As an integral part of planetary atmospheres, ionospheres are tightly coupled with the neutral atmosphere, exosphere and surrounding plasma environment, possessing rich compositional, density, and temperature structures. The interaction among neutral and charged components affects atmospheric loss, neutral winds, photochemistry, and energy balance within ionospheres.
This session invites abstracts concerning remote and in-situ data analysis, modelling studies, comparative studies, instrumentation and mission concepts for unmagnetized and weakly magnetized solar system bodies.
In the Dynamo Region of the Martian ionosphere a large-scale current is generated by collision of ions with the neutral wind while photoelectrons preferentially gyrate around local magnetic field lines. The direction and intensity of this current is locally determined by both the neutral wind velocity and ambient magnetic field. Using MAVEN magnetometer data, and a physics-informed neural network constrained by Ampere’s law of induction and Gauss's law for magnetism (the Neural-Curlometer technique), we compute a continuous high-resolution model of this current. We find that the ionospheric dynamo is located at altitudes of 125-200 km, is controlled by the interior magnetic field, and exhibits a clear seasonal variability. The currents coincide with the wind patterns theoretically estimated by global atmospheric circulation models and thus have the potential to significantly improve them.
How to cite: Delcourt, T. and Mittelholz, A.: Global Circulation of Martian Ionospheric Currents Revealed by Magnetometer Data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3809, https://doi.org/10.5194/egusphere-egu26-3809, 2026.
The plasma environment of a comet is a very structured and dynamic environment, involving complex interactions between the gas from the comet, the solar wind and the interplanetary magnetic field. Reasonably realistic models aiming to catch the global structure of this environment therefore become equally complex, requiring large numerical simulations which provide detailed output for which extensive analysis is needed to disentangle the various processes. We present something much simpler, in effect a self-consistent analytic hybrid model with kinetic treatment of ions and fluid description of electrons. The model is stationary in time, spherically symmetric and (presently) collisionless, includes only plasma originating from the gas emanating from the comet nucleus, and (in common with most models) neglects direct plasma interaction with the nucleus itself. Any applicability is thus restricted to the inner part of the coma outside of the immediate vicinity of the nucleus of a moderately active comet. Ion distribution functions and their moments as well as the electron temperature are analytically calculated at any point within this region. A particularly interesting feature of the model is the energetics, describing the transfer of energy from the electron gas to the ions and thus relating the ion flow speed and the ion and electron temperatures to the mean energy an electron obtains when released from its parent molecule.
How to cite: Eriksson, A. and Vigren, E.: An analytic hybrid model of cometary plasma, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10803, https://doi.org/10.5194/egusphere-egu26-10803, 2026.
The martian atmosphere is sensitive to disturbances in interplanetary space due to the absence of a strong planetary magnetic field. Solar energetic particle (SEP) events comprise high-energy, electrically-charged sub-atomic particles and are produced during solar flares and coronal mass ejections. Previous work has shown that SEPs result in diffuse aurorae, disruption of radio propagation, the dispersion of atmospheric compounds, and the ionisation of atmospheric layers. In this study, we explore the relationship between SEP events and lower-atmospheric heating at Mars. Five SEP events with durations of four days or longer were identified in the years 2020-2021. Measurements from the Mars Atmosphere And Volatile EvolutioN (MAVEN) mission and the Trace Gas Orbiter (TGO) spacecraft are compared to atmospheric temperature profiles derived from the Mars Climate Database. Specifically, Mars’ lower-atmospheric temperature profiles before, during and after the SEP events are analysed. No strong evidence is found that indicates SEP events lead to the heating of Mars’ atmosphere. However, in the one case, a SEP event occurred concurrently with an expanding global dust storm. In this case, a clear heating effect is observed, but further research is required to attribute atmospheric temperature variations as a result of the global dust storms and SEP events where the two occur simultaneously.
How to cite: Williams, L., Wild, J. A., Sanchez-Cano, B., Lopez Valverde, M.-A., and Gonzalez-Galindo, F.: Do Solar Energetic Particle events impact lower-atmospheric temperatures on Mars? , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4995, https://doi.org/10.5194/egusphere-egu26-4995, 2026.
During its fourth Venus flyby on 18 February 2025, Solar Orbiter reached an altitude of 378 km, significantly deeper than during previous encounters, allowing the spacecraft to enter the Venusian ionosphere for the first time. The Magnetometer (MAG) and Radio and Plasma Wave (RPW) instruments operated in burst mode during most of the flyby, providing high-time-resolution measurements of the entire induced magnetosphere. The peak electron density reached approximately 2x104 cm-3, derived from a spacecraft potential of about –45 V and calibrated using the plasma frequency line.
