Publications

2025

• Treatment of sunflower seeds by cold atmospheric plasma enhances their tolerance to water stress during germination and early seedling development
  
  • Taras L
  • Bailly C
  • Dufour Thierry
  Journal of Physics D: Applied Physics, IOP Publishing, 2025, 59 (1), pp.015210. The aim of this study was to investigate the impact of ambient air plasma treatment on both sunflower seed germination and early steps of seedling development under water stress. Dry seeds were exposed to a cold atmospheric plasma (CAP) generated in a dielectric barrier device where excited molecular nitrogen and ozone were detected by optical emission spectroscopy and mass spectrometry respectively. Interestingly, we explain the crucial role of gap’s accuracy when treating seeds with CAP, especially to improve interaction between seeds and plasma and therefore ensure an efficient treatment. CAP significantly improved the germination rates of seeds of dormant and non-dormant sunflower genotypes under water stress, demonstrating its efficiency in alleviating seed dormancy and in improving germination under suboptimal conditions. Furthermore, greenhouse experiments demonstrated that plasma treatment also stimulated seedling development under water stress conditions. These findings highlight the potential of CAP treatment as an effective approach to promote the whole process of emergence of crop species. (10.1088/1361-6463/ae2ae6)
  DOI : 10.1088/1361-6463/ae2ae6
• On the use of moment methods for modeling low-temperature plasmas in the low and intermediate pressure regime
  
  • Berger Anatole
  , 2025. Low-temperature plasmas are used inmany technological applications, from micro electronics manufacturing to electric space propulsion. They exhibit strong nonequilibrium features that cannot be described by classical fluid models, and require kinetic models, that are often computationally much more expensive.This thesis investigates the method of moments as an intermediate approach between fluid and kinetic descriptions for low-temperature plasma modeling. This method is based on a hierarchy of equations derived from the kinetic theory, that must be closed to truncate the system.For ions, several 1D five-moment models are considered,including the regularized Grad method, a maximum-entropy approach, and two Gaussian quadrature models (HyQMOM and EQMOM). These models are implemented in numerical simulations with second-order finite-volume schemes, and benchmarked against kinetic simulations, for one-dimensional bounded plasma in a wide range of pressures. The results show that five-moment models achieve significantly better accuracy than fluid models while maintainingsimilar numerical efficiency. HyQMOM proves particularly robust across all tested conditions, accurately reconstructing velocity distribution functions in both plasma bulk and sheath regions.Realistic ion–neutral collisions, including isotropics cattering and charge exchange, are then introduced using real argon cross-section data. In particular, wedeveloped a particular collision model for HyQMOM,further improving results fidelity.Finally, electron dynamics is studied using an isotropic moment formulation based on the spherical harmonics expansion. Implemented in a 0D simulation, this modeling effectively represent non-Maxwellian features,especially the ionization.Overall, the method of moments was shown to be apromising and efficient alternative to kinetic models to describe weakly-ionized low-temperature plasma, capable of capturing nonequilibrium effects with reduced computational cost. (10.70675/71a84499zfbbaz4fefza287zf139deee9ba5)
  DOI : 10.70675/71a84499zfbbaz4fefza287zf139deee9ba5
• Establishing a European Heliophysics Community (EHC)
  
  • Nakamura Rumi
  • Dudok de Wit Thierry
  • Jones Geraint H
  • Taylor Matt G G T
  • André Nicolas
  • Goetz Charlotte
  • Hadid Lina Z
  • Hayes Laura A
  • Hietala Heli
  • Jackman Caitríona M
  • Kepko Larry
  • Marchaudon Aurélie
  • Masters Adam
  • Owens Mathew
  • Partamies Noora
  • Poedts Stefaan
  • Rae Jonathan
  • Shprits Yuri
  • Temmer Manuela
  • Verscharen Daniel
  • Wimmer-Schweingruber Robert F
  Annales Geophysicae, European Geosciences Union, 2025, 43 (2), pp.855-879. Europe hosts a large and highly active community of scientists working in the broad domain of Heliophysics. This broad discipline addresses plasmas in the regions of space and atmosphere influenced by the Sun and solar wind. However, this community has historically been fragmented, both geographically and thematically, which has limited the potential for strategic coordination, collaboration, and growth. This has recently prompted a grass-roots community-building effort to foster communication and in-teractions within the European Heliophysics Community (EHC). This white paper outlines the motivation, priorities, and initial steps towards establishing the EHC, and presents a vision for the future of Heliophysics in Europe. As a crucial first step of this endeavour, a dedicated EHC website is now available: https://www.heliophysics. (10.5194/angeo-43-855-2025)
  DOI : 10.5194/angeo-43-855-2025
• Fundamental mechanisms of plasma-surface interaction : application to plasma-membrane coupling for CO2 recycling
  
