Scientific publications

2026

• Plasma plume symmetrization by electron rotation and ion detachment properties in a diverging magnetic nozzle
  
  • Pioch Romain
  • Chabert Pascal
  • Désangles Victor
  Physical Review E, American Physical Society (APS), 2026, 113 (3), pp.035209. The ion flux direction in a rapidly diverging magnetic field and the role of Earth's magnetic field in plasma dynamics are investigated experimentally using a low power electron cyclotron resonance thruster. The comparison between ion trajectories measured with a directional Faraday cup and the magnetic field geometry allows us to assess some of the ion flow properties. The results show that the ion trajectories follow the magnetic field lines in the center part of the plasma plume but not on its edges, defining the detachment location. Once detached, ions follow straight line trajectories, and their detachment has a divergent nature. The effect of the thruster operating condition on these properties is explored. Plasma potential measurements carried out with an emissive probe reveal the presence of a large radial electric field, pointing outward at the detachment point, that explains the divergent nature of the ion detachment. The amplitude of the induced E × B drift rotation of the electrons in the nozzle damps the disymmetrizing influence of Earth's magnetic field on the electron dynamics and leads to an axisymmetric plasma plume. This mechanism is demonstrated using single particle simulations. (10.1103/3twz-bcvk)
  DOI : 10.1103/3twz-bcvk
• Climatology of Plasma Irregularities Using ROTI Index From 2008 to 2023 in East West Asia
  
  • Drabindra Pandit
  • Rolland Fleury
  • Christine Amory‐mazaudier
  Space Weather: The International Journal of Research and Applications, American Geophysical Union (AGU), 2026, 24 (4), pp.e2025SW004759. This study investigates characteristics of ionospheric irregularities over the East–West Asian equatorial region using the Rate of TEC Index (ROTI) derived from Global Navigation Satellite System (GNSS) measurements. Data from four stations (GUAM, PIMO, CUSV, and IISC) were analyzed for 2008–2023, covering solar cycle (SC) 24 and the ascending phase of SC 25. While our findings are generally aligned with previous research, this work presents new insights into the complex behavior of ionospheric scintillation in this sector. A key finding is the significant spatial variability in irregularity occurrence, with stations at similar magnetic dip (11–13°) exhibiting varying activity levels. Notable longitudinal asymmetries were also identified, particularly at GUAM, which shows reduced autumnal activity, likely due to local differences in Pre‐Reversal Enhancement (PRE) and magnetic declination. Our study shows a clear daily pattern: scintillation begins after sunset (18:00–19:00 LT), peaks in the late evening (20:00–21:30 LT), and declines by early morning. A slight increase in ROTI is consistently observed just before sunrise at all locations. Temporally, results show dependence on the 11‐year SC and a distinct seasonal pattern, with activity concentrated in equinoctial months. The spring maximum is generally stronger than the autumn one across stations. Finally, although the long‐term trend follows the SC, the relationship is non‐linear. Outliers, such as anomalous activity in 2019, demonstrate that while the Sunspot Number (SSN) is a primary long‐term driver, scintillation is also modulated by short‐term geophysical phenomena. (10.1029/2025SW004759)
  DOI : 10.1029/2025SW004759
• Mutual impedance experiments in a laboratory plasma: Experimental validation of numerical modeling
  
