-mode and clarify their role in confinement improvement or transitions. Experiments are primarily conducted on the TCV tokamak, using a newlyinstalled Doppler backscattering (DBS) diagnostic to characterize the edge Er profile. Systematic parameterscans are performed in carefully matched dischargesto isolate the impact of magnetic drift configuration and plasma shaping (specifically, triangularity) on the mean Er and other edge profiles. Overall, the findings support a link between edge Er shear and the influence of magnetic geometry on confinement properties.Combined with recent first-principles simulations, the observations point to the importance of turbulence-driven flow generation in explaining sensitivities of Erto magnetic geometry.
• Comparative physicochemical study of dielectric barrier discharge and post-discharge plasmas to treat non-small cell lung carcinoma in murine models
  
  • Soulier Manon
  • Marmier Solenne
  • Decauchy Henri
  • Cremer Isabelle
  • Dufour Thierry
  Journal of Physics D: Applied Physics, IOP Publishing, 2026, 59 (9), pp.095202. While cold atmospheric plasmas (CAPs) are increasingly explored for cancer therapy, it remains unclear how distinct device configurations translate into differences in tissue coupling, safety, and therapeutic efficacy. To address this gap, a comparative evaluation of the two following CAP sources has been conducted: the ORJET (atmospheric pressure plasma jet in outer ring electrode configuration) and the PoDBD (post-discharge delivered by a dielectric barrier device with a grounded-mesh electrode). Electrical behavior is quantified on an equivalent electrical human body model, while optical emission spectroscopy and surface-oxidation assays are achieved on transdermal membranes and polyethylene substrates to characterize the nature and diffusion of plasma-generated reactive species. Thermal safety is examined in mice through real-time temperature monitoring and histological analysis while antitumor efficacy is determined in a syngeneic model of non-small cell lung cancer (NSCLC) treated five times. The two devices display fundamentally different modes of tissue coupling: ORJET delivers localized interfacial electric field while PoDBD exposes tissue solely to reactive oxygen and nitrogen species-rich post-discharge. Despite these differences, both generate similar reactive-species signatures, preserve tissue integrity when operated within safe thermal limits, and significantly slow tumor progression compared with controls, with no difference between devices. These findings indicate that therapeutic activity arises predominantly from reactive-species chemistry rather than electrical coupling, supporting the applicability of diverse CAP technologies for oncological treatment. (10.1088/1361-6463/ae46ac)
  DOI : 10.1088/1361-6463/ae46ac
• A study of the magnetic effects of the Equatorial Electrojet (EEJ) along the East Asian and West African sectors
  
  • Grodji F.O.
  • Yao H.F.M.
  • Amaechi P.O.
  • Amory-Mazaudier C.
  • Doumbia V.
  • Kouassi N.
  • Kassamba A.A.
  • Tuo Z.
  Advances in Space Research, Elsevier, 2026. This paper presents a comparative analysis of the Equatorial Electrojet (EEJ) effects along the East Asian (140° E) and West African (5° W) sectors using geomagnetic field data recorded in 1993. The data were obtained within the frameworks of the International Equatorial Electrojet Year (IEEY) campaign for West Africa and the Solar-Terrestrial Energy Program (STEP) project for the Asian sector. The analysis was conducted under quiet magnetic conditions (Am < 20 nT) to facilitate the investigation of regular daily variations () induced by the EEJ. Key electrodynamic parameters of the EEJ such as ribbon width, center position, and maximum current intensity were estimated using latitudinal profiles of the H and Z components of the geomagnetic field. The results reveal significant latitudinal and longitudinal variations characterized by a wider EEJ ribbon in Asia (∼714 km) compared to West Africa (∼601 km), and a higher peak current intensity in West Africa (214.3 ± 30.9 A/km) relative to Asia (142.4 ± 31.9 A/km). Also, in 1993, the EEJ centre was located north of the magnetic equator in West Africa and south of it in Asia, indicating a pronounced hemispheric asymmetry. Seasonal variations show higher EEJ intensities during the equinoxes than during the solstices in both longitude sectors. Throughout 1993, the EEJ peak intensity over West Africa consistently surpassed that over East Asia, irrespective of the magnetic season. Furthermore, the frequency of occurrence of the counter-electrojet (CEJ) was higher in West Africa, especially during the morning hours. This study shows that EEJ morphology and strength are modulated by longitude-dependent factors, including ionospheric conductivity, neutral winds, atmospheric tides, and the geomagnetic field. (10.1016/j.asr.2026.03.039)
  DOI : 10.1016/j.asr.2026.03.039
• From electroculture to plasma agriculture: a three-century arc bridging Bertholon’s legacy with contemporary farming advances
  
