The Io Plasma Torus (IPT) plays a key role in the workings of the Jupiter System at large. It is a complex system driven by Io’s volcanism and surface-atmosphere that interacts with numerous Jupiter System objects. Despite significant and varied modelling efforts, the description of its spatial structure and temporal variability remains challenging, especially because of insufficient data coverage.In this EGU Poster, we analyze the IPT's spectral emissions and spatio-temporal dynamics to establish the optical specifications for a future ground-based observation system. Our main conclusions are as follows:1- Temporal variability: the large diversity of objects in the Jupiter System with which the IPT interacts, and the complex, highly non-linear nature of these interactions, contribute to the strong observed temporal variability of the IPT, which displays a broad range of time scales, from hourly to multi-decadal. Capturing all timescales requires hourly, intercalibrated observations, necessitating dedicated space platforms and/or a longitudinal ground network.2- Spatial scales: the Io system includes interconnected objects of very different spatial extensions, from tens of km with Io’s volcanoes and plumes, to more than 1000 Rj with the nebula(e). Hence, an observation system covering the Io system in a comprehensive way will need to combine observations with very diverse spatial coverages, from sharp AO observations (e.g. 0.02’’ achieved with the LBT) to 5.5°.3- Spectral extension: electromagnetic emissions generated by the Io system cover a very large part of the electromagnetic spectrum, and the different components of the system emit to a large part in different wavelength ranges and in the different spectral lines corresponding to different neutral and ionized species. Hence, a combined set of telescopes covering this system in a comprehensive way will have to optimally combine observations of different spectral lines in different spectral ranges. 4- Complementary observations: beyond the body of UV / EUV observations from space, ground-based observations over the last 50 years have also borne very valuable fruit. Indeed, instrumentation necessary to image the IPT does not necessarily need to be expensive: simple designs using smart "amateur-class" equipment already allow for the observation of the brightest lines. As spaceborne and ground-based observations offer complementary advantages and limitations, a future comprehensive observation system for the IPT will likely have to combine both.Given stringent time resolution constraints, and aiming at an affordable budget envelope, the development of a longitudinal network of telescopes appears as particularly cost-effective and promising. It could build on the successful IPT telescopes that already exist in different longitude sectors and complement them with one or several ones at key locations, including the European and African sectors. In France, such an effort will be coordinated at the national level, allowing one to take full advantage of synergies between radio observations at Nançay and new optical observations. In this poster, we outline design guidelines for a smart, multi-site, multi-spectral system capturing the IPT's spatiotemporal dynamics and coupling processes that will address the choice of telescope as well as of the spatial (coronagraph) and spectral (color filters) filtering systems.

Thanks to MESSENGER observations, we know that Mercury’s magnetosphere is highly dynamic, and it can be fully reconfigured in a few minutes, with strong influences of external conditions.BepiColombo mission includes a comprehensive payload for the investigation of the environment. During the swing-bys the magnetic field and particles in Mercury’s magnetosphere were successfully measured by the MPO and Mio payloads. In this presentation, we will focus on Mercury’s swing-by 2 (MSB2) on 23 June 2022 showing a good example of highly dynamic magnetosphere.During this swing by, BepiColombo passed from dusk in the far tail toward dawn in the dayside. The trajectory was in the southern hemisphere in a nearly equatorial path. Simultaneous Na ground-based observations have been obtained by the THEMIS solar telescope during the whole day. Solar Orbiter was at about 90° est of BepiColombo observing the Sun remotely.These two simultaneous observations allowed to observe the magnetosphere in situ while the Na global exosphere was imaged.According to the magnetic field data (MPO-MAG and MGF) before and after the flyby, the IMF z component was around 0 nT varying between northward to southward. The solar wind observed by SERENA-PICAM before and after the swing-by shows a high variability in the energy. Ion and electron populations in the plasma sheet and close to the planet at dawn have been observed.When the spacecraft was entering in the far tail at about 9 UT, an abrupt increase in dayside exospheric intensity has been registered by THEMIS. This intensity slowly recovered to the previous values in about 3 hours. When the spacecraft exited from the planetary shadow, at 9:50 UT, SIXS-P observed an electron population at energy between 70-280 keV.The magnetopause boundary was clearly identifiable together with a weak low latitude boundary layer. While the bow shock crossing was not clearly distinguishable, showing energy-dispersion signatures and a flapping boundary. Upstream the bow shock, foreshock ions have been observed by SERENA-PICAM and MPPE-MSA in agreement with a quasi-parallel IMF configuration.On the same day, Solar Orbiter/FSI observed a M2 and long-lasting flare from 9:00 UT to 12:UT in the southern solar hemisphere toward Mercury quadrant.While the Na exospheric variability is clearly linked to solar conditions, it is still difficult to describe the exact mechanism responsible of the Na release without two vantage-point measurements providing information of external conditions and magnetospheric dynamic and exosphere.