  • Dazzi P.
  • Henri P.
  • Bucciantini L.
  • Briaud E.
  • Brochot J. Y.
  • de Keyser J.
  • Edberg N. J. T.
  • Issautier K.
  • Kretzschmar Matthieu
  • Lecas T.
  • Revillet C.
  • Souffi H.
  • Vengeons G.
  • Wattieaux G.
  Astronomy & Astrophysics - A&A, EDP Sciences, 2026, 707. Context. In situ measurements of space plasma are necessary to explore heliospheric and planetary ionized environments. Mutual impedance experiments are an active plasma diagnostic technique used to measure the properties of space plasmas, including the plasma density and the electron temperature. Although various models have been developed for unmagnetized space plasmas, they fail to describe the instrument behavior in magnetized plasmas, such as the ionosphere and magnetosphere of magnetized planets and moons. A quantitative instrument model of the mutual impedance experiment is required, however, for current and future space missions, including ESA/JAXA BepiColombo and ESA JUICE, which will both conduct mutual impedance experiments (PWI/AM2P and RPWI/MIME, respectively). Aims. We develop an instrument model for exploring and quantitatively characterizing mutual impedance experiment measurements performed in planetary plasmas, with the goal of providing in situ diagnostics of the plasma density and electron temperature. Methods. To reach this goal, we combined numerical investigation and laboratory experiments. We investigated the experimental regime of high magnetization for the first time, where the electron gyrofrequency is higher than the plasma frequency, both experimentally and numerically. On the experimental side, we built a setup composed of a plasma chamber, a mutual impedance experiment, and a Langmuir probe. With this, we achieved a controlled plasma environment representative of magnetized space plasmas, which we diagnosed with two independent plasma instruments. On the numerical side, we developed a model for magnetized mutual impedance experiments that took the geometry of the mutual impedance antennas and the plasma chamber into account and that employed a kinetic linear description of the plasma electrons. Results. First, we characterized the plasma environment generated in the plasma chamber: the achievable plasma parameters, the stability, and the repeatability of the plasma conditions. Second, we validated the instrument model by comparing the numerical model predictions to the measurements obtained in the plasma chamber. Third, we extracted the plasma density and temperature from in situ mutual impedance measurements using our new numerical instrument model, and we validated them using the independent in situ measurements from the Langmuir probe. Conclusions. This work (i) proves that mutual impedance experiments are able to provide robust plasma diagnostics in a magnetized space plasma environment, and (ii) develops a methodological framework that will be used for the planetary space missions BepiColombo and JUICE to perform both the in-flight calibration and the exploitation of the measurements from PWI/AM2P and RPWI/MIME, respectively, in the magnetospheres of Mercury, Jupiter, and Ganymede. (10.1051/0004-6361/202554409)
  DOI : 10.1051/0004-6361/202554409
• Global plasma modeling of an air-breathing gridded-ion thruster for very low Earth orbit applications
  
  • Carer Charlélie
  • Verdier Solène
  • Flack Léo
  • Scemama Adrien
  • Petronio Federico
  Physics of Plasmas, American Institute of Physics, 2026, 33 (8). A volume-averaged (zero-dimensional) global model of an atmospheric nitrogen–oxygen mixture is proposed. This model is used to predict the performance of an air-breathing electric gridded-ion thruster. Based on particle and energy balance equations, it computes the densities and temperatures of the different species in the discharge chamber and evaluates the thrust generated by ions extracted from the plasma and accelerated between two grids. Simulation results over a range of input radio frequency (RF) powers and altitudes are used to assess the feasible operating regimes and to identify the main limiting mechanisms. Coupling the global model with a simplified drag analysis indicates that satellite operation should be feasible at altitudes between 200 and 250 km, for RF power levels ranging from 1.5 to 3 kW. However, certain limitations associated with the gas compression system and drag estimation deserve further investigation. (10.1063/5.0327675)
  DOI : 10.1063/5.0327675
• Plasma Dynamics and Structure of Titan's Induced Magnetosphere From Wave, Magnetic Field, and Plasma Measurements
  