  • Sadi Dihya
  , 2025. CO2 valorization processes aims to use CO2 from industrial emissions as a feedstock rather than treating it as waste. To achieve this, it is necessary to chemically convert CO2 at low energy cost despite the intrinsic stability of this molecule. Cold plasmas (partially ionized gases), being non-equilibrium media, enable efficient transfer of energy into molecular vibrations while maintaining a low gas temperature. This property allows CO2 to become chemically reactive and form high energy-density molecules (ethanol, methanol, etc.). However, a major challenge of most plasma-assisted chemical synthesis processes lies in controlling product selectivity. In particular, in CO2 plasmas it is difficult to prevent back-reactions reforming CO2 from CO and O or O2. This thesis work proposes a solution to this issue by placing ceramic ionic membranes directly in contact with the plasma to continuously extract the oxygen atoms formed. In doing so, reverse reactions are inhibited and the energy efficiency of CO2 conversion is significantly enhanced.To implement this approach, two scientific questions are central: (1) the impact of surfaces on the vibrational kinetics of CO2, and (2) conversely, the influence of the plasma on surface reactivity and transport mechanisms. A joint understanding of both the gas phase and the surface is therefore required. For this purpose, extit{in-situ} surface spectroscopies (IR and Raman), combined with conventional (FTIR, OES) and novel (FC) spatially and spectrally resolved diagnostics of the gas phase, will be employed to elucidate the fundamental mechanisms of plasma-material interactions. Finally, the feasibility of a plasma-membrane system will be demonstrated, and its performance assessed in light of these fundamental results. (10.70675/ebbdd718zfdc9z4ea3z9fe6z416ddbdf493d)
  DOI : 10.70675/ebbdd718zfdc9z4ea3z9fe6z416ddbdf493d
• Fiche n° 129 : Affinités électroniques atomiques : découverte d’un biais négligé dans les dernières mesures classiques
  
  • Blondel Christophe
  • Drag Cyril
  L'Actualité Chimique, Société chimique de France (SCF), 2025, 508-509, pp.109-110. L'affinité électronique d'un atome est, par définition, la différence d'énergie entre le système constitué de cet atome A et d'un électron libre e- séparés et le système constitué par leur réunion sous forme d'un ion négatif A-. Contrairement à ce que peut suggérer l'intuition, l'existence d'un ion négatif stable n'est pas le privilège rare de quelques atomes particulièrement électronégatifs - typiquement les halogènes - mais, au contraire, une propriété partagée par le plus grand nombre. Même les alcalins, plus connus pour la facilité avec laquelle on peut leur soustraire un électron, sont aussi capables d'en attacher un. À l'ion négatif stable ainsi formé, il faudra fournir une énergie positive, l'affinité électronique, pour à nouveau détacher - c'est le mot consacré - cet électron supplémentaire. La connaissance des affinités électroniques est donc une nécessité très fréquente pour la modélisation des réactions atomiques et moléculaires. (10.63133/scf.act-chim.2025.508.11)
  DOI : 10.63133/scf.act-chim.2025.508.11
• Nanosecond discharges as a tool for measuring energy efficiency ( G -values) at high reduced electric fields based on nitrogen dissociation
  
  • Orel Inna S
  • Haouchat Youssef
  • Chng Tat Loon
  • Popov Nikolay
  • Starikovskaia Svetlana M
  Plasma Sources Science and Technology, IOP Publishing, 2025, 34 (11), pp.115014. The production of reactive species in nanosecond, repetitively pulsed plasmas is of decisive importance in tailoring such discharges to different applications. In this paper, we examine the features and advantages of using a nanosecond discharge at moderate pressure as a tool for measuring the G -value. The N-atom production in a pure N 2 , nanosecond pulsed plasma at a moderate pressure of 20 mbar and high reduced electric field of 180 ± 20 Td is adopted as the test case. The atomic nitrogen density is measured using two-photon absorption laser-induced fluorescence (TALIF). A principal objective of this work is to compare the resulting G -value with those of other authors at lower electric fields and with our previous paper measuring G -values at the same reduced electric fields but higher specific energy deposition (SED). The spatially non-uniform profile of plasma in the present work, which displays a minimum at the center, necessitates the conception and implementation of an in-house, Abel inversion algorithm to accurately reconstruct the radial profile. This in turn permits a more accurate determination of the nitrogen dissociation in the entire tube, thereby achieving good agreement with kinetic simulations. Taken together, these results conclusively demonstrate the advantages of using pulsed nanosecond discharges at moderate pressures for studying the energy efficiency of dissociation processes at high E/N . (10.1088/1361-6595/ae163a)
  DOI : 10.1088/1361-6595/ae163a
• Experimental Study of Atmospheric Pressure Plasma Jets : Electric Fields, Discharge Mechanisms, and Biological Effects
  