Solar Orbiter approached Venus from the tail region and entered the plasma environment without detecting a clear inbound bow shock. The upstream solar wind was steady and calm, as observed a few hours before and after the flyby and inferred from stable magnetosheath conditions, resulting in a structured and relatively steady plasma environment. High-cadence electron density measurements resolved fine-scale structures within plasma regions and boundaries, particularly at the ionopause, on spatial scales of 1–10 km, comparable to the local H+ and O+ ion length scales (2 and 8 km, respectively). Assuming an electron temperature of 0.5 eV, pressure balance was found across the ionopause, while quasi-periodic density and magnetic field variations suggest boundary oscillations on ion length scales during the pass. Near closest approach, magnetic flux ropes were observed. These features were generally not in full pressure balance with the surrounding plasma and exhibited small-scale perturbations in both magnetic field strength and density, consistent with a dynamically evolving rather than stationary state.
How to cite: Edberg, N. J. T., Boldu, J., Eriksson, A. I., Kim, K., Persson, M., Andews, D. J., Khotyaintsev, Y. V., Vecchio, A., Maksomovic, M., Chust, T., Hadid, L. Z., Horbury, T. S., Galand, M. I. F., Matteini, L., Pisa, D., Soucek, J., Kretzschmar, M., Owen, C. J., and Bale, S. D.: Measurements of Venus' plasma environment during the 4th Solar Orbiter flyby, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5088, https://doi.org/10.5194/egusphere-egu26-5088, 2026.
The solar wind interaction with Mars, lacking a global magnetic field, directly impacts its ionosphere, inducing currents to deflect the interplanetary magnetic field (IMF). These currents ultimately drive part of the atmospheric ion loss to space. This study estimates and characterizes these currents using MAVEN data over a long period, examining the influence of crustal magnetism and solar wind activity. Spherical polar magnetic field maps and Ampère's law are used to calculate current densities. Our analysis also considers both the absence of the south pole's crustal fields in order to obtain the “pure” ionospheric current system. Separately, we also study the effects of varying solar wind dynamic pressure. Results show current structures at the induced magnetosphere boundaries, closing in the ionosphere with hemispheric and dawn-dusk asymmetries, as in previous related studies. In areas where crustal magnetic fields are weaker, the IMF generally penetrates deeper. For the first time, we estimate variations in the induced current system due to solar wind pressure changes, showing that when the dynamic pressure rises the magnetosphere contracts and intensifies the currents closer to Mars. Finally, we comment on these results in the context of the potential future exploration of Mars.
How to cite: Andrews, D. and Kolokotronis, A.: Electrodynamic currents in near-Mars space , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10821, https://doi.org/10.5194/egusphere-egu26-10821, 2026.
Wave activity in the cometary plasma environment occurs across various levels of cometary activity, from large heliocentric distances to perihelion. These waves play a key role in the thermalisation of cometary pick-up ions and energy redistribution. Starting thousands of kilometres upstream of the nucleus, the gyrating motion of solar wind and cometary ions produces highly anisotropic velocity distributions, which can drive various wave phenomena.
In this study, we employ the 3D hybrid particle simulation code Amitis to model a cometary magnetosphere at approximately Mars’ distance in the solar wind, assuming an outgassing rate of Q ≈ 1027 s-1. The simulations reveal large-scale wave structures extending from far upstream of the comet nucleus to downstream of the bow shock. Wave signatures are most pronounced in the +E hemisphere and near the quasi-parallel bow shock, while the −E hemisphere is dominated by magnetic field pile-up. In the inner magnetosphere, where cometary ions dominate, waves are absent. Magnetic field peaks and solar wind density enhancements are out of phase—characteristics consistent with slow magnetosonic waves.
These waves amplify solar wind density, increasing dynamic pressure and potentially contributing to the formation of magnetosheath jets. Our simulations indicate that magnetosheath jets—similar to those observed at Earth—can also occur at comets. We explore the role of waves for the generation of magnetosheath jets within cometary magnetospheres.
How to cite: Moeslinger, A., Gunell, H., Fatemi, S., and Götz, C.: Hybrid simulations of large-scale plasma waves at comets and their connection to magnetosheath jets, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18530, https://doi.org/10.5194/egusphere-egu26-18530, 2026.
