Publications

2025

• 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
• 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.
• 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. (10.48550/arXiv.2505.10456)
  DOI : 10.48550/arXiv.2505.10456
• 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
• Comparing PIC/MCC Simulations and Experimental Data for the PPS ® X00-ML Hall Thruster IEPC
  
  • Petronio Federico
  • Laguna Alejandro Alvarez
  • Bourdon Anne
  • Chabert Pascal
  • Laurent Benjamin
  , 2025. <div><p>Validating simulation results against experimental measurements of Hall thruster (HT) performance has long been a major challenge. Few examples of successful comparison do exist in the literature. In this work, we compare the results of three codes: (1) fluid stationary, (2) fluid non-stationary, and (3) two dimensional Particle-in-Cell/Monte Carlo-Collisions (PIC/MCC), with experimental measurements on the Laboratory Model (ML) thruster PPS ® X00-ML HT by Safran Spacecraft Propulsion. The results show that fluid and PIC/MCC simulations can successfully reproduce some macroscopic measured quantities, such as discharge current, thrust, and specific impulse. Simulations also offer the possibility to inquire the state of the plasma inside the thruster, gaining a deeper insight on the plasma characteristics along the thruster axis.</p></div>
• Convolutions on partially regular recurrent lattices
  
  • Gürcan Ö.D.
  • Manfredini L.
  Communications in Nonlinear Science and Numerical Simulation, Elsevier, 2025, 152, pp.109262. Partially regular recurrent lattices, are k-space grids that we propose, which consist of a central regular region that is extended using a recurrence relation, resulting in an asymptotically logarithmic lattice structure. Such a lattice can be used to model the turbulent cascade over a very large range of scales covered by the recurrent part, while keeping the large scale eddies mainly in the regular part. Here we propose a novel pseudo-spectral algorithm for computing the convolutions over such a lattice, using an overlapping partition of its different parts, using the fact that the interactions in the recurrent part of the lattice are limited, in each direction, to a small number of elements linked through the recurrence relation. We compare the results with a full grid, dense, fast Fourier transform (fft) based convolution, where the nonexistent elements on the full grid are set to zero, and show that the difference remains within a few orders of the machine precision. The algorithm in two dimensions uses one fft for the regular grid, and bunch of smaller ffts for the rest of the points, either elongated to match the length of the regular part of the grid in one dimension or even smaller ffts (typically) to include the interactions between recurrent parts of the lattice. The algorithm can be trivially generalized to arbitrary number of dimensions. (10.1016/j.cnsns.2025.109262)
  DOI : 10.1016/j.cnsns.2025.109262
• Influence of chemical and morphological properties on the mid-infrared refractive indices of Titan aerosol analogs
  
  • Perrin Zoé
  • Drant Thomas
  • Garcia-Caurel Enrique
  • Brubach Jean-Blaise
  • Ruscassier Nathalie
  • Gautier Thomas
  • Sciamma-O’brien Ella
  • Vettier Ludovic
  • Chatain Audrey
  • Guaitella Olivier
  • Carrasco Nathalie
  , 2025. In the atmosphere of Saturn's largest satellite, Titan, the solid particles in suspension (photochemistry organic aerosols) play an important role notably to the attenuation of the solar spectrum by absorption and scattering. To constrain these interactions, the optical properties of Titan’s atmospheric aerosols, refractive index n and extinction coefficient k were recovered from observations [1, 2, 3, 4]. The refractive indices database has been expanded using solid analogs of Titan's aerosols produced and analyzed in laboratory [5, 6, 7]. The experimental data are generally consistent with the optical properties derived from Titan’s aerosols, including the contribution to the extinction and albedo of Saturn's moon [5, 7, 8]. However, comparisons of vibrational modes in the mid-infrared (MIR) suggest a difference in composition between laboratory analogs and Titan’s aerosols [9, 10]. These discrepancies in the refractive indices of solids can originate from their morphological and chemical properties. Indeed, numerous experimental studies have revealed the variability in the morphology and chemical composition of solid analogs formed in simulations of Titan's atmospheric chemistry. (10.5194/epsc-dps2025-904)
  DOI : 10.5194/epsc-dps2025-904
• Interhemispheric and Latitudinal Variability of Ionospheric Disturbances During the 19-20 December 2015 Geomagnetic Storm: Insights from the South American Sector
  
