Publications

2025

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
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
Hybrid simulations of Mercury’s global dynamics and the interplanetary ions’ precipitation fluxes under different interplanetary conditions
- Cazzola E.
- Fontaine D.
- Modolo Ronan
Astronomy & Astrophysics - A&A, EDP Sciences, 2025, 701, pp.A209. Aims . We aim to quantify the impact of different interplanetary conditions met by Mercury along its orbit between its aphelion (~0.47 AU) and perihelion (~0.31 AU) on the Hermean environment, including the rate of solar-wind ion precipitation onto the surface. Methods . We performed a set of 3D global hybrid simulations (kinetic ions and fluid electrons) with interplanetary conditions taken from recent statistics from observations on board the Parker Solar Probe and MESSENGER missions in such a way as to represent an average scenario at both the aphelion and perihelion positions, and in the cases of a slow (250 km/s) and fast (450 km/s) solar wind. Results . The results are in general agreement with empirical models. However, we have found that the subsolar stand-off distances of magnetopause and bow shock, respectively, in the range of 1.0–1.4 R M and 1.3–2.0 R M , are relatively shorter than global statistical averages of, respectively, 1.45 and 1.96 R M . We also observe a local time (LT) asymmetry in the cusp’s location, with the northern cusp located in the post-noon sector centred around 13–14.3 LT and the southern cusp located in the pre-noon sector centred around 9–10.7 LT. Noticeably, the southern cusp region takes the shape of a parallelogram extended from southern middle latitudes in the pre-noon sector to equatorial latitudes in the post-noon sector. We suggest that these effects could result from the orientation of the interplanetary magnetic field along the Parker spiral, which is characterised by an almost radial orientation with a small duskward component. (10.1051/0004-6361/202553953)
DOI : 10.1051/0004-6361/202553953
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>
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<sub>⊥</sub>∣<sup>2</sup>/∣E∣<sup>2</sup> of beam-generated turbulent Langmuir/Z-mode ($\mathcal{LZ}$) waves and electromagnetic emissions radiated at plasma frequency ω<sub>p</sub> 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<sub>p</sub> 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
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
Plasma Pressure Response to Non-Inductive Current Drive in Axisymmetric Viscoresistive MHD Steady-states
- Krupka Anna
- Firpo Marie-Christine
Journal of Plasma Physics, Cambridge University Press (CUP), 2025, 91 (4), pp.E126. <div><p>We investigate self-consistent, steady-state axisymmetric solutions of incompressible tokamak plasma using a visco-resistive magnetohydrodynamic model. A key contribution of this work is the formulation of Poisson's equation that governs the pressure profile. Our analysis reveals that the current modeling fails to produce realistic pressure levels. To overcome this limitation, we introduce additional non-inductive current drives, akin to those generated by neutral beam injection or radio frequency heating, modeled as modifications to the toroidal current. Numerical simulations validate our enhanced model, showing significant improvements in pressure profile characteristics. In the cases examined, the effect of these current drives on the velocity profiles is moderate, except when the non-inductive current drives induce reversals in the total toroidal current density, leading to non-nested flux surfaces with internal separatrices.</p></div> (10.1017/S0022377825100743)
DOI : 10.1017/S0022377825100743
Pre-flight performance of the ion energy mass spectrum analyzer for the Martian Moons eXploration (MMX) mission
- Yokota Shoichiro
- Matsuoka Ayako
- Murata Naofumi
- Saito Yoshifumi
- Asamura Kazushi
- Kasahara Satoshi
- Delcourt Dominique
- Hadid Lina Z
- Terada Naoki
- Keika Kunihiro
- Harada Yuki
- Nakagawa Hiromu
- Masunaga Kei
- Sakai Shotaro
- Futaana Yoshifumi
- Imajo Shun
- Seki Kanako
- Nishino Masaki N
- Kitamura Yuki
Progress in Earth and Planetary Science, Springer/Japan Geoscience Union, 2025, 12 (1), pp.51. Abstract An ion energy mass spectrum analyzer was developed for the Martian Moons eXploration (MMX) mission to measure the three-dimensional velocity distribution function and mass profile of low-energy ions around the Mars-Moon system. The hemispheric field-of-view (FOV) is acquired by a pair of angular scanning deflectors, and the energy/charge and mass/charge are determined for each ion by an electrostatic analyzer and a linear-electric-field (LEF) time-of-flight (TOF) analyzer, respectively, with an enhanced mass resolution of $$m/\Delta m\sim 100$$ m / Δ m ∼ 100 . The ion analyzer, together with magnetometers, constitutes the mass spectrum analyzer (MSA), one of the scientific instruments on board the MMX spacecraft. This paper describes the instrumentation of the ion analyzer, and results of the performance tests of its flight model (FM). (10.1186/s40645-025-00718-2)
DOI : 10.1186/s40645-025-00718-2
Statistical properties of beam-driven upper-hybrid wave turbulence in the solar wind
- Annenkov V.
