Page test Net.Com

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
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
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
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 ωp 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 ωp 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
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
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>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.</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
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