  • Afolabi Oladayo O
  • Candido Claudia M.N.
  • Becker-Guedes F.
  • Amory-Mazaudier Christine
  • Fleury Rolland
  Advances in Space Research, Elsevier, 2025. This study investigates the response of the South American ionosphere to the December 19-20, 2015, geomagnetic storm using multi-instrument satellite and ground-based data. An interplanetary shock triggered prompt penetration electric fields (PPEFs) during the storm's initial phase, initiating rapid DP2 currents and significant equatorial electrojet (EEJ) fluctuations, particularly in Jicamarca, Peru. Our analysis shows that dayside field-aligned currents (FACs) are the primary drivers of the observed DP2 fluctuations. The South Atlantic Magnetic Anomaly (SAMA) also induced a westward geomagnetic gradient-induced current at the equatorward boundary, which suppressed the EEJ current at São Luiz during the magnetically quiet period. During the storm's main phase, eastward PPEFs enhanced ionospheric irregularities at several Global Positioning Satellite (GPS) stations: Sao Luiz (14.8%), Cuiaba (11.4%), and Jatai (15.5%) in Brazil; Tucuma (33.6%) and Rio Grande (33.2%) in Argentina; and all Peruvian GPS stations (5.8 -57.6%), with Arequipa showing the highest percentage. Conversely, irregularities were inhibited at Eusebio (-31.5%), São José dos Campos (-11.8%), and Campo Grande (-4.8%) in Brazil, and Rosario (-9.4%) and Villegas (-0.8%) in Argentina, relative to a magnetically quiet day, which was attributed to the interplay between westward disturbance dynamo electric fields (DDEF) and PPEF. Joule heating, peaking at 14:35 UT on 20 December drove equatorward disturbance winds that generated the DDEF and modulated irregularities during the recovery phase. Westward DDEF suppressed post-sunset irregularities across most Brazilian and Argentine stations (-50.2% to -10.1%), but slightly enhanced post-midnight ionospheric irregularities at Cuiabá (+4.3%) and Tucuma (+21.1%). All Peruvian stations recorded post-midnight enhancements (+14.8% to +136.7%), with Arequipa showing the highest increase. We quantified the delayed magnetic response of the disturbance dynamo (Ddyn) relative to Joule heating, revealing propagation delays of approximately 6, 8.5, and 8.2 h in Brazil, Argentina, and Peru, respectively. Ddyn exhibited strong spatiotemporal variability, including spatial anomalies associated with the SAMA. The Peruvian sector dominated the Ddyn power (59.0%), followed by Brazil (35.1%) and Argentina (5.9%). Evidence of interhemispheric FAC asymmetry, attributed to seasonal variability, was also observed. These findings significantly advance our understanding of storm-time lowlatitude electrodynamics and their regional variability. (10.1016/j.asr.2025.09.026)
  DOI : 10.1016/j.asr.2025.09.026
• Polarization Ratios of Turbulent Langmuir/$\mathcal{Z}$ -mode Waves Generated by Electron Beams in Magnetized Solar Wind Plasmas
  
  • Polanco-Rodríguez F J
  • Krafft C.
  • Savoini P.
  The Astrophysical Journal Letters, Bristol : IOP Publishing, 2025, 989 (2), pp.L38. The polarization ratios F = ∣E_⊥∣²/∣E∣² of beam-generated turbulent Langmuir/Z-mode ($\mathcal{LZ}$) waves and electromagnetic emissions radiated at plasma frequency ω_p from such sources are studied in weakly magnetized and randomly inhomogeneous plasmas. Large-scale and long-term 2D/3V particle-in-cell simulations with parameters relevant to type III solar radio bursts are performed. Statistical studies using waveforms recorded by virtual satellites are carried out to determine the distributions of polarization ratios as a function of beam and plasma parameters. This efficient method, which mimics waveform recording by spacecraft in the solar wind, leads to results consistent with observations. Moreover, plasma random density fluctuations δn turn out to be the key factor responsible for the increase in polarization ratios up to F ∼ 1. Indeed, it is demonstrated that linear mode conversion at constant frequency near of ω_p of $\mathcal{LZ}$ waves scattering on δn is the most efficient and fastest process to produce large polarization ratios in randomly inhomogeneous plasmas. This is due to electromagnetic slow extraordinary $\mathcal{Z}$-mode wave emission by $\mathcal{LZ}$ wave turbulence. The results provide guidance to theoretical studies and useful support to estimate the average level of density fluctuations in solar wind plasmas. (10.3847/2041-8213/adf4ce)
  DOI : 10.3847/2041-8213/adf4ce
• A Gyromoment Approach for Electron Dynamics in Low-Temperature E × B Plasmas of Hall Thrusters
  