Martian space is rich in plasma waves generated by plasma instabilities in both the solar wind and the Martian environment. These waves interact with charged particles through wave–particle interactions, leading to the acceleration, heating, and scattering of particles. Such processes further influence the kinetic evolution of charged particles and cause variations in their spatial and energy distributions. Magnetosonic (MS) waves, a type of electromagnetic wave driven by proton ring-beam distributions, propagate nearly perpendicular to the background magnetic field with frequencies ranging from the proton gyrofrequency to the lower hybrid frequency. Based on their distinct origins, MS waves in Martian space can be categorized into two types: solar wind-originated MS waves and magnetosphere-generated MS waves, which can be distinguished by their frequency characteristics due to differences in the ambient magnetic field.
Using data from NASA’s MAVEN spacecraft collected between October 2014 and May 2023, we statistically analyze the occurrence rates and wave properties of both types of MS waves in Martian space. The results reveal that solar wind–originated MS waves exhibit higher occurrence rates (~27.6%) downstream of the dayside magnetic pileup boundary, with enhanced occurrence on the dusk side compared to the dawn side. These waves show larger amplitudes on the dayside, reaching maximum average values of ~2.5 nT. In contrast, magnetosphere-generated MS waves are preferentially observed in the nightside magnetic pileup region and particularly in the magnetotail (~8%), with a tendency toward the dawn side. Waves located within the Martian magnetosheath show amplitudes of approximately 0.5 nT. Further analysis indicates that increasing solar wind dynamic pressure significantly enhances the occurrence of solar wind-originated MS waves near the bow shock, in the magnetosheath, and in the magnetotail, while also increasing the occurrence of magnetosphere-generated MS waves in the magnetotail. With increasing solar EUV flux, the occurrence of solar wind-originated MS waves slightly increases in the magnetotail, whereas magnetosphere-generated MS waves increase markedly. Both types of MS waves are rarely observed in regions strongly affected by crustal magnetic fields, and their spatial distributions expand with altitude.
In summary, solar wind-originated MS waves exhibit higher occurrence rates and larger amplitudes overall. The spatiotemporal distribution characteristics of MS waves in Martian space provide important insights into their generation mechanisms, propagation behaviors, and wave-particle interaction processes. Moreover, an interesting case of simultaneous observation of solar wind-originated and magnetosphere-generated MS waves was identified. In this event, proton motions seem to be influenced and possibly modulated by solar wind-originated MS waves, and preliminary analyses of this wave event reveal additional intriguing features.
How to cite: Pang, S., Fu, S., Ni, B., Yun, X., Jin, T., and Du, H.: Statistical Distribution of Magnetosonic Waves in the Martian Space, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17523, https://doi.org/10.5194/egusphere-egu26-17523, 2026.
Although Earth’s Moon lacks a collisional atmosphere, it is known to possess a surface-bounded collisionless exosphere populated by volatile species undergoing thermally-driven ballistic jumps across the surface. Previous models of the lunar exosphere have focused primarily on atomic species (e.g. H, Ar, etc.), with water, hydroxyl (OH), and H2 being the only molecular species that have received significant attention.
However, these are not the only volatile molecular species that exist on the Moon. The LCROSS impactor uncovered a diverse population of volatile species within one of the Moon’s polar permanently-shadowed regions, of which water was the most abundant. Here, we model the exospheric ballistic transport of two sulfur bearing species (H2S and SO2), that were measured in the LCROSS impact plume at abundances of 16.75% and 3.17% relative to water, respectively. As a key component in our model, we use molecular dynamics simulations to determine the surface binding energy distributions of these two species on lunar-like surfaces.
How to cite: Hayes, D., Verkercke, S., Morrissey, L., and Moores, J.: Examining the Ballistic Transport of Sulfur-Bearing Volatile Species in the Lunar Exosphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12859, https://doi.org/10.5194/egusphere-egu26-12859, 2026.
Hot Flow Anomalies (HFAs) are common transient structures in the foreshock region, generated by interactions between solar wind discontinuities and planetary bow shocks. Owing to the scarcity of multi-spacecraft observations at other planets, the evolution of HFAs has only been confirmed near Earth. Using joint observations from the Mars Atmosphere and Volatile EvolutioN (MAVEN) and Tianwen-1 missions, we investigate the evolution of a Martian HFA. This HFA was detected first by MAVEN on the dayside, and later observed by Tianwen-1 on the nightside. The HFA’s core region exhibits negligible magnetic fluctuations, with little change in thickness during propagation, while the peak magnetic field magnitude at its trailing edge decreases a lot. Notably, this HFA remains a young-type HFA and does not evolve from the ‘young’ to ‘mature’ type. This indicates that due to the small size of Martian bow shock, HFAs formed upstream of the quasi-parallel shock can rapidly propagate to the quasi-perpendicular shock region, precluding continuous injection of shock-reflected ions.