Abstract. The Jovian Energetic Neutrals and Ions (JENI), part of the Particle Environment Package (PEP), on the Jupiter Icy Moons Explorer (JUICE) spacecraft is a state-of-the-art detector, capable of analyzing the energy and direction of incident Energetic Neutral Atoms (ENAs) from planetary magnetospheres. Our analysis focuses on 2.86–85.5 keV Hydrogen ENA measurements between 21 to 24 August 2024 when JUICE performed the Lunar and Earth Gravity Assist (LEGA). During the LEGA, JENI had a unique opportunity to obtain continuous, 7.5-minute accumulation time global images of the terrestrial magnetosphere as the spacecraft moved outward from ~17 to 150 Earth Radii. Although there were no indications of substantial geomagnetic storms developing during that time, substorm activity was observed based on eight distinct dips of the SuperMAG AL (SML) index down to ~-250 nT for the four last ones and even down to ~-400 nT for the four first ones. Our results indicate increased ENA emissions associated with the onsets of these events, suggesting direct responses to the increased energetic ion activity during those substorm events. Unlike the periods of intense geomagnetic storms, during which proton intensities build up the ring current evolving from an asymmetric distribution during the main phase to a roughly symmetric distribution during the recovery phase, the images from JENI during this interval show non-uniform ENA emissions in the plasma sheet, suggesting transient processes, such as a series of repeated nightside injections. The nightside ENA intensities are generally brighter than those from the dayside, possibly reflecting magnetotail processes associated with energetic ions being injected.

Electron radiation belts, reservoirs of stably trapped energetic electrons hazardous to space technology, are a prevalent feature of most magnetized planetary environments. However, their existence in the compact magnetosphere of Mercury has been a subject of debate for decades. The presence of energetic electrons was first identified by Mariner 10’s observations in the 1970s but was subsequently questioned by MESSENGER’s limited energetic particle measurements 40 years later. Here we integrate MESSENGER’s more sensitive indirect energetic electron measurements with new analysis techniques, particle simulations and theory to discover a structured radiation belt with a variable morphology subject to solar wind activity. This radiation belt can persist for several Earth days and, thus, seems to be quasi-permanent under weak solar wind forcing. However, it becomes unstable under strong driving as electron drift orbits bifurcate about the magnetic equator within the dayside magnetosphere and particles are rapidly lost. Our results establish that even compact magnetospheres can host radiation belts and, furthermore, that Mercury is a natural laboratory for radiation-belt physics usually inaccessible at Earth: one of an extreme, rapidly driven state. Mercury is found to host a radiation belt under weak solar wind driving that becomes unstable during strong forcing, providing insights into energetic particle dynamics in an extreme planetary environment.