  • Saugé Louis
  , 2025. Atmospheric pressure plasma jets (APPJs) are attracting growing interest due to their multiple applications, particularly in the biomedical field. In wound healing, most research in plasma medicine attributes their positive effects on biological targets to reactive oxygen and nitrogen species (RONS) and overlooks other plasma components such as UV radiation, metastable species, or electric fields. The aim of this thesis is to demonstrate the importance of studying the electric fields emitted by the plasma in order to better understand the physics of the associated discharges. Few studies in the literature compare different experimental devices in terms of electrode configuration or reactor geometry. This study examines and compare several configurations by using different high voltage sources (pulsed DC or kHz AC) as well as different reactor geometries (linear reactor, diffusive reactor) and electrode configurations (pin, pin-ring, ring, ring-ring). To do this, several diagnostics are used, including the Pockels effect electric field probe, and intensified high speed camera.These different configurations are then studied when the plasmas interact or not with a dielectric target, before studying the quantities of species transferred to aqueous targets. Finally, the biological impact associated with these configurations is compared, highlighting that electric fields are an essential component in the wound healing process. (10.70675/2e11e2edza021z4cf3z8c2azdc16f8163032)
  DOI : 10.70675/2e11e2edza021z4cf3z8c2azdc16f8163032
• Determination of the accuracy of actinometry and line ratio techniques in an O 2 glow discharge: part I, comparison of absolute oxygen atom densities with CRDS measurements
  
  • Baratte Edmond
  • Kuijpers Lex
  • Silva Tiago
  • Guerra Vasco
  • van de Sanden M C M
  • Booth Jean-Paul J-P
  • Guaitella Olivier
  Plasma Sources Science and Technology, IOP Publishing, 2025. The accuracy of oxygen atom density measurements in plasmas by optical emission actinometry was tested by comparison to simultaneous direct absorption measurements on the 1 D 2 -> 3 P 2 transition by cavity ringdown spectroscopy (CRDS). The accuracy of the latter technique depends only on the accuracy to which the transition probability is known. Measurements were performed on a glow discharge in O 2 operating between 0.5 and 5 Torr, and using both Ar and Xe as the actinometer gas. The rate constants for electron impact excitation, and thus the actinometry calibration factors, were calculated from the (measured) reduced electric field using a Boltzmann equation solver (Loki-B). Several sets of cross-section were tested for the EEDF calculation and for the electron impact excitation to the specific levels of O, Ar and Xe used for actinometry. The best results were obtained with the IST Lisbon cross-section set for O 2 and O, and the BSR500 excitation cross-sections for Ar and Xe. Good agreement with the CRDS trends and absolute values was observed when using Xe as the actinometer gas, whereas with Ar the trends were well reproduced but it was necessary to increase the electron impact cross-section of the transition Ar( 1 S 0-> 2p 1 ) of the BSR500 database by a factor of 3˘0.3 to reproduce the absolute values. (10.1088/1361-)
  DOI : 10.1088/1361-
• Determination of the accuracy of actinometry and line ratio techniques in an O ₂ glow discharge: part II, Electric field measurements with Ar and Xe admixtures
  
  • Kuijpers Lex
  • Baratte Edmond
  • Guaitella Olivier
  • Booth Jean-Paul
  • Guerra Vasco
  • van de Sanden Richard
  • Silva Tiago
  Plasma Sources Science and Technology, IOP Publishing, 2025. A line-ratio method for determining the reduced electric field is benchmarked against independent measurements from electrostatic probes and cavity ring-down spectroscopy (CRDS). The method is applied to oxygen DC glow discharges with trace admixtures of argon and xenon. A corona model incorporating fluorescence quenching by heavy species is used to simulate the emission, with electron-impact excitation rates calculated using the LisbOn KInetics Boltzmann solver (LoKI-B). The excitation cross sections and quenching coefficients are those proposed and validated for actinometry in part one of this combined study [1]. The reduced electric field is determined over a pressure range of 0.55 to 5 Torr (at 40 mA) and a current range of 15 to 50 mA (at 5 Torr). Consistent agreement with measured emission line intensities is achieved when applying a correction factor of κ c,Ar = 3 ± 0.5 to the excitation cross sections for the argon lines at 750 nm and 811 nm. With this correction, the reduced electric field values obtained from the line-ratio method are in good agreement with direct measurements. A comparison of different line ratios is presented, showing that the best performance is achieved using the ratio of the Ar 750 nm and Xe 828 nm lines. This ratio is particularly sensitive to changes in the electron energy distribution function, due to the large difference in excitation thresholds, while remaining independent of the knowledge of species densities. (10.1088/1361-6595/ae24aa)
  DOI : 10.1088/1361-6595/ae24aa
• Plasma froid à pression atmosphérique : Rôle du champ électrique sur la migration cellulaireEt étude d’un jet diffusif sur des marqueurs de la cicatrisation
  