How to cite: Wang, H., Wu, M., and Zhang, T.: The Evolution of Hot Flow Anomalies in Martian Space Environment, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6266, https://doi.org/10.5194/egusphere-egu26-6266, 2026.
Venus lacks an intrinsic magnetic field, and its induced magnetosphere differs significantly from Earth's stable dipolar magnetic field. Although magnetic reconnection was detected in the near Venusian magnetotail, the drivers and impacts of magnetic reconnection at Venus remain poorly understood. In this study, we present the global magnetohydrodynamic simulation of Venusian magnetotail reconnection. The results reproduce characteristic reconnection signatures in the Venusian magnetotail and delineate the formation of three-dimensional magnetic structures consistent with reconnection topologies. We demonstrate that reconnection is triggered by the compression of the draped interplanetary magnetic field following an interplanetary shock, a mechanism previously associated with terrestrial dynamics. We further explore the roles of velocity, density and magnetic field of the solar wind in this process. This work highlights new insights into magnetic reconnection in unmagnetized plasma environments.
How to cite: Meng, Z., Tong, D., Jiuhou, L., Binzheng, Z., Rongsheng, W., Sudong, X., Tielong, Z., Junjie, C., and Maodong, Y.: Shock-induced magnetic reconnection in the Venusian magnetotail, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15406, https://doi.org/10.5194/egusphere-egu26-15406, 2026.
As comets journey through the solar system, ices on the surface sublimate and the released neutral gas is ionized. Thus, the comet nucleus is surrounded by a cloud of heavy ions and electrons that interact with the solar wind. Their environment therefore is a unique laboratory to study plasma pick-up processes and multi-ion plasmas. In turn, remote observations of comets with imaging telescopes on ground and in space provide information about the solar wind properties at the comet. Comets are therefore laboratory and measurement at the same time. Studying the impact of solar wind structures like corotating interaction regions and interplanetary coronal mass ejections can therefore inform our knowledge of the processes in a collisional plasma. Active comets have a highly disturbed bow shock that can give rise to a number of cometosheath structures, one of which are magnetospheric jets: regions of enhanced dynamic pressure in the magnetosheath. They are usually associated to the region behind a quasi-parallel shock and have been well documented at Earth.
However, in recent years there have been efforts to identify these structures in other magnetosheaths as well. For example, recently it has been shown that they exist in the Martian magnetosheath. As the cometary plasma environment has very similar characteristics as the Martian one, it stands to reason that these structures also exist at Comets.
We present a study that uses Rosetta magnetic field, density and ion measurements to identify possible jet structures.
We find that they are ubiquitous especially in the plasma environment where Rosetta is probably in the cometosheath. Their occurrence matches what was found for similar events at Mars. The magnetic field can correlate or anti-correlate with the density enhancement, just like it is observed at Earth and Mars. Although velocity data is limited, at least some of the events show a velocity increase in the cometary ion population. This could be the first detection of a magnetosheath structure in the non-solar wind component of the plasma.
How to cite: Götz, C., Doyle-Morgan, R., Gunell, H., Krämer, E., Karlsson, T., Möslinger, A., Simon-Wedlund, C., and Volwerk, M.: Possible detection of magnetosheath jets in the environment of comet 67P/Churyumov-Gerasimenko, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5797, https://doi.org/10.5194/egusphere-egu26-5797, 2026.
Many different kinds of waves occur in the ionised coma of a comet, and these waves span a wide range of temporal and spatial scales. For example, ESA's Rosetta spacecraft, which spent to years near comet 67P/Churyumov-Gerasimenko from 2014 to 2016, detected singing comet waves, steepened magnetosonic waves, ion Bernstein waves, ion acoustic waves, and lower hybrid waves.
Using data from the Rosetta Plasma Consortium of the Rosetta mission, we present a study of waves near the electron plasma frequency that we identify as Langmuir waves (Gunell et al. 2025, doi:10.1051/0004-6361/202555043). These Langmuir waves were observed when the comet was near perihelion. During this period a diamagnetic cavity had developed around the nucleus, and outside this cavity steepened magnetosonic waves were observed. Significant Langmuir wave activity was detected only in the environment outside the diamagnetic cavity, where simultaneously the steepened magnetosonic waves were observed. We suggest a possible generation mechanism for the Langmuir waves and a scenario through which energy can be transferred from the large and slow scale of the steepened waves to the small and fast scales of the Langmuir waves.