  • Kim K.
  • Modolo Ronan
  • Edberg N J T
  • Morooka M.
  • Romanelli N.
  • Moissard C.
  • Holmberg M K G
  • Bertucci C.
  • Berthelier Jean-Jacques
  • Canu P.
  • Piberne R.
  • Coates A J
  • Dubinin E.
  • Regoli L.
  • Kurth W S
  • Wahlund J.‐e.
  • Waite J H
  • Dougherty M K
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2026, 131 (4). In this study, we combine Cassini fields and particle observations to investigate Titan's induced magnetosphere from the TA to T82 flybys, including flybys from the Cassini prime, equinox, and part of the solstice mission, to investigate the average location and the shape of Titan's induced magnetosphere. Although earlier studies have provided valuable information on Titan's induced magnetosphere, they were largely based on separate analyses of fields and particle data. We provide an integrated map of electron density and temperature in Titan's near plasma environment to outline the external boundary of the induced magnetosphere. We identify a dense ionospheric region and an extended plasma wake with electron densities ranging between 10^-2 and 10³ cm^-3. In addition, we systematize the spatial distribution of pick-up ions at Titan with respect to the background convective electric field. We indicate that pickup ions are found in the positive hemisphere of the Kronian plasma convective electric field. The mass of the observed pickup corresponds to methane group ions, N$_2^+$ ions as well as protons and molecular hydrogen ions. The Kronian background electric field progressively accelerates these ions, and we estimate its intensity by reconstructing the radial energy gain of this population in response to the convective electric field. We find the estimated from the pickup ions electric field values within 0.05 mV m^-1 and 1.92 mV m^-1 range, which is consistent with an estimate of 0.61 mV m^-1 deduced from |v_corot x B| computation. (10.1029/2025JA034830)
  DOI : 10.1029/2025JA034830
• Hall thruster modeling with multiple simulation techniques: Model benchmarking, fluid–kinetic consistency, and experimental validation
  
  • Petronio Federico
  • Alvarez Laguna Alejandro
  • Bourdon Anne
  • Lafleur Trevor
  • Chabert Pascal
  Journal of Applied Physics, American Institute of Physics, 2026, 139 (9), pp.093303. Numerical plasma models are critical tools for aiding the design and understanding of electric propulsion systems, such as Hall thrusters, particularly when considering challenges associated with diagnostic access and reliable internal measurements. For complex plasma systems, such as Hall thrusters, theoretical verification solutions are often missing, and therefore, benchmarking represents an important element in assessing the correctness and consistency of the underlying mathematical model, and the computational performance of the numerical implementation. In this work, we benchmark three different numerical codes by simulating an SPT-100 Hall thruster under identical operating conditions. The codes include one-dimensional stationary and non-stationary fluid models describing the axial thruster direction, as well as a two-dimensional axial–azimuthal Particle-In-Cell/Monte Carlo Collision (PIC/MCC) model. A partial validation is performed with available experimental measurements of the discharge current, thrust, and anode specific impulse, showing good agreement. Overall, the fluid and PIC/MCC models compare favorably with each other, and several fluid approximations are found to be acceptable. For example, axial electron energy transport is relatively minor such that the electron temperature is reasonably determined by a local energy balance. Other approximations, however, require a more careful examination: particularly the assumption of Maxwellian electrons and the neglect of electron–wall collisions in the electron momentum balance equations. (10.1063/5.0305019)
  DOI : 10.1063/5.0305019
• Relativistic Feedback Discharges in Dielectric Solids
  
  • Pasko Victor P
  • Celestin Sebastien
  • Bourdon Anne
  Physical Review Letters, American Physical Society, 2026, 136 (9), pp.095301. The photoelectric feedback processes leading to growth of relativistic runaway electron avalanches are believed to be responsible for extreme uxes of gamma rays produced from very compact regions of space with dimensions on the order of hundred meters in association with lightning activity in the Earths natural environment (Pasko et al., 2025, https://doi.org/10.1029/2025JD043897). Here we demonstrate for the rst time that the same photoelectric feedback discharges can be realized on centimeter scales in common solid state dielectric materials, like quartz, acrylic and bismuth germanate. These discharge can serve as new sources of high energy X-ray radiation. (10.1103/4p6l-rzck)
  DOI : 10.1103/4p6l-rzck
• 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, 2026. 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
• Future trajectories of the BepiColombo MPO and Mio spacecraft: a quantitative tool for magnetospheric region prediction
  