  • Tazakkati Zoubaïr
  • Laguna Alejandro Alvarez
  • Massot Josselin
  • Massot Marc
  • Pichard Teddy
  , 2025. <div><p>We study the electron dynamics in the acceleration region of a Hall thruster (HT). The strong crossed electric and magnetic fields induce both a fast electron cyclotron gyration around the magnetic field lines and a E × B drift. Starting from a Boltzmann-Poisson system, we perform a dimensional analysis to identify the dominant physical effects within this zone. This yields a non-dimensional kinetic equation tailored to the regime of interest, featuring multiple small parameters and a clear scale separation. The fast cyclotron gyration are filtered out through a Hilbert expansion combined with a gyroaveraging operator, yielding a reduced gyrokinetic model. Then a gyrofluid model is derived using a moment method with an entropy-based closure. Owing to the symmetries introduced by the gyroaveraging process, the number of required moments is reduced, and the closure corresponds to an anisotropic Gaussian requiring only four moments: the density, parallel momentum, and two directional temperatures. A numerical strategy using common tools from the literature is provided to handle the remaining small scales. Numerical experiments exhibit promising results for our applications.</p></div>
• Generation of zonal flows and impact on transport in competing drift waves and interchange turbulence
  
  • Panico Olivier
  • Sarazin Yanick
  • Hennequin Pascale
  • Gürcan Ozgur
  • Dif-Pradalier Guilhe
  • Garbet Xavier
  • Varennes Robin
  Journal of Plasma Physics, Cambridge University Press (CUP), 2025, 91 (4), pp.E118. The generation and radial structure of zonal flows are studied in competing collisional drift waves and interchange turbulence using the reduced flux-driven nonlinear model Tokam1D. Zonal flows are generated in both the interchange dominated and adiabatic regimes with the former favoring radially structured flows and avalanche transport. The distance to the instability threshold proves to be key, with a more stable radial flow structure emerging near the threshold and increased energy stored in the flows for interchange turbulence. The avalanches are shown to perturb zonal flow structures in drift-wave turbulence and to reactivate them in the interchange regime. Finally, the ExB staircases with radially structured, stable in time zonal flows are proved beneficial for the overall confinement. (10.1017/s0022377825100603)
  DOI : 10.1017/s0022377825100603
• Photoelectric Effect in Air Explains Lightning Initiation and Terrestrial Gamma Ray Flashes
  
  • Pasko Victor P
  • Celestin Sebastien
  • Bourdon Anne
  • Janalizadeh Reza
  • Pervez Zaid
  • Jansky Jaroslav
  • Gourbin Pierre
  Journal of Geophysical Research: Atmospheres, American Geophysical Union, 2025, 130 (14). Terrestrial gamma ray flashes (TGFs) are high‐energy photon bursts that have been linked to short bursts of electromagnetic radiation associated with lightning activity. The most puzzling unexplained aspect of these events is that gamma rays originate from very compact regions of space while the source regions often seem to be optically dim and radio silent when compared to processes in ordinary lightning discharges. In this work, we report a mechanism that allows precise quantitative explanation of these peculiar features of TGFs and their relationships to the observed waveform characteristics of associated radio emissions. The mechanism represents an extension of earlier ideas on feedback processes in growth of relativistic runaway electron avalanches (Dwyer, 2003, https://doi.org/10.1029/2003GL017781 ), and is based on a recent demonstration of the dominant role of the photoelectric feedback on compact spatial scales (Pasko, Celestin, et al., 2023, https://doi.org/10.1029/2022GL102710 ). Since discussed events often occur in isolation or precede formation of lightning discharges, the reported findings propose a straightforward solution for the long‐standing problem of lightning initiation. (10.1029/2025JD043897)
  DOI : 10.1029/2025JD043897
• In-situ measurement of surface reaction probabilities in low-pressure plasmas
  
  • Booth Jean-Paul
  • Zhang Shu
  • Curley Garrett
  , 2025. Surface-catalysed recombination is often the dominant loss process for reactive atoms and free radicals created in low-pressure plasmas in molecular gases. However, ab-initio theoretical methods to estimate the rates of these processes are far from mature, in part due to the complexity of the chemical composition and morphology of surfaces subjected to energetic ion bombardment. Therefore, reliable in-situ measurements are essential to understand the chemical kinetics of these systems. A number of experimental techniques to measure surface reaction rates have been developed, and will be reviewed in this talk. However, analysis of these experimental results has historically relied on simplifying assumptions, notably that of constant surface reaction probability, . However, high-quality data from improved experimental techniques combined with systematic measurements in simplified model systems has shown that this assumption is far from correct in many circumstances. More sophisticated surface models are therefore necessary.
• Comparative Study on Microwave Diagnostics: Cutoff Probe, Hairpin Probe, and Microwave Interferometer
  
  • Kim S.
  • Booth Jean-Paul
  • Curley Garrett
  , 2025. We have compared three microwave diagnostic techniques for electron density measurement in a 13.56MHz ICP reactor in pure Ar: the cutoff probe, hairpin probe, and a microwave interferometer. The interferometer showed the highest density, followed by the hairpin and cutoff probes, indicating that the probe antenna surface acts as a loss channel for charged particles, leading to a reduction in electron density. Furthermore, we found that the perturbation is localized near the probe.
• Towards calibration of picosecond O-TALIF
  