How to cite: Gunell, H., Stenberg Wieser, G., Möslinger, A., Götz, C., Canu-Blot, R., and Henri, P.: Langmuir Waves at Comet 67P: Rosetta Observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6875, https://doi.org/10.5194/egusphere-egu26-6875, 2026.
Measurements by the Langmuir Probe (LAP) onboard Rosetta around the perihelion passage of comet 67P/Churyumov–Gerasimenko showed an approximately 50% attenuation of the solar extreme-ultraviolet (EUV) radiation. This has been suggested as indicative of grain fragmentation in the cometary coma. Using simple analytical models we examine requirements on the fragmentation behavior to explain the observationally inferred level of EUV attenuation. Our results are in line with [1]; suggesting that in order to match the LAP observations, a significant fraction of the dayside dust population must disintegrate to fragments of sizes of several tens of nanometers within a few thousand kilometers from the nucleus.
[1] F. L. Johansson et al. 2017, MNRAS, 469, 626
How to cite: Vigren, E., Johansson, F. L., Edberg, N. j. T., and Eriksson, A. I.: Requirements on grain fragmentation to explain extensive solar EUV attenuation in the coma of comet 67P/Churyumov-Gerasimenko near perihelion, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12090, https://doi.org/10.5194/egusphere-egu26-12090, 2026.
Plasma density observations from the Rosetta Plasma Consortium reveal two distinct physical regimes for the ion dynamics in the coma of comet 67P/Churyumov-Gerasimenko. At lower rates of outgassing when the Rosetta spacecraft was close to the cometary nucleus, ions moved with the neutral gas background; at higher rates of outgassing, a diamagnetic cavity formed, and the observed plasma density attested to ion acceleration with respect to the background neutral gas. The diamagnetic cavity was detected around perihelion from April 2024 to February 2016. The end of this period corresponds to the transition between the two regimes, as the comet moved away from the Sun, outgassing decreased and Rosetta got closer to the cometary nucleus.
Current global 3D plasma models of the cometary ionosphere underestimate observed ion number densities during the low outgassing regime. A simple radial model lacking acceleration better explains Rosetta plasma observations. In order to identify the cause of the underestimation by the current global plasma model, we assess the sensitivity of the cometary ion dynamics to several parameters during the transition. For that purpose, we use our in-house 3D ion test particle model driven by the fields generated by a hybrid model. First, we assess the sensitivity of the ion dynamics to collisions between the ions and the neutral background. This process is not sufficient to explain the discrepancy. Next, we evaluate the sensitivity of the ion dynamics with electron temperature through the ambipolar electric field. Current models assume adiabatic electron behavior; however, electrons trapped close to the cometary nucleus by the ambipolar field are collisional, not adiabatic, and the resultant cooling feeds back to weaken the ambipolar electric field. We show that the resulting simulated plasma density is affected by the use of a more realistic electron temperature profile derived from electron test particle modelling, bringing it closer to the Rosetta plasma density.
How to cite: Steinwand, V., Stephenson, P., Lewis, Z., Kallio, E., Beth, A., and Galand, M.: Cometary ion dynamics under weakly outgassing conditions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5705, https://doi.org/10.5194/egusphere-egu26-5705, 2026.
The interaction between planetary atmosphere and stellar winds governs atmospheric evolution in unmagnetized planets. Generally, interplanetary magnetic field (IMF) drapes around the planetary ionosphere, creating a magnetic barrier that deflects stellar winds and leads to the formation of an induced magnetosphere. However, whether an induced magnetosphere can form under radial IMF conditions where the IMF aligns with solar wind flow in our solar system remains controversial. By analyzing joint observations from the Tianwen-1 orbiter and the Mars Atmosphere and Volatile Evolution mission combined with hybrid numerical simulations, we clearly demonstrate the formation of Mars’ induced magnetosphere during the radial IMF for the first time. This induced magnetosphere comprises draped magnetic field and induced magnetic field. Magnetic pressure buildup above the ionosphere surpasses incident solar wind pressure, which establishes a stable magnetic barrier. This finding indicates that the draped magnetic field still forms under radial IMF. The formation of Mars’ induced magnetosphere under the radial IMF could be a general pattern for the interaction between the IMF and planetary atmosphere, which can be referred to terrestrial exoplanets within the close-in habitable zone of dwarf stars. This work clarifies the fundamental understanding of solar wind interactions with unmagnetized planets across diverse solar wind conditions.