  • Hollman Daragh M
  • Jackman Caitríona M
  • Domijan Katarina
  • Bowers Charles F
  • Hadid Lina Z
  • Heyner Daniel
  Earth Planets and Space, Springer / Terra Scientific Publishing Company, 2026, 78 (1), pp.188. Mercury possesses one of the most dynamic magnetospheres in our solar system, with strong driving by the solar wind, and significant motion of the magnetospheric boundaries in response. The BepiColombo mission will provide the first dual-spacecraft view of this system. In order to maximise the scientific output from BepiColombo, we need quantitative predictions of which magnetospheric region each spacecraft will be sampling at any given time. This is important for the planning of spacecraft operations, where the coordination and collaboration of many instruments across two spacecraft is vitally important, not only for science, but also due to telemetry and power limitations. In this work, we outline a new method using MESSENGER observations to make quantified predictions, with uncertainties, of the probability of observing solar wind, magnetosheath, and magnetosphere for a given position in Mercury’s magnetospheric environment. We apply this technique to five of the six completed BepiColombo Mercury flybys, and additionally forecast magnetospheric region sampling during a representative 10-hour interval of the nominal science mission. We aim to make this approach as accessible as possible, and include in a software repository simple worked examples to aid users in applying these predictions in their own research. (10.1186/s40623-026-02515-7)
  DOI : 10.1186/s40623-026-02515-7
• First in Situ Detection of the Magnetic Component of a Solar Type III Radio Wave
  
  • Kretzschmar Matthieu
  • Vecchio Antonio
  • Krasnoselskikh Vladimir
  • Maksimovic Milan
  • Soucek Jan
  • Pisa David
  • Gasque Claire
  • Bale Stuart D.
  • Dudok de Wit Thierry
  • Pulupa Marc
  • Khotyaintsev Yuri V.
  • Chust Thomas
  • Jannet Guillaume
  • Brochot Jean-Yves
  • Revillet Claire
  • Fergeau Patrice
  • Bonnin Xavier
  • Goetz Keith
  The Astrophysical Journal Letters, Bristol : IOP Publishing, 2026, 1001. Solar radio bursts, and astrophysical radio emissions in general, are observed either in space or on the ground by measuring their fluctuating electric field. Here, we report the first measurement of the magnetic component of a solar radio wave, observed simultaneously by the Solar Orbiter and Parker Solar Probe missions. The observations were made during the type III radio burst on 2021 October 28. The analysis of the wave polarization and magnetic and electric field amplitudes allows us to estimate the refractive index and put constraints on the direction of the wave. The wave is found to be consistent with an ordinary-mode wave and with a source near the southeast limb of the Sun. These results pave the way for future observations and analyses of the magnetic field of radio waves, in particular, for solar radio bursts. (10.3847/2041-8213/ae5893)
  DOI : 10.3847/2041-8213/ae5893
• Self-consistent stabilization of large-scale linear magnetic holes via ion trapping
  
  • Ballerini Giulio
  • Arrò Giuseppe
  • Califano Francesco
  • Henri P.
  • Pucci Francesco
  • Simon Wedlund Cyril
  • Preisser Luis
  Physics of Plasmas, American Institute of Physics, 2026, 33. Magnetic holes (MHs) are localized depressions in the magnetic field commonly observed in space plasmas such as the solar wind, planetary magnetosheaths, and cometary environments. Despite the abundance of spacecraft observations, the mechanisms governing the generation of these structures are not fully understood. In this study, we investigate the stability of magnetic depressions in a controlled plasma environment via two-dimensional hybrid particle-in-cell simulations using the Menura code. Initializing the system with preexisting magnetic field depressions embedded in a mirror-stable plasma allows us to isolate the fundamental physical mechanisms responsible for stabilization and equilibrium. We analyze the roles of the initial depth, characteristic width, and magnetic field geometry of the depression. Our results demonstrate that narrow depressions (of the order of ion kinetic scales) are unstable, whereas broader structures can reach stable equilibria through ion trapping, resulting in localized density enhancements and temperature anisotropy consistent with in situ observations of large-scale MHs. The findings highlight the importance of ion trapping for stabilization and provide a controlled framework to investigate MH dynamics. (10.1063/5.0327618)
  DOI : 10.1063/5.0327618
• Disturbed and quiet days ∑O/N₂ variations at low and mid-latitudes during solar cycles 23 and 24
  