  • Dufour Thierry
  Comptes Rendus. Mécanique, Académie des sciences (Paris), 2026, 354 (G1), pp.89-116. This review traces the historical trajectory of electricity in agriculture, from the earliest observations of electrical phenomena to the emergence of cold plasmas. Looking back to Antiquity and then to the Enlightenment, it underlines Abbé Bertholon’s 18th-century efforts to channel atmospheric electricity to stimulate crops, using devices such as the electro-végétomètre. Although these early electroculture experiments relied on neither quantitative dosimetry nor rigorous methodology, they foreshadowed the idea of a controlled transfer of electrical energy to plants. Then the review examines the historical development of galvanism, electrochemistry, and the physics of gaseous discharges throughout the 19th and 20th centuries, which collectively laid the foundations for contemporary cold-plasma technologies. In the 21st century, plasma agriculture has emerged as an interdisciplinary approach integrating electrical, chemical, radiative, thermal, and fluid-mechanical effects. Applications include seed treatment (preconditioning, seed priming), stimulation of plant growth, soil and water treatment, and decontamination of agri-food products. The review thus reassesses Abbé Bertholon’s contributions as those of a methodological precursor and shows how his intuition of a “vivifying electricity” resonates with modern cold-plasma science. Finally, it argues that plasma agriculture can transform an Enlightenment intuition into a reproducible experimental framework for sustainable agriculture and food safety. (10.5802/crmeca.331)
  DOI : 10.5802/crmeca.331
• Reactive oxygen species trigger downward vertical migration in diatom microphytobenthic biofilms as a strategy to cope with oxidative stress
  
  • Desparmet Alexandre
  • Jesus Bruno
  • Robinet Tony
  • Dufour Thierry
  • Hubas Cédric
  The International Society of Microbiologial Ecology Journal, Nature Publishing Group, 2026, 20. Diatom-dominated intertidal microphytobenthic biofilms experience daily fluctuations in irradiance, which can lead to oxidative stress within the photosynthetic apparatus through the production and accumulation of reactive oxygen species. To maintain photosynthetic efficiency, benthic diatoms have developed protective strategies, including mobilization of the antioxidant xanthophyll cycle and the ability to migrate vertically through sediments. However, mechanistic understanding of signaling pathways underlying migration remains poorly characterized. This study investigated the triggering effect of reactive oxygen species on behavioral and photophysiological responses through the analysis of lipophilic pigments and fluorescence parameters. To this end, two microphytobenthic communities, one with sediment allowing vertical migration and another without sediment restricting it, were exposed to irradiance, cold atmospheric plasma, and hydrogen peroxide stresses. Results showed a consistent downward migration response under all oxidative stresses, highlighting the key role of reactive oxygen species, especially hydrogen peroxide, in triggering this microphytobenthic behavior. Moreover, a difference was observed between the pathways involved in vertical migration and those underlying photoprotective responses. Hydrogen peroxide and cold atmospheric plasma stresses highlighted the necessity for substantial microphytobenthic migration, whereas irradiance induced a specific and controlled response involving engagement of the xanthophyll cycle, acting in synergy with the migration strategy by showing stronger activation when migration was impaired. By establishing that a rapid and efficient migration could be induced by reactive oxygen species (ROS) and could act in synergy with the xanthophyll cycle in epipelic cells, this study provides key insights into the molecular basis of microphytobenthic responses to cellular and environmental oxidative stresses. (10.1093/ismejo/wrag034)
  DOI : 10.1093/ismejo/wrag034
• Formation of gradients of atomic oxygen in nanosecond plasma for plasma-assisted detonation: experimental and numerical study
  