  • Laberie Benjamin
  , 2025. La médecine du plasma est un jeune domaine qui est très prometteur, notamment pour la cicatrisation des plaies et des brûlures. Le plasma froid à pression atmosphérique (CAP) aide la cicatrisation de ces plaies très problématiques. Cet effet n’est plus à démontrer : de nombreux essais cliniques s’accordent sur les effets bénéfiques du CAP sur la cicatrisation. Cependant, les causes ne sont que partiellement comprises.La cicatrisation est un phénomène très complexe composé de plusieurs phases. L’effet du CAP, sur les différentes phases de la cicatrisation, est bien documenté.Néanmoins, si des études mettent en évidences l’impact du CAP sur les différents aspects de la cicatrisation, les mécanismes fondamentaux aux niveaux cellulaire et moléculaire sont bien moins compris. Cette thèse aborde certains mécanismes impliqués dans l’effet bénéfique du CAP et le développement d’un nouveau dispositif plasma.Premièrement, nous avons exploré l’effet du plasma froid sur la migration mésenchyme des fibroblastes primaires humains et la mécanistique moléculaire sous-jacente. Puis, l’effet de deux constituants principaux produit par le CAP, le champ électrique d’une part, certaines espèces réactives de l’oxygène et de l’azote de l’autre a été analysé.Il en résulte que la migration individuelle devient plus efficace à travers une stimulation de l’activité de Arp2/3 et que la synergie entre les espèces réactive de l’oxygène et le champ électrique produit par le plasma est responsable de ce phénomène.Deuxièmement, nous avons mis en place un dispositif plasma innovant utilisant du verre frité, nommé configuration diffusive. Puis, nous avons comparé ce dispositif à des dispositifs déjà bien connus. Cette comparaison a été faite sur le plan physique, chimique et biologique. La configuration diffusive induit un champ électrique intense, produit très peu d’espèce chimique et augmente la sécrétion de collagène sans induire d’effet négative aux cellules. Les configurations standards montrent un champ électrique moins intense, produisent en plus grande quantité d’espèces chimiques et augmentent la prolifération cellulaire, mais induisent un effet négatif lors de long traitement.Ensemble, ces résultats démontrent que l’effet bénéfique du plasma froid repose sur une synergie entre le champ électrique et les espèces réactives de l’oxygène, et ouvrent la voie à la conception de nouveau dispositif plasma pour optimiser le traitement des plaies. (10.70675/37b155c9z30abz401fz88faz7c1ab6056c6b)
  DOI : 10.70675/37b155c9z30abz401fz88faz7c1ab6056c6b
• Mercury's Altered Magnetosphere During a Sub‐Alfvénic ICME Event: MESSENGER Observations and Inferred Asymmetric Alfvén Wing Formation From Global MHD Simulations
  
  • Bowers Charles
  • Jackman Caitríona
  • Jia Xianzhe
  • Hadid L. Z.
  • Sun Weijie
  • Hayes Laura
  • Dewey Ryan
  • Burkholder Brandon
  • Hollman Daragh
  • Cervantes Sebastian
  • Huybrighs Hans
  • Rutala Matthew
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2025, 130 (11), pp.e2025JA034248. We present observations of a rare configuration of Mercury's magnetosphere in response to sub‐Alfvénic upstream conditions, driven by an interplanetary coronal mass ejection (ICME) that impacted the planet on 1 May 2013. Using data from the Mercury Surface, Space Environment, Geochemistry, and Ranging (MESSENGER) spacecraft, supported by a global three‐dimensional magnetohydrodynamic (MHD) simulation of the event, we demonstrate that Mercury's magnetospheric response during this interval was distinct from the typical super‐Alfvénic state. During the sub‐Alfvénic upstream conditions, MESSENGER measured a distorted magnetotail with a depleted southern magnetotail lobe. An MHD simulation closely reproduces these observations, providing a plausible global context for the reconfiguration of Mercury's magnetosphere under sub‐Alfvénic conditions. The simulation predicts that a pair of Alfvén wings formed during this event, redirecting magnetic flux and plasma within the magnetosphere. The interplanetary magnetic field orientation during this event was primarily sunward/dawnward, generating asymmetric Alfvén wings with respect to the flow direction, in contrast to previously observed north–south wing configurations at the planet. Using Solar Orbiter observations in the inner heliosphere, we estimate that the solar wind is sub‐Alfvénic approximately 2.5 times per Earth year near solar maximum, with intervals lasting between 10 s and 12 hr. Studies of these rare, sub‐Alfvénic solar wind‐magnetospheric interactions provide valuable insights into exoplanet–stellar wind interactions under similarly sub‐Alfvénic conditions where in situ observations are not available. (10.1029/2025JA034248)
  DOI : 10.1029/2025JA034248
• Cassini CAPS‐ELS Observations of Low‐Energy Electron Beams Within Enceladus Mid‐Latitude Flux Tubes
  