Abstract. During the first Earth gravity assist maneuver of JUICE on 20th August 2024 the spacecraft passed through the Earth plasmasphere for about 2 hours. Before closest approach at a distance of 2.1 RE the Jovian Electron and Ion spectrometer JEI of the PEP instrument suite was switched on for 40 min in an ion mode test configuration. The high plasma density of about 3000/cm3 (observed by the RPWI plasma wave instrument) led to a negative charging of the spacecraft which allowed a rare observation of the cold and dense plasmaspheric ion populations. Since the ions are only corotating with the Earth at a velocity of about 1 km/s at this distance the observed ion speed is dominated by the spacecraft velocity of about 8 km/s. For this reason ions with different mass appear at different energies in the energy spectrum observed by the JEI sensor. In addition the spacecraft potential leads to specific filtering of ion masses in the observed angular distribution. By calculating the sensor response function for these specific observing conditions it is possible to quantify densities of the different ion species. But this response calculation depends critically on the response of the JEI channel electron multipliers to the ion velocity and mass. Since the sensor was operated with a low post-acceleration further laboratory calibrations may be needed for this specific setup. Still we can already conclude from the observations that ions with mass >4 amu/q contribute at least 30 % to the observed total ion density. A flux peak observed in the energy spectrum at 15 eV can only be explained by the presence of heavy molecular ions with mass ~30 amu/q. Molecular ions have only been rarely detected in the outer Earth plasmasphere. The observations indicate that the JEI sensor can also be used to achieve ion composition measurements in the exospheres of the Jovian moons.

Interplanetary coronal mass ejections (ICMEs) cause “Forbush decreases” (FDs), which are local decreases in background galactic cosmic rays (GCRs). Even though FDs can be observed with simple particle instruments, their amplitude and shape provide physical profiles of passing ICMEs. However, in some cases, previous statistical studies of the heliocentric distance dependence of FD changes associated with ICME propagation have found no strong correlation. We need the criteria for evaluating the relationship between ICME structure and FDs, necessary for the FD’s statistical analysis. This study investigates the effect of the evolution and interactions of ICMEs on FD profiles in the inner solar system using multipoint comparisons. We focus on multipoint ICME observations by Solar Orbiter, BepiColombo, and near-Earth spacecraft from 2022 March 10 to 16, when these spacecraft were ideally located for studying the radial and longitudinal evolution of ICMEs and accompanying FDs. We compared GCR variations with the multiple in situ data and ICME model, clarifying the correspondence between the evolution of each ICME structure in the radial and azimuthal directions and the depth and gradients of the FD. The radial comparison revealed decreases in FD intensities and gradients associated with the expansion of the ICME. The longitudinal difference found in FD intensity indicates longitudinal variations of the ICME’s shielding effect. These results suggest that accurate multipoint FD comparisons require determining the relationship between the observer’s position and the inner structure of the passing ICMEs.

ESA’s JUpiter ICy moons Explorer (JUICE) mission performed the world’s first Lunar-Earth flyby on the 19-20 of August 2024, successfully rerouting the spacecraft toward Venus for another gravity assist. In October and November 2025 the JUICE payload also attempted observations of the interstellar comet 3i/ATLAS. In this presentation, we focus on observations obtained from the Jupiter Energetic Neutrals and Ions (JENI) camera and the Jovian Energetic Electron (JoEE) magnetic spectrometer, which are a part of the comprehensive JUICE Particle Environment Package (PEP). The Lunar-Earth flyby brought JUICE to within ~750 km of the Moon’s surface and ~6,840 km over Earth. JUICE flew through Earth’s magnetotail visiting the plasma sheet, ring current, and radiation belt regions, before exiting the magnetosphere along the flank bringing the spacecraft back into the solar wind. JENI and JoEE made direct measurements of the energetic ions (~1 keV to several MeV) and electrons (~30 keV to 2 MeV) in those magnetospheric regions. During its outbound leg of the trajectory, JENI captures high-resolution images of Earth’s dynamical ring current. Several substorm injections of hot plasma were observed in Earth’s nightside.In the period 8-19 November was allowed to be on attempting ENA imaging of 3i/ATLAS and data will be downlinked by February 2026. In this presentation, we report on these exciting observations captured by JUICE discuss the instrument performance of JENI and JoEE.