  • Lafaurie Victor
  • Shu Zhan
  • Zhang B
  • Terentjeviene M
  • Billeau Jean-Baptiste
  • Orel Inna
  • Hoyos Aristizabal Samuel
  • Vidal Pierre
  • Starikovskaia Svetlana
  Plasma Sources Science and Technology, IOP Publishing, 2026, 35 (2), pp.025022. This work aims at producing a gradient of atomic oxygen on a scale of 10 cm in a plane-to-plane nanosecond discharge in 150 mbar of air with a varying gap size for applications in combustion and ignition of detonation waves. Local measurements of atomic oxygen density along the discharge span, at varying heights between high-voltage and grounded electrode, are performed with Xe calibrated O-TALIF and validated by 2D numerical modelling. They both show existence of a gradient of atomic density of oxygen along the span. Reduced electric field is measured with two experimental techniques: optical emission spectroscopy by a spectral band intensity ratio of the first negative system and the second positive system of nitrogen, and E-FISH. It is also compared with numerical modelling. All techniques show existence of a gradient of reduced electric field along the span. This distribution of reduced electric field, in combination with the non-uniform energy deposition in the plasma, is shown to explain the measured gradient of density of atomic oxygen. (10.1088/1361-6595/ae3f53)
  DOI : 10.1088/1361-6595/ae3f53
• Benchmark for two-dimensional large scale coherent structures in partially magnetized E × B plasmas—community collaboration &amp; lessons learned
  
  • Powis Andrew T
  • Ahedo Eduardo
  • Álvarez Laguna Alejandro
  • Barléon Nicolas
  • Bello-Benítez Enrique
  • Beving Lucas
  • Boeuf Jean-Pierre
  • Bogopolsky Guillaume
  • Bourdon Anne
  • Cichocki Filippo
  • Cuenot Bénédicte
  • Denig Andrew
  • Donkó Zoltán
  • Elias Paul-Quentin
  • Encinar Miguel
  • Eremin Denis
  • Fajardo Pablo
  • Faraji Farbod
  • Fubiani Gwenael
  • Garrigues Laurent
  • Hara Kentaro
  • Hartmann Peter
  • Hopkins Matthew
  • Kaganovich Igor D
  • Knoll Aaron
  • Lapenta Giovanni
  • Magin Thierry
  • Marín-Cebrián Alberto
  • Merino Mario
  • Minelli Pierpaolo
  • Papahn Zadeh Mina
  • Parodi Pietro
  • Petronio Federico
  • Reza Maryam
  • Smolyakov Andrei I
  • Sydorenko Dmytro
  • Taccogna Francesco
  • Turner Miles M
  • Vermorel Olivier
  • Villafana Willca
  • Xu Liang
  Plasma Sources Science and Technology, IOP Publishing, 2026, 35 (2), pp.025002. Abstract Low-temperature plasmas (LTPs) are essential to both fundamental scientific research and critical industrial applications. As in many areas of science, numerical simulations have become a vital tool for uncovering new physical phenomena and guiding technological development. Code benchmarking remains crucial for verifying implementations and evaluating performance. This work continues the Landmark benchmark initiative, a series specifically designed to support the verification of LTP codes. In this study, seventeen simulation codes from a collaborative community of nineteen international institutions modeled a partially magnetized E × B Penning discharge. The emergence of large scale coherent structures, or rotating plasma spokes, endows this configuration with an enormous range of time scales, making it particularly challenging to simulate. The codes showed excellent agreement on the rotation frequency of the spoke as well as key plasma properties, including time-averaged ion density, plasma potential, and electron temperature profiles. Achieving this level of agreement came with challenges, and we share lessons learned on how to conduct future benchmarking campaigns. Comparing code implementations, computational hardware, and simulation runtimes also revealed interesting trends, which are summarized with the aim of guiding future plasma simulation software development. (10.1088/1361-6595/ae3985)
  DOI : 10.1088/1361-6595/ae3985
• Evidence of an Extended Alfvén Wing System at Enceladus: Cassini's Multi‐Instrument Observations
  