How to cite: Lin, R., Zhou, J., Huang, S., Wang, Y., Dubinin, E., and Fränz, M.: Observations and hybrid simulation of Mars’ induced magnetosphere under radial interplanetary magnetic field, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2521, https://doi.org/10.5194/egusphere-egu26-2521, 2026.
Observations of the Martian upper atmosphere over the past several decades, from both Earth-based telescopes and Mars-orbiting spacecraft, have revealed a highly dynamic system strongly influenced by solar forcing. Variability driven by space weather events such as solar flares, solar energetic particle (SEP) events, and coronal mass ejections (CMEs) plays a crucial role in controlling the structure, composition, and escape of the Martian atmosphere. However, important uncertainties remain regarding the magnitude, altitude extent, and temporal evolution of these responses.
A major advance in our understanding of the Martian upper atmosphere and its plasma environment is expected from M-MATISSE, an ESA Medium-class mission candidate currently in Phase A. The M-INEA instrument, a neutral and ion mass spectrometer within the M-EPI plasma suite onboard M-MATISSE, is designed to investigate the coupling between neutrals, ions, and the solar wind, and to quantify processes leading to atmospheric escape.
In support of defining the scientific requirements of M-INEA, we use the observations from the Neutral Gas and Ion Mass Spectrometer (NGIMS) onboard the MAVEN spacecraft. We characterize the response of the Martian upper atmosphere and ionosphere on short- and long-term variations during selected space weather events. The analysis focuses on identifying typical variability levels, event-driven enhancements, altitude dependence, and orbit-to-orbit variability, providing constraints on sensitivity, dynamic range, and temporal resolution required for future measurements.
How to cite: Mukundan, V., Millio, A., Mangano, V., Leblanc, F., Felici, M., Stumpo, M., and Benna, M.: Martian upper atmospheric variability observed by MAVEN/NGIMS in response to space weather events in view of M-MATISSE mission, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9878, https://doi.org/10.5194/egusphere-egu26-9878, 2026.
Ultra-low frequency plasma waves at a local ion gyrofrequency have been detected upstream of the bow shock at every planet with an extended atmosphere. These waves are observed as left-hand elliptically polarised, propagating mostly parallel to the ambient interplanetary magnetic field. They originate from solar wind pickup of ionised exospheric neutrals, especially H+, for which they are called Proton Cyclotron Waves (PCWs), and depend on the cone angle between the solar wind flow and the magnetic field. Excluding the foreshock, the wave analysis provides constraints for the exospheric species density at the origin of the waves. Using 10 years of magnetometer measurements from MAVEN, we show at Mars how the wave occurrence rate and inferred neutral densities evolve with solar longitude and solar wind cone angle. This method is used to extend to other masses than hydrogen, such as mass 2 (D, H2), and we discuss the consequences of our results on Mars’ planetary atmospheric evolution.
How to cite: Simon Wedlund, C., Weichbold, F., Mazelle, C., Schmid, D., Lammer, H., Scherf, M., Volwerk, M., Meziane, K., Bertucci, C., Halekas, J., Espley, J., Curry, S., and Temmer, M.: Characterising Mars’ extended hydrogen exosphere from waves at the local ion cyclotron frequency, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12934, https://doi.org/10.5194/egusphere-egu26-12934, 2026.
M-MATISSE is one of the three mission candidates for the ESA M7 science mission call, all currently in Phase A with selection of the mission planned in the middle of 2026 and a possible launch at 2037. The M-MATISSE mission involves two spacecraft (Henri and Marguerite) with almost identical scientific payload to investigate the Mars plasma environment, its response to space weather, and its link with the atmosphere of the red planet. The proposed M-MATISSE configuration involves six scientific instruments on both spacecraft, two of them being consortia of several scientific sensors with common data processing units.
The Solar Particle at Mars (SP@M) experiment is a part of the Mars Ensemble of Particle Instruments (M-EPI) suite of three particle sensors. SP@M will study the energy and angular distributions of 30 keV to 1 MeV electrons and 30 keV to 10 MeV ions with 4 electron and 4 ion telescopes per spacecraft. This presentation will describe the design of SP@M as achieved at the end of Phase A, ongoing development activities including digital signal processing, electron-ion discrimination, and analysis of the performances of a prototype with numerical simulations and irradiation campaigns. The scientific objectives of SP@M will also be presented, including the added value of having for the first time at Mars two observatories of suprathermal and energetic particles.
How to cite: Nenon, Q., Devoto, P., André, N., Thomas, V., Prech, L., and Nemec, F.: Solar energetic particle instrument SP@M for ESA M7 mission candidate M-MATISSE, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6606, https://doi.org/10.5194/egusphere-egu26-6606, 2026.