  • Khan Jahan Zeb
  • Younas Waqar
  • Amory-Mazaudier Christine
  • Khan Majid
  Advances in Space Research, Elsevier, 2026, 77 (5), pp.6295-6314. We analyzed the column density ratio of thermospheric compositions (∑O/N₂) using data from the Global Ultraviolet Imager (GUVI) onboard the TIMED satellite from 2002 to 2020. Daily ∑O/N 2 values for the three most geomagnetically disturbed and quietest days each month were used to compute monthly means at low and mid-latitudes across both hemispheres. These variations were also examined across various longitudinal sectors, including Asia, Africa, and the Americas. The fluctuations in ∑O/N₂ were more pronounced at mid-latitudes than at low latitudes, with low latitude values in both hemispheres peaking near the equinoxes. At midlatitudes, the highest values occurred during local winter, with stronger peaks in the Northern Hemisphere (NH) than in the Southern Hemisphere (SH). The winter and equinoctial maxima are also observed in all longitudinal sectors. Besides this, the distinct longitudinal asymmetries over Asian, African, and American regions at mid-latitudes, influenced by geomagnetic field geometry, are also observed. The downwelling of ∑O/N₂ in local winter is stronger, while upwelling in local summer is weaker in the longitudinal sectors containing the magnetic pole. Annual (AV) and semiannual variations (SAV) were extracted using a bandpass filter. AV was stronger at mid-latitudes, peaking in local winter and highlighting the winter anomaly in both hemispheres. SAV were dominant at low latitudes, with positive peaks at equinoxes and negative dips at solstices, generally in phase across hemispheres and longitude sectors. The amplitudes of AV and SAV are stronger during solar maximum periods, justifying the solar cycle trend. Analysis also revealed that during geomagnetically disturbed periods, ∑O/N₂ typically decreased (≤ -10%) at mid-latitudes and increased (≥10%) at low latitudes compared to quiet periods. Although opposite trends-enhancement at mid-latitudes and depletion at low latitudes -were occasionally observed, they were less significant. This study aims to provide valuable insights into the dynamics of thermospheric composition, thereby contributing to the improved modeling of ionospheric behavior and space weather forecasting. (10.1016/j.asr.2025.12.115)
  DOI : 10.1016/j.asr.2025.12.115
• Nonlinear phase synchronization and the role of spacing in shell models
  
  • Manfredini L.
  • Gürcan Ö D
  Physical Review E, American Physical Society (APS), 2026, 113 (1), pp.015101. A shell model can be considered as a self-similar chain of interacting triads, where each triad can be interpreted as a nonlinear oscillator that can be mapped to a spinning top. Investigating the relation between phase dynamics and intermittency in such a chain of nonlinear oscillators, it is found that synchronization is linked to increased energy transfer. In particular, our results indicate that the observed systematic increase of intermittency, as the shell spacing is decreased, is associated with strong phase alignment among consecutive triadic phases, facilitating the energy cascade. It is shown that while the overall level of synchronization can be quantied using a Kuramoto order parameter for the global phase coherence in the inertial range, a local, weighted Kuramoto parameter can be used for the detection of burst-like events propagating across shells in the inertial range. This novel analysis reveals how locally phase-locked states are associated with the passage of extreme events of energy ux. Applying this method to helical shell models ( i.e. for a class of helical interactions that couple the two helicities in a non separable topology) reveals that a reduction in phase coherence correlates with suppression of intermittency. When inverse cascade scenarios are considered using two dierent shell models including a non local helical shell model, and a local standard shell model with a modied conservation law, it was shown that a particular phase organization is needed in order to sustain the inverse energy cascade. It was also observed that the PDFs of the triadic phases were peaked in accordance with the basic considerations of the form of the ux, which suggests that a triadic phase of π/2 and -π/2 maximizes the forward and the inverse energy cascades respectively. (10.1103/2vxp-1k2t)
  DOI : 10.1103/2vxp-1k2t