  • Hadid Lina Z.
  • Chust Thomas
  • Wahlund Jan-Erik
  • Morooka Michiko W
  • Roussos Elias
  • Witasse Olivier
  • Rabia Jonas
  • Pisa David
  • Kim Konstantin
  • Edberg Niklas J T
  • Rymer Abigail M
  • Lamy Laurent
  • Kotsiaros Stavros
  • Aizawa Sae
  • Jeandet Alexis
  • Modolo Ronan
  • André Nicolas
  • Canu Patrick
  • Bowers Charles F
  • Jia Xianzhe
  • Coates Andrew J
  • Jones Geraint H
  • Parsec‐wallis Anna
  • Agiwal Omakshi
  • Holmberg Mika K G
  • Nénon Quentin
  • Cao Hao
  • Kurth William S
  • Dougherty Michele K
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2026, 131 (2). We report in situ evidence for Enceladus' Alfvén wing system and its coupling with Saturn's ionosphere, based on multi-instrument observations from the Cassini spacecraft. Analysis of 36 events, including 13 from non-flyby paths, confirms the existence of a Main Alfvén Wing (MAW) current system generated at Enceladus, and associated Reflected Alfvén Wings (RAWs) occurring both at Saturn's ionosphere and on the density gradient of Enceladus' plasma torus, extending longitudinally to at least ∼ 120°(∼2,000 moon radii) downstream of the moon. Additionally, the observations reveal the systematic existence of a filamentation process of these large-scale Alfvénic perturbations (MAW and RAWs) during their propagation at any distance from their source. These findings demonstrate a more extensive electrodynamic coupling than previously reported for Enceladus and more generally for any moon-magnetosphere interaction. Moreover, the observation of energetic electron depletions and water-group ion signatures at longitudes even further from the moon supports the interpretation of an extended and persistent interaction region. These results highlight Enceladus' role in shaping Saturn's magnetospheric environment and underscore the importance of future missions to exhaustively analyze this type of complex interaction between a moon and a planet. Plain Language Summary Saturn's small icy moon Enceladus interacts with the planet's magnetic field, generating intermittent aurora in Saturn's upper atmosphere and electromagnetic waves that travel along invisible magnetic connections between them. During its 13-year mission, the Cassini spacecraft repeatedly crossed these magnetic field lines linked to Enceladus. We used data from several Cassini instruments to study how energy and particles move between the moon and Saturn. We detected wave activity characteristic of Alfvén waves (similar to vibrations on a string), forming as Saturn's magnetic field flows past Enceladus. Due to a complex system of reflection at both Saturn's ionosphere and the boundary of Enceladus' torus, these waves were found not only near the moon but also trailing far behind it, extending more than 504,000 km (over 2,000 times the moon's radius) behind it. This is the first time that Alfvén waves have been observed to be directly linked to the charged particles associated with Enceladus. This shows that Enceladus plays a much bigger role in shaping Saturn's space environment than previously thought, and reveals how moons can influence their host planet across vast distances. (10.1029/2025ja034657)
  DOI : 10.1029/2025ja034657
• High-order moment closure for nonmagnetized electrons in partially ionized plasmas
  