- Krafft C.
- Volokitin A.
- Savoini P.
Astronomy & Astrophysics - A&A, EDP Sciences, 2025, 699, pp.L6. We studied the statistical properties of beam-driven upper-hybrid wave turbulence in the solar wind by focusing on the probability density functions (PDFs) of electric field amplitudes, |E|. We used, for the first time, high-resolution and long-term 2D particle-in-cell simulations of the interaction of an electron beam with a magnetized plasma to calculate and analyse the skewness (degree of anisotropy) and the kurtosis (degree of flatness) of the PDFs of |E| and log|E|2 for various intensities of plasma magnetization (Ω = ωc/ωp) and average levels of random density fluctuations (ΔN). Using the Pearson classification, we show that the PDFs of log|E|2 predominantly align with Type VI Pearson distributions, with a shift towards Type I at high plasma magnetizations. In contrast, the PDFs of |E| are Type I Pearson distributions regardless of the Ω and ΔN values. Comparisons between simulation results and observations by the Solar Orbiter’s Time Domain Sampler instrument show a good agreement. This study also offers a promising method for understanding the dynamics of wave turbulence and indirectly estimating plasma magnetization. (10.1051/0004-6361/202555087)
DOI : 10.1051/0004-6361/202555087
Asymmetric dual cascade in gravitational wave turbulence
- Gay Benoît
- Galtier Sébastien
Physica D: Nonlinear Phenomena, Elsevier, 2025, 477, pp.134712. (10.1016/j.physd.2025.134712)
DOI : 10.1016/j.physd.2025.134712
Ideal and resistive impurity parallel-velocity-gradient instability
- Cuerva-Lazaro G
- Lesur Maxime
- Gürcan O
- Bourgeois J
- Maestracci C
- Gravier E
- Kosuga Y
Plasma Physics and Controlled Fusion, IOP Publishing, 2025, 67 (7), pp.075019. The presence of impurity ions in magnetically confined plasmas can significantly influence micro-instabilities, impacting cross-field transport and ultimately affecting fusion performance. In particular, Parallel Velocity Gradient (PVG) instability, commonly observed at the edge of fusion devices and in linear devices, can be strongly influenced by impurities. Inspired by the drift-wave models of Hasegawa-Mima and Hasegawa-Watakani, this article develops and examines two distinct fluid models: the ideal impurity-PVG model and the resistive impurity-PVG model. These models aim to investigate the impact of impurities on key properties of the PVG instability, both in the linear and nonlinear regimes. Our findings show that non-negligible impurity concentrations change the growth rates, wave-number ranges, and nonlinear saturations of these instabilities. Notably, the degree of ionization and the relative impurity flow shear can either amplify or mitigate PVG-related turbulence, depending on the impurity and overall plasma conditions. The results underscore the need for a more comprehensive treatment of multi-ion-species plasmas, particularly when impurity fractions cannot be treated as traces. (10.1088/1361-6587/ade4fb)
DOI : 10.1088/1361-6587/ade4fb
Automated Nanosecond Plasma Jets for Targeted Medical Treatments
- Billeau Jean-Baptiste
- Radu Vlad-Stefanut
- Polprasarn Kasidapa
- Gérôme Frédéric
- Benabid Fetah
- Pai David
- Seletskiy Denis
- Reuter Stephan
- Starikovskaia Svetlana
, 2025, pp.MC14 : Sources de particules chargées, Plasmas.