  • Rabia J.
  • Hadid L.
  • André N.
  • Nénon Quentin
  • Chust T.
  • Pisa D.
  • Parsec-Wallis A.
  • Coates A.
  • Rymer A.
  Geophysical Research Letters, American Geophysical Union, 2025, 52 (22). Abstract The electrodynamic interaction between Saturn's magnetosphere and Enceladus accelerates electrons along magnetic field lines. These electrons propagate inside magnetic flux tubes connecting the moon to the giant planet, generating distinctive auroral hiss and auroral footprint signatures, both previously observed by the Cassini spacecraft. In this study, we analyze low‐energy electron measurements made during multiple mid‐latitude crossings of magnetic flux tubes connected to Enceladus' wake. We show that the properties of the observed electrons are consistent with those of electrons inducing Enceladus' auroral hiss, and discuss the physical processes responsible for their pitch‐angle distributions and acceleration. Field‐aligned electron beams have very different properties from those triggering the Enceladus ultraviolet footprint, with a much lower characteristic energy and energy flux. Observations of electron beams resulting from the moon‐magnetosphere interactions up to 30° downstream of the moon reveal that the coupling system between Enceladus and Saturn is significantly more extended than previously anticipated. (10.1029/2025GL119448)
  DOI : 10.1029/2025GL119448
• Edge radial electric field in positive and negative triangularity plasmas in the TCV tokamak
  
  • Rienäcker S.
  • Hennequin P.
  • Vermare L.
  • Honoré C.
  • Bouffet-Klein R.
  • Coda S.
  • Labit B.
  • Vincent B.
  • Thome K.E.
  • Krutkin O.
  • Balestri A.
  • Nakeva Y.
  Nuclear Fusion, IOP Publishing, 2025, 66 (1), pp.014002. Abstract We present the first edge Er measurements in negative triangularity (NT) plasmas in the Tokamak à Configuration Variable (TCV). The Doppler backscattering measurements of v⊥ ≈ Er / B reveal a significant impact of triangularity on the Er well: in Ohmic, neutral beam injection, and electron cyclotron resonance heated discharges, the Er well and associated Er × B shear are stronger in NT-shaped plasmas compared to their positive triangularity (PT) counterpart. This suggests a connection to the concomitant NT performance gain relative to PT L-mode. (10.1088/1741-4326/ae19fd)
  DOI : 10.1088/1741-4326/ae19fd
• A Compact Ion‐Electron Plasma Camera Spectrometer With an Instantaneous Hemispheric Field of View
  
  • Hénaff Gwendal
  • Berthomier Matthieu
  • Leblanc Frédéric
  • Techer Jean‐denis
  • Alata Yvan
  • Costa Carla
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2025, 130 (11). Using additive manufacturing and a selective metalization technique, we have developed a compact ion/electron plasma camera based on the donut topology. With its instantaneous field of view of , it eliminates the need for electrostatic deflectors. This 17 cm diameter plasma camera has an energy range from a few eV to 22 keV, an energy resolution of and a geometric factor of per pixel, with 64 pixels corresponding to as many individual directions of observation. We have characterized its experimental response under an electron beam and compared it with numerical simulations. We have shown how carbon foils can be used as conversion layers to sequentially measure ions and electrons with a set of micro‐channel plates biased at a fixed voltage. This principle was tested under electron and ion beams. (10.1029/2025JA034516)
  DOI : 10.1029/2025JA034516
• Modeling Jovian Plasma‐Europa Interactions: Innovative Atmosphere and Ionosphere Depiction for JUICE Mission Insights
  
  • Baskevitch Claire
  • Modolo Ronan
  • Cecconi B.
  • Leblanc François
  • Aizawa Sae
  • Oza A.
  • Walhund J.-E.
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2025, 130 (11), pp.e2025JA033740. The JUpiter ICy moons Explorer (JUICE) mission, launched by the European Space Agency (ESA) in April 2023, aims to explore Jupiter and its icy moons, particularly focusing on Europa, Ganymede, and Callisto. This study uses the Latmos Hybrid Simulation (LatHyS) model to simulate Europa's plasma and field environment, emphasizing the upcoming JUICE flybys in July 2032. The LatHyS model, incorporating a detailed 3D exospheric model and a self‐consistent ionosphere, allows for comprehensive analysis of the moon‐plasma interactions at ion scales. Our simulations, validated against Galileo's E4 flyby data, demonstrate the model's accuracy in reproducing key features of the plasma environment and ionospheric dynamics. To characterize the system's response to neutral/ionospheric environment assumptions, we compare three simulations, with different neutral and ionosphere impacts, revealing the ionosphere's influence on the magnetic field intensity. Using an atmosphere derived from a planetary exosphere simulation model like EGM allows for the consideration of various asymmetries and multiple major neutral species, supporting further studies on ionospheric ion dynamics. Results highlight the complex interactions influenced by Europa's neutral and ionospheric conditions, providing insights for the anticipated JUICE observations. The measured signatures primarily depend on the interactions with the ionosphere along the spacecraft's trajectory and simulations show that a dense ionosphere deduced from radio occultation observations cannot reproduce the observed in situ signatures. The exosphere being a source for planetary ions, it was shown that it is significant to consider the spatial asymmetries in global interaction models in order to better account for its impact on the system. (10.1029/2025JA033740)
  DOI : 10.1029/2025JA033740
• Gravitational wave turbulence : multi-scale methods and numerical simulations
  