  • Alvarez Laguna A.
  • Hara K.
  Physical Review E, American Physical Society (APS), 2026, 113 (2), pp.025207. Linearized moment equations are often used to derive closure models for the hydrodynamic equations of multi-component plasmas near thermodynamic equilibrium. However, the linearized transport equations lose their validity in rarefied conditions or in the presence of strong electric fields, when the velocity distribution functions (VDFs) of the different species are non-Maxwellian and the drift between the species, i.e., the Mach number of the relative motion, becomes large. In this paper, we develop a nonlinear, high-order moment model for nonmagnetized electrons in partially ionized plasmas. We present a fourteen-moment model using a Hermitian expansion of the VDF that considers density, momentum, anisotropic pressure tensor, contracted heat flux vector, and contracted scalar kurtosis. We consider the relevant collisional processes in partially ionized plasmas, such as elastic and inelastic electron-neutral, electron-impact ionization, electron-electron Coulomb, and electron-ion Coulomb collisions. The collisional terms in the electron moment equations are integrated analytically for finite Mach numbers and accounting for the nonlinear terms in the Boltzmann operator, which are often neglected in linearized closure models. The proposed closure presents novel cross-coupling effects between moments of different tensorial nature within the collisional terms. The present nonlinear fourteen-moment model is benchmarked against a Monte Carlo simulation under a spatially homogeneous configuration, showing good agreement for a wide range of reduced electric field (e.g., up to 1000 Td) before runaway electrons occur, improving the results of a linear fourteen-moment model. (10.1103/lm1z-bzt3)
  DOI : 10.1103/lm1z-bzt3
• Magnetic reversals in a geodynamo model with a stably–stratified layer
  
  • Müller Nicolás P
  • Gissinger Christophe
  • Pétrélis François
  Physics of the Earth and Planetary Interiors, Elsevier, 2026, 371, pp.107502. We study the process of magnetic reversals in the presence of a stably-stratified layer below the core-mantle boundary using direct numerical simulations of the incompressible magnetohydrodynamics equations under the Boussinesq approximation in a spherical shell. We show that the dipolar-multipolar transition shifts to larger Rayleigh numbers in the presence of a stably-stratified layer, and that the dipolar strength of the magnetic field at the core-mantle boundary increases due to the skin effect. By imposing an heterogeneous heat flux at the outer boundary, we break the equatorial symmetry of the flow, and show that different heat flux patterns can trigger different dynamo solutions, such as hemispheric dynamos and polarity reversals. Using kinematic dynamo simulations, we show that the stably-stratified layer leads to similar growth rates of the dipole and quadrupole components of the magnetic field, playing the role of a conducting boundary layer, favouring magnetic reversals, and a dynamics predicted by low-dimensional models. (10.1016/j.pepi.2026.107502)
  DOI : 10.1016/j.pepi.2026.107502
• Plasma plume symmetrization by electron rotation and ion detachment properties in a diverging magnetic nozzle
  
  • Pioch Romain
  • Chabert Pascal
  • Désangles Victor
  Physical Review E, American Physical Society (APS), 2026, 113 (3), pp.035209. The ion flux direction in a rapidly diverging magnetic field and the role of Earth's magnetic field in plasma dynamics are investigated experimentally using a low power electron cyclotron resonance thruster. The comparison between ion trajectories measured with a directional Faraday cup and the magnetic field geometry allows us to assess some of the ion flow properties. The results show that the ion trajectories follow the magnetic field lines in the center part of the plasma plume but not on its edges, defining the detachment location. Once detached, ions follow straight line trajectories, and their detachment has a divergent nature. The effect of the thruster operating condition on these properties is explored. Plasma potential measurements carried out with an emissive probe reveal the presence of a large radial electric field, pointing outward at the detachment point, that explains the divergent nature of the ion detachment. The amplitude of the induced E × B drift rotation of the electrons in the nozzle damps the disymmetrizing influence of Earth's magnetic field on the electron dynamics and leads to an axisymmetric plasma plume. This mechanism is demonstrated using single particle simulations. (10.1103/3twz-bcvk)
  DOI : 10.1103/3twz-bcvk
• Towards Gravitational Wave Turbulence within the Hadad-Zakharov metric
  