Planetary bow shocks are sites where a fraction of the solar wind is accelerated to suprathermal energies. In the terrestrial foreshock, sunward propagating ion beams of several keV collimated along the interplanetary field lines (Field-Aligned Beams) are usually observed within a region upstream from the quasi-perpendicular shock. Numerous observations indicate that these beams are not seen along IMF lines that make an angle larger than 70o with the local shock normal (θBn), thereby marking the spatial location of the ion foreshock boundary. The ion foreshock boundary reflects the maximum level of energization that solar wind ions can reach via coherent interaction with a planetary shock. In the present study, the Martian ion foreshock boundary is investigated for the first time using MAVEN particle and magnetic field data. More than fifty spacecraft orbit segments were scrutinized to identify the presence of FAB events. The shock geometry associated with each FAB event was determined using a bow shock model. The obtained results clearly indicate that no FAB is observed for a shock-θBn larger than 51o. Our results indicate that the Martian ion foreshock boundary is located downstream of the expected location based on the terrestrial case. This finding is in good agreement with a recent report showing that FABs observed in the Martian foreshock have noticeably lower speeds than those observed at Earth. The characteristics of both the terrestrial and Martian ion foreshock boundaries provide new and relevant insights into the mechanisms responsible for FAB formation at planetary bow shocks. Furthermore, the present results point to a spatial boundary where ultra-low frequency waves excited by the beams are found.
How to cite: Meziane, K., Mazelle, C., Hamza, A., Simon-Wedlund, C., Bertucci, C., Halekas, J., Mitchell, D., Espley, J., and Curry, S.: The Martian Ion Foreshock Boundary, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11760, https://doi.org/10.5194/egusphere-egu26-11760, 2026.
Ion escape constitutes one of the key processes driving Martian atmospheric evolution, and the magnetotail serves as a crucial channel for ion escape from Mars. Based on 10-years in-situ magnetic field and particle data obtained by the MVAEN satellite, we selected 220 Martian magnetotail current sheet crossing events that satisfy the 1-D Harris current sheet model. Through systematic statistical analysis of ion flux and density in the current sheet and tail lobe regions, we clarified the ion distribution characteristics in these two regions. Furthermore, combined with the induced magnetosphere boundary model, we calculated the escape rates of various ion species in the current sheet and tail lobe regions, and investigated the effect of solar wind conditions on the magnetotail ion escape process.
How to cite: Wu, M., Lv, Q., and Zhang, T.: The ion escape rate in the Martian magnetotail, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6204, https://doi.org/10.5194/egusphere-egu26-6204, 2026.
The Mars foreshock is populated by backstreaming particles that can generate a variety of foreshock transients and plasma waves. Using observations from Mars Atmosphere and Volatile EvolutioN (MAVEN) mission on 4 March 2018, we report a clear electron heating associated with a spontaneous hot flow anomalies (SHFAs) at Mars, accompanied by lower hybrid waves in the core region and a 1 Hz wave at the compression region. In the SHFA core region, the observed electron heating involves both adiabatic and non-adiabatic acceleration processes. In addition, the LHWs likely contribute to electron heating along the magnetic field and modulate both the electron energy flux and density. Within the compression region, the 1 Hz wave can efficiently scatter electrons, resulting in electron pitch angle distributions that become more isotropic. These results provide new insights into electron heating and the kinetic-scale wave-particle interactions associated with the SHFAs at Mars.
How to cite: Chen, Y., Wu, M., and Zhang, T.: Electron Heating Associated with Spontaneous Hot Flow Anomaly at Mars, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6282, https://doi.org/10.5194/egusphere-egu26-6282, 2026.
Venus and Mars, lacking global intrinsic magnetic fields, form induced magnetotails through their interactions with the solar wind. These regions exhibit dynamic magnetic field structures and turbulent fluctuations that play a key role in mediating energy dissipation and ion escape. While both planets form induced magnetospheres via the draping of interplanetary magnetic field lines around their ionospheres, differences in planetary parameters such as ionospheric conductivity, planetary size, and the presence of crustal magnetic fields on Mars may lead to distinct turbulence characteristics in their magnetotails. Using in situ observations from multiple spacecraft missions, we perform a systematic comparison of magnetic turbulence, magnetic field topologies, and associated current systems in the induced magnetotails of Venus and Mars. We characterize the spectral properties of magnetic fluctuations and examine their correlations with large-scale magnetic configurations. Our analysis reveals how turbulence modulates energy and mass transport in the magnetotails of Venus and Mars, providing insights into the comparative evolution of their space environments and atmospheric loss processes.