Abstract Saturn's Kilometric Radiation (SKR) is a powerful non‐thermal radio auroral emission produced by the Cyclotron Maser Instability (CMI), which generates waves close to the local cyclotron frequency in a highly magnetized plasma from mildly relativistic electrons. The source of free energy for SKR was identified by Cassini to be the monoenergetic shell (horseshoe) distributions of 6–12 keV. Since then, Juno identified loss cone and shell distributions as the main and secondary CMI sources of free energy at Jupiter. We reanalyze Cassini measurements during SKR source crossings. We identify similar empty loss cones between 1.6 and 8.9 keV on 6 occasions alongside shell distributions. We show that loss cone distributions are unstable by computing the CMI growth rate. The amplified waves are predicted to have frequencies between 1.003fce and 1.017fce with a beaming angle close to 80°. Finally, we compare our findings with those obtained at Jupiter.

The Solar Particles @ Mars (SP@M) instrument, part of the M-MATISSE mission payload, is designed to measure solar energetic particles (electrons ranging from 30 keV up to 1 MeV and ions from 30 keV up to 10 MeV) using a compact detection strategy. Instead of conventional detector stacks, SP@M relies on a single 1.5-mm-thick silicon detector, where particle identification is achieved through pulse shape analysis (PSA). This technique exploits the dependence of signal rise time on the depth of energy deposition and charge-collection dynamics. A dedicated modeling framework combining Monte Carlo simulations and charge-transport tools was first developed to pre-dimension the prototypes. It provided first-order predictions of rise time distributions for electrons, protons, and alpha particles under the over-depletion regime. Experimental characterizations were then performed with Ba-133 and Bi-207 conversion electrons, and a tri-alpha source (Pu-239, Am-241, Cm-244), using controlled irradiation on both the junction and ohmic sides of the detector. The results show that the irradiation side has a critical impact: ohmic-side irradiation systematically yields longer and more dispersed rise times, enhancing species separation. For deposited energies above 600 keV, electrons and alpha particles are clearly discriminated, while below this threshold, the overlap prevents reliable separation at 4.0-ns sampling. These investigations demonstrate the feasibility of PSA for charged-particle discrimination in thick silicon detectors and highlight both its potential and limitations.

Abstract. This report presents an overview of the observations and performance of the Jovian Energetic Neutrals and Ions (JENI) and the Jovian Energetic Electrons (JoEE) belonging to the Particle Environment Package (PEP) onboard the Jupiter Icy Moon Explorer (JUICE) during its Lunar-Earth Gravity Assist (LEGA) 19–23 August 2024. Observations from the Lunar and Earth flybys are presented and discussed. While the environment around the Moon was very quiet, the Earth flyby presented a characteristic, nearly symmetric recovery phase ring current with adiabatically increasing energies with decreasing distance to Earth, and butterfly pitch-angle distributions (PADs) at high L-shells transitioning to distributions rounded around 90° pitch angle at lower L-shells. The electron radiational belt showed a double-structured outer zone, possibly from a fresh intensification, and the characteristic slot region created by loss through interactions with plasmaspheric hiss. On the outbound, JENI was operated as an Energetic Neutral Atom (ENA) camera and observed the energetic ions of the inner magnetosphere from 17.4 RE to 150 RE. During this period multiple intensifications were observed in the night side magnetosphere consistent with substorm injections. The LEGA observations provided useful data for further calibrating the sensors that overall showed a nominal performance.

Abstract. The Juice flyby of Earth in August 2024 gave us the first chance to evaluate the performance of the Jovian Plasma Dynamics and Composition analyzer (JDC) in environments similar to those expected at Jupiter. JDC is one of the sensors belonging to the Particle Environment Package (PEP) on the Juice spacecraft. It measures positive and negative ions as well as electrons in the energy range 1 eV/q to 35 keV/q. One of the most challenging observations at the final destination is those of the low energy ion populations in the tenuous ionospheres of Jupiter's icy moons. During the Juice flyby of Earth we discovered that the energies of the positive ions observed by JDC were not easy to interpret due to a problem with the energy sweep. Using measurements made on ground, we were able to reconstruct the observed energies and construct a new sweeping scheme that solves the problem and that will greatly improve future observations. We also used a simulation to explain the effects of the spacecraft velocity and spacecraft potential on the recorded positive ion fluxes when Juice passed through the Earth's plasmasphere. The study highlights the importance of in-flight calibrations for optimizing the scientific return. Planetary flybys give access to multiple low-energy particle populations besides the mono-energetic and highly directional solar wind.