  • Gay Benoît
  • Babichev Eugeny
  • Galtier Sébastien
  • Noui Karim
  Phys.Rev.D, 2026, 113 (12), pp.124074. The theory of gravitational wave turbulence describes the long-term statistical behaviour of a set of weakly nonlinear interacting waves. In this paper, we aim to study aspects of gravitational turbulence within the framework of general relativity using the Hadad-Zakharov (HZ) metric. The latter is parameterised by four functions (the coefficients of a diagonal metric) that must satisfy seven non-trivial Einstein equations, six of which are independent. The issue of their mutual compatibility is therefore essential, yet it has so far been overlooked. In this work, we argue that these equations can be compatible in the weakly nonlinear regime under specific conditions. Our analytical investigation is complemented by direct numerical simulations performed with a new GPU-based code, TIGER. A comparative analysis of the evolution of the Ricci and Kretschmann scalars indicates that gravitational wave turbulence corresponds to the propagation of a genuine physical degree of freedom. These numerical findings, however, must be interpreted with caution, given the difficulty of satisfying all seven Einstein equations simultaneously with sufficient accuracy. On the other hand, our simulations reproduce well the expected properties of the wave turbulence regime, with the emergence of a dual cascade of energy and wave action, and for the latter the observation of the Kolmogorov-Zakharov spectrum. In addition, our analysis reveals that the canonical variables of the problem evolve towards a nearly Gaussian statistical distribution punctuated by intermittent coherent (spatially localised and long-living) structures. In contrast to the canonical variables, the structure functions of the gauge-invariant metric components exhibit monofractal behaviour, which is a classical property of wave turbulence. (10.1103/vc5p-c3w8)
  DOI : 10.1103/vc5p-c3w8
• Equatorial ionospheric plasma bubbles during intense geomagnetic storms of Solar Cycle 25
  
  • Imtiaz Nadia
  • Calabia Andres
  • Anoruo Chukwuma
  • Zahid Aqsa
  • Amory-Mazaudier Christine
  • Adhikari Binod
  Annales Geophysicae, European Geosciences Union, 2026, 44 (1), pp.489-509. This study examines the low-latitude ionospheric response to four intense geomagnetic storms during Solar Cycle 25 (March, April, November 2023, and May 2024), focusing on Equatorial Ionization Anomaly (EIA) variations and post-sunset plasma irregularities. We used the Weimer (2005) model for Joule Heating (JH), Madrigal total electron content (TEC) maps, and GNSS-derived ROTI to analyze storm-time changes in EIA structure and equatorial plasma bubbles (EPBs). The May 2024 storm exhibited the strongest post-sunset JH, particularly near the June solstice, while March and April storms showed moderate JH and November the lowest. Equinox storms produced nearly symmetric JH patterns, while solstice storms revealed interhemispheric asymmetries. Following JH thresholds are used for the classification of storms: weak (20–30 mW m−2, November), moderate (30–50 mW m−2, March/April) and strong (&gt;50 mW m−2, May). JH, together with storm-time electric fields and equatorial meridional winds, influence the location, strength, hemispheric asymmetry, and the generation or suppression of plasma irregularities of the EIA crest. The generation of ionospheric plasma irregularities and their geographical distribution strongly depend on EIA's density gradients and general structure. Well-developed double-crest EIAs with steep density gradients favor post-sunset irregularities, while single-crest or merged EIAs are less favorable. Fluctuations in the IMF Bz drive east-west prompt penetration electric fields that dynamically modulate the F region, altering the plasma fountain effect, the EIA structure, and the distribution of plasma bubbles after sunset. These results suggest that during geomagnetic storms, the combined effects of storm-driven electrodynamics and neutral winds modulate low-latitude ionospheric variability, influencing EIA dynamics and the formation of plasma irregularities. (10.5194/angeo-44-489-2026)
  DOI : 10.5194/angeo-44-489-2026
• Climatology of Plasma Irregularities Using ROTI Index From 2008 to 2023 in East West Asia
  