How to cite: Xiao, S.: Turbulent Magnetic Field Environments in the Induced Magnetotails of Venus and Mars, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9923, https://doi.org/10.5194/egusphere-egu26-9923, 2026.
Venus is a terrestrial planet comparable to Earth in size and orbit, but it lacks a global magnetic field and has a markedly different atmosphere. Due to relatively sparse observations and limited modeling capabilities, the fine meso-scale structures have not received enough attention, despite their key roles in cross-scale momentum and energy coupling as well as atmospheric escape. In this study, we present the development of a high-resolution MHD model of the magnetosphere–ionosphere system for unmagnetized planets. Using both simulations with observations, we investigate fine structures in the space environments of Venus, including Kelvin–Helmholtz instability, turbulence, and ion escape. The results provide new insights into multiscale coupling and the evolution of the unmagnetized planetary environments.
How to cite: Dang, T., Lei, J., Zhang, B., Zhang, T., Xiao, S., and Chen, J.: Unveiling the fine structures of Venusian space environment: Kelvin-Helmholtz Instability and Turbulence, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11863, https://doi.org/10.5194/egusphere-egu26-11863, 2026.
Electromagnetic waves at the local proton cyclotron frequency are frequently observed upstream from the Martian bow shock. They are excited by unstable velocity distributions of newborn protons continuously produced locally by ionization of exospheric hydrogen atoms (pickup protons). The analysis of MAVEN magnetic field data demonstrates for the first time that the amplitude of these waves undergoes a sharp gradient when crossing the electron foreshock boundary. Moreover, a decrease of the amplitude with the increasing distance from the shock along the ambient magnetic field is observed inside the foreshock. Both signatures are correlated with the variations of the energetic electron fluxes. These two properties connecting the wave growth to electron physics raise an issue since the waves are excited purely through an ion-ion instability. We propose that the extra free energy necessary to increase the wave amplitude be due to additional ionization of hydrogen atoms by electron impact ionization inside the foreshock. These results imply that extreme caution is needed when directly deriving the exospheric densities at Mars and other similar environments from the local pickup ion wave amplitude, especially in the foreshock region.
How to cite: Mazelle, C., Meziane, K., Simon-Wedlund, C., Bertucci, C., Romanelli, N., Zhang, C., Frutchman, J., Halekas, J., Mitchell, D., Espley, J., and Curry, S.: Foreshock Electrons Impact Ionization Effect on the Amplitude of Pickup Proton Generated Waves: Consequence on Exosphere Density Determination, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8155, https://doi.org/10.5194/egusphere-egu26-8155, 2026.
As a body without a thick atmosphere or global magnetic field, the Moon is directly exposed to incident ion fluxes from the solar wind and the terrestrial magnetosphere. As ions strike the lunar surface, they sputter individual regolith atoms, thereby contributing one component of the lunar exosphere. Previous work has studied the lunar sputtered exosphere during both nominal solar wind conditions and extreme space-weather activity such as coronal mass ejections (CMEs). These studies have suggested greater-than-tenfold increases in the lunar exospheric density during CME events due to elevated sputtering rates. Here, we analyze the effects that CMEs may have on the production and equilibrium of the sputtered neutral exosphere at the Moon via the use of in-situ solar wind measurements during CMEs. In particular, we investigate the role that heavy, highly charged minor ions in the solar wind may play during CME impacts at the Moon.
For this purpose, we use measurements of the plasma moments and heavy ion composition during CMEs observed by the ACE/SWICS instrument at Sun-Earth L1 over the period of 1998–2011. We extract the solar wind flux and heavy ion composition during the event intervals listed in the publicly available “Richardson and Cane CME list” and convolve the heavy ion fluxes with appropriate sputtering yields for the lunar regolith. Generally, we find that solar wind heavy ions nominally contribute ~5% of the total sputtering yield while extreme events can reach contributions of ~20%. In no cases, however, do solar wind minor ions dominate the sputtering rates at the Moon. Finally, we discuss the implications of this work for our understanding of the full variability of the Moon’s exosphere.
How to cite: Poppe, A. R., Nénon, Q., Szabo, P. S., Carberry Mogan, S. R., and Lee, C. O.: Assessing the effects of coronal mass ejections on the sputtered lunar exosphere: the role of solar wind minor ions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7882, https://doi.org/10.5194/egusphere-egu26-7882, 2026.