  • Gay Benoît
  , 2025. The first direct detection of gravitational waves by the LIGO-VIRGO collaboration [Abbott et al., 2016], made a century after Einstein's prediction, has opened the door to probing events in the early universe, where many models anticipate the presence of such waves. With their comparatively large amplitudes, these waves can interact in a nonlinear way, offering a new avenue for exploring phenomena arising from general relativity. An analytical theory of weak gravitational wave turbulence [Galtier & Nazarenko, 2017] predicted a dual cascade of energy and wave action that was later borne out through numerical simulations [Galtier & Nazarenko, 2021].In the first part, the kinetic equation governing gravitational wave turbulence is derived using a multi-time-scale approach. The aim is to clarify the role of the initial conditions and to demonstrate the emergence of an analytical closure for four-wave interactions. Although the resulting equation differs slightly from the Hamiltonian formulation, both yield the same Kolmogorov-Zakharov spectrum. We further demonstrate that the system retains a memory of its initial state up to second order in time.This analytical study is then complemented by GPU-accelerated pseudo-spectral simulations, which allow for a more detailed examination of the dynamics of the dual cascade. In particular, the simulations confirm the theoretical predictions and also reveal the existence of intermittent and multifractal behaviour for large amplitude events. The metric components likewise exhibit evidence of a dual cascade, while the scalars of general relativity (Ricci and Kretschmann) point towards a physical relevance.Finally, we turn to the nonlinear diffusion equation derived from the kinetic equation. In the forced regime, we observe a dual cascade consistent with the theoretical Kolmogorov-Zakharov spectra. By contrast, in the decaying case, the wave action spectrum is unexpected: extending beyond the injection scale, leaving only a single inertial range in which the Kolmogorov-Zakharov spectrum gradually develops.Taken together, these studies deepen our understanding of the turbulent behaviour of gravitational waves from both theoretical and numerical standpoints, and represent a step towards a comprehensive theory of gravitational wave turbulence. (10.70675/0d9d45aeza7cdz4453z9110z7e8c9572fea5)
  DOI : 10.70675/0d9d45aeza7cdz4453z9110z7e8c9572fea5
• In-situ quantitative measurements of methyl radicals in oxygen-containing reactive environments by VUV absorption spectroscopy using synchrotron radiation
  
  • Budde Maik
  • Sadi Dihya
  • de Oliveira Nelson
  • Bois Sophie
  • Tardat Mathéo
  • Garcia-Soto Carolina
  • Curley Garrett
  • Baratte Edmond
  • Guaitella Olivier
  Chemical Physics Letters, Elsevier, 2025, 879, pp.142388. Absolute methyl radical number densities are measured in-situ in a low-temperature discharge in methane and oxygen diluted in argon/helium, using vacuum ultraviolet synchrotron radiation absorption spectroscopy. Instead of the methyl absorption band around 216 nm, the exploitation of the more sensitive band at 150 nm is demonstrated. Densities as low as (1.6 ± 0.2) × 1013 cm-2 are detected. With oxygen admixture, the expected monotonous decrease of CH3 density is not observed, but a distinct maximum at a few percent of oxygen, separating a regime dominated by the electron kinetics for low percentages from an oxidation-dominated regime at higher admixtures. (10.1016/j.cplett.2025.142388)
  DOI : 10.1016/j.cplett.2025.142388
• Significant Amplification of Turbulent Energy Dissipation Through the Shock Transition at Mars
  
  • Jiang Wence
  • Li Hui
  • Andrés Nahuel
  • Hadid L. Z.
  • Verscharen Daniel
  • Wang Chi
  Geophysical Research Letters, American Geophysical Union, 2025, 52 (21), pp.e2025GL117801. Turbulence is fundamental to energy transfer across scales in space and astrophysical plasmas. Bow shock interactions have long been hypothesized to significantly modify turbulence in planetary environments, yet the quantification of such effects and their parametric dependencies remain largely unaddressed. Using in situ long‐term high‐time resolution measurements from NASA's MAVEN mission, we report the first observational characterization of the evolution and parametric dependence of the turbulence energy cascade rate at magnetohydrodynamic (MHD) scales. Key findings reveal an averaged three‐order‐of‐magnitude enhancement in when transitioning from the solar wind to the magnetosheath. Notably, downstream measurements of oblique and quasi‐perpendicular shocks exhibit higher energy dissipation rates than those of quasi‐parallel configurations. These results provide the first direct evidence linking shock obliquity to turbulence amplification, offering key insights into shock‐mediated turbulence in similar but inaccessible systems. (10.1029/2025GL117801)
  DOI : 10.1029/2025GL117801
• Flux-driven turbulent transport using penalisation in the Hasegawa-Wakatani system
  