  • Shu Z
  • Latorre Sopie
  • Billeau J.B.
  • Booth Jean-Paul
  • Seletskiy D.V.
  • Reuter Stefan
  • Popov N.A.
  • Starikovskaia Svetlana
  , 2025. Experimental procedure of obtaining the Xe/O two-photon absorption cross-section ratio is discussed for nanosecond and picosecond TALIF experiments. The same nanosecond capillary discharge with 100% oxygen dissociation at 30 mbar pressure is used as a source of O-atoms.
• Modeling of N2-H2 DC discharges for ammonia production
  
  • Alves Luis Lemos
  • Pereira P
  • Baghel S.S.
  • Goncalves A.
  • Budde Maik
  • Booth Jean-Paul
  • Guaitella Olivier
  • Pinhão N.
  • Pintassilgo C D
  • Marques L.
  , 2025. In this work we present the on-going validation of a kinetic model for nitrogen-hydrogen plasmas, highlighting the significance of plasma-surface interactions in ammonia production.
• BepiColombo cruise science: overview of the mission contribution to heliophysics
  
  • Sánchez-Cano Beatriz
  • Hadid Lina Z
  • Aizawa Sae
  • Murakami Go
  • Bamba Yumi
  • Chiba Shota
  • Hara Takuya
  • Heyner Daniel
  • Ho George
  • Iwai Kazumasa
  • Kilpua Emilia
  • Kinoshita Gaku
  • Lavraud Benoit
  • Miyoshi Yoshizumi
  • Pinto Marco
  • Schmid Daniel
  • Shiota Daikou
  • Vainio Rami
  • Andre Nicolas
  • Aronica Alessandro
  • Asmar Sami
  • Auster Hans-Ulrich
  • Barabash Stas
  • Barthe Alain
  • Baumjohann Wolfgang
  • Benkhoff Johannes
  • Bentley Mark
  • Bunce Emma
  • Cappuccio Paolo
  • Delcourt Dominique
  • Di Stefano Ivan
  • Doria Irene
  • Dresing Nina
  • Fedorov Andrei
  • Fischer David
  • Fiethe Bjorn
  • Fränz Markus
  • Gieseler Jan
  • Giner Franz
  • Giono Gabriel
  • Harada Yuki
  • Hussmann Hauke
  • Iess Luciano
  • Imamura Takeshi
  • Jeszenszky Harald
  • Jones Geraint
  • Katra Bruno
  • Kazakov Adrian
  • Kozyrev Alexander
  • Laky Gunter
  • Lefevre Carlo
  • Lichtenegger Herbert
  • Lindsay Simon
  • Lucente Marco
  • Magnafico Carmelo
  • Magnes Werner
  • Martindale Adrian
  • Matsuoka Ayako
  • Milillo Anna
  • Mitrofanov Igor
  • Nishiyama Gaku
  • Oleynik Philipp
  • Orsini Stefano
  • Paik Meegyeong
  • Palmroos Christian
  • Plainaki Christina
  • Penou Emanuel
  • Persson Moa
  • Quarati Francesco
  • Quémerais Eric
  • Richter Ingo
  • Robidel Rozenn
  • Rojo Mathias
  • Saito Yoshifumi
  • Santoli Francesco
  • Stark Alexander
  • Stumpo Mirko
  • Tian Rong
  • Varsani Ali
  • Verdeil Christopher
  • Williamson Hayley
  • Witasse Olivier
  • Yokota Shoichiro
  Earth Planets and Space, Springer / Terra Scientific Publishing Company, 2025, 77, pp.114. BepiColombo, the joint ESA/JAXA mission to Mercury, was launched in October 2018 and is scheduled to arrive at Mercury in November 2026 after an 8-year cruise. Like other planetary missions, its scientific objectives focus mostly on the nominal, orbiting phase of the mission. However, due to the long duration of the cruise phase covering distances between 1.2 and 0.3 AU, the BepiColombo mission has been able to outstandingly contribute to characterise the solar wind and transient events encountered by the spacecraft, as well as planetary environments during the flybys of Earth, Venus, and Mercury, and contribute to the characterisation of the space radiation environment in the inner Solar System and its evolution with solar activity. In this paper, we provide an overview of the cruise observations of BepiColombo, highlighting the most relevant science cases, with the aim of demonstrating the importance of planetary missions to perform cruise observations, to contribute to a broader understanding of Space Weather in the Solar System, and in turn, increase the scientific return of the mission. (10.1186/s40623-025-02256-z)
  DOI : 10.1186/s40623-025-02256-z