Spectroscopic investigations of a filament reconnecting with coronal loops during a two-ribbon solar flare
- Joshi Reetika
- Dudík Jaroslav
- Schmieder Brigitte
- Aulanier Guillaume
- Chandra Ramesh
Astronomy & Astrophysics - A&A, EDP Sciences, 2025, 698, pp.A301. Context. In the standard 2D model of eruption, the eruption of a magnetic flux rope is associated with magnetic reconnection occurring beneath it. However, in 3D, additional reconnection geometries are possible, in particular the AR – RF , where external reconnection involving the overlying arcades ( A ) and erupting flux rope ( R ) turns into another arcade and a flare loop ( F ). This process results in the drifting of the legs of the erupting flux rope. Aims. We investigate spectroscopic signatures of such AR – RF reconnection occurring in an erupting filament reconnecting with coronal arcades during a weak B3.2-class two-ribbon flare. Methods. We examined the evolution of the erupting filament eruption using imaging observations by the Atmospheric Imaging Assembly (AIA) as well as both imaging and spectroscopic observations by the Interface Region Imaging Spectrograph (IRIS). Results. As the filament rises into the corona, it reconnects with the surrounding arcade of coronal loops with localized brightenings, resulting in the disappearance of the coronal loops and formation of a hot flux rope, showing a slipping motion of its footpoints that extends to the previous footpoints of the coronal loops ( AR – RF reconnection), as was predicted by the 3D extensions to the standard solar flare model. These brightenings are accompanied by the presence of strong blueshifts in both the IRIS Si IV and Mg II lines, up to ≈200 km s −1 . The lines are also extremely wide, with nonthermal widths above 100 km s −1 . Furthermore, a strongly non-Gaussian profile of the most blueshifted component is detected at the start of the AR – RF reconnection, indicating the presence of accelerated particles and magnetohydrodynamic turbulence, and associated with the appearance of hot plasma in the AIA 94 Å passband. Results. For the first time, an observation has been reported in which the IRIS slit successfully captures AR – RF reconnection between a filament and overlying arcades, resulting in strong blueshifts and very broad line profiles. (10.1051/0004-6361/202554011)
DOI : 10.1051/0004-6361/202554011
Cross-Analysis of Magnetic and Current Density Field Topologies in a Quiescent High Confinement Mode Tokamak Discharge
- Firpo Marie-Christine
Foundations, MDPI, 2025.
Initiation Route of Coronal Mass Ejections. II. The Role of Filament Mass
- Xing Chen
- Cheng Xin
- Aulanier Guillaume
- Ding Mingde
The Astrophysical Journal, American Astronomical Society, 2025, 986 (1), pp.37. Abstract A thorough understanding of the initiation of coronal mass ejections (CMEs), which is manifested as a slow rise of pre-eruptive structures before the impulsive ejection in kinematics, is key for forecasting solar eruptions. In our previous work, we showed that the slow rise of a hot flux rope with coronal mass density is caused by the moderate magnetic reconnection occurring in the hyperbolic flux tube (HFT) combined with the torus instability. However, it remains unclear how the initiation process varies when a filament is present in the pre-eruptive flux rope. In this work, we reveal the complete initiation route of a CME containing filament mass with a state-of-the-art full-magnetohydrodynamics simulation. The comprehensive analyses show that the filament mass has an important impact on the CME initiation through triggering and driving the slow rise of flux rope with its drainage, besides the contributions of HFT reconnection and torus instability. Finally, in combination with our previous work, we propose that the enhanced drainage of filament mass and various features related to the HFT reconnection, such as the split of pre-eruptive structure and the preflare loops and X-ray emissions, can serve as precursors of CME initiation in observations. (10.3847/1538-4357/adceb5)
DOI : 10.3847/1538-4357/adceb5
Evolution of Solar Wind Turbulence during Radial Alignment of Parker Solar Probe and Solar Orbiter in 2022 December
- Silwal Ashok
- Zhao Lingling
- Zhu Xingyu
- Sorriso-Valvo Luca
- Hadid Lina
- Zank Gary
- Li Hui
- Badman Samuel
- Rivera Yeimy
- Gautam Sujan Prasad
- Karki Monika
- Alonso Guzman Juan
- M. Subashchandar Nibuna
- Jin Zeping
The Astrophysical Journal Supplement Series, IOPscience, 2025, 278 (2), pp.40. Abstract We investigate the radial evolution of solar wind turbulence during the radial alignment of Parker Solar Probe (PSP) and Solar Orbiter (SO) on 2022 December 10, with PSP located at approximately 0.11 au and SO near 0.88 au. To identify nearly the same plasma parcel crossing both spacecraft, we apply a ballistic propagation model with time-constant acceleration constrained by in situ solar wind velocity measurements at PSP and SO. We trace the magnetic footpoint of the plasma parcel back to the photosphere using a potential field source surface model based on a Global Oscillations Network Group synoptic magnetogram. Field and plasma measurements from PSP and SO are used to analyze power spectral density (PSD), spectral scaling, magnetic compressibility, and intermittency. Our results show that (1) the trace PSD of magnetic fluctuations steepens in the inertial range and flattens in the dissipation range with increasing radial distance; (2) the spectral break shifts to lower frequencies at SO; and (3) the Castaing model reveals multifractal intermittency in the inertial range, with slightly weaker intermittency at SO. These findings based on the same plasma parcel are consistent with the results of statistical studies on the radial evolution of turbulence and provide a reference for theoretical modeling of turbulence in the inner heliosphere. (10.3847/1538-4365/add011)
DOI : 10.3847/1538-4365/add011

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