  • Guillon Pierre
  • Gürcan Özgür
  • Dif-Pradalier Guilhem
  • Sarazin Yanick
  • Fedorczak Nicolas
  Journal of Plasma Physics, Cambridge University Press (CUP), 2025, 91 (5), pp.E145. First numerical results from the newly developed pseudo-spectral code P-FLARE (Penalised FLux-driven Algorithm for REduced models) are presented. This flux-driven turbulence/transport code uses a pseudo-spectral formulation with the penalisation method to impose radial boundary conditions. Its concise, flexible structure allows implementing various quasi-two-dimensional reduced fluid models in flux-driven formulation. Here, results from simulations of the modified Hasegawa–Wakatani system are discussed, where particle transport and zonal flow formation, together with profile relaxation, are studied. It is shown that coupled spreading/profile relaxation that one obtains for this system is consistent with a simple one-dimensional model of coupled spreading/transport equations. Then, the effect of a particle source is investigated, which results in the observation of sandpile-like critical behaviour. The model displays profile stiffness for certain parameters, with very different input fluxes resulting in very similar mean density gradients. This is due to different zonal flow levels around the critical value for the control parameter (i.e. the ratio of the adiabaticity parameter to the mean gradient) and the existence for this system of a hysteresis loop for the transition from two-dimensional turbulence to a zonal flow dominated state. (10.1017/S0022377825100895)
  DOI : 10.1017/S0022377825100895
• Automated Nanosecond Plasma Jets for Targeted Medical Treatments
  
  • Billeau Jean-Baptiste
  • Radu Vlad-Ștefănuț
  • Frédéric Gerome
  • Benabid Fetah
  • Polprasarn Kasidapa
  • Pai David Z
  • Seletskiy Dennis
  • Reuter Stephan
  • Starikovskaia Svetlana
  , 2025. Cold atmospheric plasma (CAP) has emerged as a transformative tool in medicine, with applications ranging from selective cancer cell inactivation to the acceleration of wound healing. The therapeutic effects of CAP are largely mediated by reactive oxygen and nitrogen species (ROS/RNS), whose precise composition and concentration must be tightly controlled for safe and effective treatment. However, in many current systems, human handling introduces variability that compromises treatment reproducibility and limit accurate estimation of introduction of reactive species onto a treated surface. This study addresses the need for standardization in plasma-based therapies by implementing a modified computer numerical control (CNC) plasma treatment platform to automate and precisely control exposure parameters. By removing human variability, this system enables reproducible treatment conditions across multiple experimental sessions. To better understand the chemistry at the point of application, preliminary diagnostics were performed using fiber-enhanced spontaneous Raman backscattering. Our preliminary results suggest that reactive species profiles can be accurately defined along with the plasma plume with minimal invasiveness. Furthermore, the use of hollow core fiber allows for significant enhanced signalling effects due to its ability to increase the interaction length between the probing light source and the gas sample. As such, this work lays the groundwork for developing standardized plasma treatment protocols supported by real-time diagnostics. Ongoing and future studies will focus on integrating more advanced optical techniques and correlating plasma chemistry with biological effects to further improve the reliability and effectiveness of plasma-based medical interventions.
• The X-Point Radiator regime in the WEST tokamak for divertor operation in next step fusion devices
  
  • Rivals N
  • Fedorczak N
  • Geulin E
  • Nouailletas R
  • Moiraf D
  • Yang H
  • 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
  • Lunt T
  • Henderson S
  • Reimerdes H
  • Tsitrone E
  • Vianello N
  , 2025.
• Comparison of high-order moment models for the ion dynamics in a bounded low-temperature plasma
  
  • Berger Anatole
  • Lequette N.
  • Magin Thierry E.
  • Bourdon Anne
  • Alvarez Laguna A.
  Physics of Plasmas, American Institute of Physics, 2025, 32 (10). Low-temperature plasmas often present non-equilibrium ion distribution functions due to the collisions with the background gas and the presence of strong electric fields. This non-equilibrium is beyond classical fluid models, often requiring computationally-intensive kinetic simulations. In our work, we study high-order moment models in order to capture the non-equilibrium state with a macroscopic set of equations, which is more computationally efficient than kinetic simulations. We compare numerical simulations of different moment closures: Grad's closure, the hyperbolic quadrature method of moments, the extended quadrature method of moments, and a method based on entropy maximization. We assess the different closures for plasma applications and propose efficient numerical discretizations. The numerical solution of the high-order moment models is compared to kinetic simulations of an argon plasma between two floating walls at different pressure regimes, from nearly collisionless to collisionally-dominated. In general, all the high-order moment closures capture the ion transport with high fidelity as compared to the kinetic simulations, providing an improvement as compared to classical fluid models. Classical fluid closures such as the Fourier law for the heat flux is shown be not suitable to capture the sheath or the low pressure regime. In addition, the ability of each moment method to reconstruct the velocity distribution function from the moments is assessed. The high-order moment models are able to capture the non-equilibrium distributions in the bulk and sheath with remarkable fidelity, dramatically improving classical fluid models while having comparable computational cost. In particular, the hyperbolic quadrature method of moments shows to be a robust method that provides an excellent comparison with the kinetic simulations of both the moments and the distribution function in the bulk and the sheath. (10.1063/5.0281989)
  DOI : 10.1063/5.0281989
• He + ions in the vicinity of mercury observed by the MESSENGER and BepiColombo spacecraft
  