  • Drabindra Pandit
  • Rolland Fleury
  • Christine Amory‐mazaudier
  Space Weather: The International Journal of Research and Applications, American Geophysical Union (AGU), 2026, 24 (4), pp.e2025SW004759. This study investigates characteristics of ionospheric irregularities over the East–West Asian equatorial region using the Rate of TEC Index (ROTI) derived from Global Navigation Satellite System (GNSS) measurements. Data from four stations (GUAM, PIMO, CUSV, and IISC) were analyzed for 2008–2023, covering solar cycle (SC) 24 and the ascending phase of SC 25. While our findings are generally aligned with previous research, this work presents new insights into the complex behavior of ionospheric scintillation in this sector. A key finding is the significant spatial variability in irregularity occurrence, with stations at similar magnetic dip (11–13°) exhibiting varying activity levels. Notable longitudinal asymmetries were also identified, particularly at GUAM, which shows reduced autumnal activity, likely due to local differences in Pre‐Reversal Enhancement (PRE) and magnetic declination. Our study shows a clear daily pattern: scintillation begins after sunset (18:00–19:00 LT), peaks in the late evening (20:00–21:30 LT), and declines by early morning. A slight increase in ROTI is consistently observed just before sunrise at all locations. Temporally, results show dependence on the 11‐year SC and a distinct seasonal pattern, with activity concentrated in equinoctial months. The spring maximum is generally stronger than the autumn one across stations. Finally, although the long‐term trend follows the SC, the relationship is non‐linear. Outliers, such as anomalous activity in 2019, demonstrate that while the Sunspot Number (SSN) is a primary long‐term driver, scintillation is also modulated by short‐term geophysical phenomena. (10.1029/2025SW004759)
  DOI : 10.1029/2025SW004759
• Electron temperatures in the ionosphere of Venus from Solar Orbiter/Radio and Plasma Waves instrument
  
  • Vecchio A.
  • Maksimovic M.
  • Galand M. I. F.
  • Bonnin X.
  • Astier P.-L.
  • Edberg N. J. T.
  • Píša D.
  • Boldú J. J.
  • Matteini L.
  • Chust T.
  • Hadid L. Z.
  • Kretzschmar Matthieu
  • Khotyaintsev Yu. V.
  • Souček J.
  • Horbury T.
  • Bale S. D.
  Astronomy & Astrophysics - A&A, EDP Sciences, 2026, 709. Context. On February 18, 2025, Solar Orbiter (SO) completed its fourth gravity assist maneuver of Venus (VGAM4) and reached an unprecedented proximity coming within 378 km of the planet. This flyby was necessary to steer the spacecraft into an orbit outside the plane of the ecliptic. Near the closest approach, only the Radio and Plasma Wave (RPW) and Magnetometer (MAG) instruments were operational; this enabled high-cadence measurements to be taken to investigate the plasma properties of the Venusian ionosphere. Aims. The main goal of this study is to derive the electron density and temperature in the ionosphere of Venus using electric potential measurements from RPW, and to characterize them. Methods. During approximately five minutes around the closest approach, the High Frequency Receiver of RPW detected radio emissions of a type naturally generated by planetary ionospheres whose frequency can be related to the electron density. Using quasithermal noise spectroscopy, we inferred the electron temperature at discrete altitudes and solar zenith angles. Results. Solar Orbiter measured an average density and electron temperature in the ionosphere of Venus of 12 385 ± 148 cm⁻³ and 0.43 ± 0.05 eV, respectively. These values are in agreement with in-situ measurements by Pioneer Venus Orbiter (PVO) obtained at the solar maximum. Binned magnetic fields and temperatures are anticorrelated, which suggests that the magnetic flux ropes, observed in the Venus ionosphere, are more likely non-force-free structures. Conclusions. The findings presented in this paper, together with the measurement from the Parker Solar Probe (PSP) during the third gravity assist, support the conclusion that the plasma density in the Venusian ionosphere above 350 km varies with solar activity, whereas the electron temperature shows a much weaker dependence. Notably, the electron temperature remains consistent across the three missions (SO, PSP, and PVO), despite varying levels of solar activity. This suggests that, over the altitude and solar zenith regions probed, the thermal structure of the Venusian ionosphere is not driven by solar extreme ultraviolet (EUV) heating alone, but is also shaped by external heat sources near the ionopause. Processes such as the damping of whistler mode waves, solar wind ion heating, and thermal conduction from the hot ionosheath appear to play a major role. (10.1051/0004-6361/202557868)
  DOI : 10.1051/0004-6361/202557868