  • Fränz Markus
  • Krüger Harald
  • Raines Jim
  • Glass Austin
  • Gershman Daniel
  • Prencipe Fabio
  • Krupp Norbert
  • Hadid Lina
  • Delcourt Dominique
  • Aizawa Sae
  • Yokota Shoichiro
  • Harada Yuki
  • Saito Yoshifumi
  Planetary and Space Science, Elsevier, 2025, 265, pp.106152. (10.1016/j.pss.2025.106152)
  DOI : 10.1016/j.pss.2025.106152
• Absolute calibration and quantification of atomic oxygen in nanosecond plasmas using two-photon absorption laser-induced fluorescence
  
  • Shu Zhan
  , 2025. Atomic oxygen is commonly generated in reactive media, such as low-temperature plasmas and combustion environment. Owing to its high chemical reactivity and consequent short lifetime, time- and space-resolved measurements of O-atom density are essential for elucidating particle kinetic behavior and reaction mechanisms. Two-photon absorption laser-induced fluorescence (TALIF) has emerged as a powerful non-intrusive technique for detecting atomic species. By employing fast (nanosecond) and ultra-fast (picosecond or femtosecond) laser pulses, this technique enables the excitation of ground-state atoms and the detection of their subsequent fluorescence, offering excellent temporal and spatial resolution. When properly calibrated, TALIF allows absolute quantification over a dynamic range.A significant challenge in the calibration of O-TALIF lies in the uncertainty associated with the two-photon absorption cross-section ratio between the reference gas xenon and atomic oxygen. This ratio was determined by only one group of authors and has been widely used for twenty years. However, recent studies have indicated that this value may lead to an overestimation of the atomic oxygen density. Another issue happens when applying ultra-fast TALIF, which is especially well-suited for diagnosing transient plasmas characterized by strong collisional quenching at high pressures. Under conditions of high laser power density, the rate-equation-based model may overestimate the excited-state population, and thus the inferred ground-state density, due to the omission of coherence effects and saturation phenomena.This thesis proposed a novel approach to calibrate the two-photon absorption cross-section ratio of Xe/O in nanosecond TALIF application. A nanosecond pulsed discharge, applied within a millimeter-scale capillary tube, enables efficient molecular dissociation at high reduced electric field and high specific deposited energy. Notably, complete dissociation of molecular oxygen was achieved in the afterglow of a N2+5%/2% O2 discharge at moderate pressure, providing a practical and well-characterized source of atomic oxygen. Then the known density served as a robust calibration reference for the Xe/O cross-section ratio. A developed one-dimensional numerical simulation was used to verify the 100% oxygen dissociation, compare with the experimental data, and analyze the formation pathways of atomic oxygen. Electrical diagnostics were employed by back-current shunt and capacitive probe techniques, while gas temperature was determined using optical emission spectroscopy. These measurements helped to characterize and customize the discharge, forming the basis for kinetic modeling and the validation of calculation results.The calibration work of Xe/O cross-section ratio was subsequently extended to picosecond TALIF measurements. Compared to nanosecond TALIF, the picosecond pulsed laser offers a more efficient excitation of ground-state oxygen atoms. The Xe/O cross-section ratio was confirmed to be 1.8 for both nanosecond and picosecond regimes, with uncertainties of ±0.2 and ±0.3, respectively. The validity range of the rate equations and the conditions under which a transition to the optical Bloch equations becomes necessary were discussed.Further applications of O-TALIF were explored, emphasizing its capability for time- and space-resolved diagnostics. The temporal evolution of atomic oxygen in the afterglow of nanosecond capillary discharges in CO2 was measured to validate the kinetic model and provide insights into the dissociation pathways at high reduced electric field and high specific deposited energy. The implementation of absolute calibration in the nanosecond varying-gap plane-to-plane discharge confirmed the formation of an O-atom density gradient, which may play a critical role in the initiation and propagation of detonation waves. (10.70675/8cb96554zb67cz4400z94eaz49620a743032)
  DOI : 10.70675/8cb96554zb67cz4400z94eaz49620a743032
• 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
  The Journal of physical chemistry, American Chemical Society (ACS), 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. (10.1021/acs.jpcc.5c02224)
  DOI : 10.1021/acs.jpcc.5c02224