BepiColombo, launched in October 2018, is currently en route to Mercury. Although its planned orbit insertion is set for November 2026, BepiColombo continuously gathers new measurements during Mercury flybys. Throughout the cruise phase, the two spacecraft remain docked, with Mio protected behind the MOSIF sun shield, resulting in a limited observation for many instruments. Despite of such constraints, thanks to the smaller Larmor radii of electrons, wider range of electrons (from a few eV to a few hundreds of keV) got detected during the 3rd Mercury flyby by Mercury Electron Analyzer (MEA) onboard Mio and Solar Intensity X-ray and Particle Spectrometer (SIXS) onboard the Mercury Planetary Orbiter (MPO). Both instruments show quite similar variations indicating that they are observing same populations of electrons with wider energy range, and small differences in time indicate there are time-of-flight of electrons related to the drift motion of particles in the magnetosphere. Together with Plasma Wave Investigations (PWI) onboard Mio, the possible electron accelerations and transport will be discussed.

The moon Io, the most volcanically active body in the Solar System, functions as the “energy converter” of the Jovian environment: tidal heating by Jupiter and its Galilean satellites powers intense outgassing that sustains both the neutral and plasma tori and feeds the Jovian magnetodisk via centrifugal processes. Spacecraft traversals and remote observations, from ground‐based telescopes to JAXA’s Hisaki, have revealed the Io Plasma Torus’s (IPT) intricate spatial architecture and variability across timescales from hours to decades. Yet, fully characterizing the drivers of IPT structure and magnetospheric dynamics remains an open challenge. In this respect, NASA’s Juno mission, in its highly inclined, low‑perijove trajectory, provides in situ measurements of magnetic perturbations, plasma composition and abundance, through both plasma wave and radio occultation experiments, while refining tidal‐dissipation models through gravity science. Complementarily, a future network of longitudinally distributed Earth‑based observatories will deliver continuous, global monitoring of auroral emissions and torus brightness, capturing rapid fluctuations that single‐station views cannot. The synergy of Juno’s detailed local sampling and round‑the‑clock remote surveillance promises a holistic view of source–sink interactions driving Jupiter’s magnetosphere and the Io torus.

Interplanetary coronal mass ejections (ICMEs) cause Forbush Decreases (FDs) effects, which are local decreases in background galactic cosmic rays (GCR). Even though FDs can be observed with simple particle instruments, their amplitude and shape provide physical profiles of passing ICMEs. However, in some cases, previous statistical studies of the heliocentric distance dependence of FD changes associated with ICME propagation have found no strong correlation. We need the criteria for evaluating the relationship between ICMEs structure and FD, necessary for FDs statistical analysis. This study investigates the effect of evolutions and interactions of ICMEs on FDs profiles in the inner Solar System, using multipoint comparisons. We focus on multipoint ICME observations by Solar Orbiter, BepiColombo, and near-Earth spacecraft from March 10-16, 2022, when these spacecraft were ideally located for studying the radial and longitudinal evolutions of ICME and accompanying FDs. We compared GCR variations with the multiple in-situ data and ICME model, clarifying the correspondence between the evolution of each ICME structure in radial and azimuthal directions and the depth and gradients of the FD. The radial comparison revealed decreases in FD intensities and gradients associated with the expansion of the ICME. The longitudinal difference found in FD intensity indicates longitudinal variations of the ICMEs shielding effect. These results suggest that accurate multi-point FD comparisons require determining the relationship between the observers position and the inner structure of the passing ICMEs.

On 8 January 2025, the ESA/JAXA BepiColombo mission flew by Mercury for the sixth time at an altitude of 295 km. The spacecraft took on a unique route through Mercury’s magnetic and particle environment, crossing the equator opposite the Sun on Mercury’s night side before flying over the planet’s north pole. During eclipse, in the cold shadow of the planet, as well as above the northern pole the spacecraft passed through regions where charged particles precipitate from the planet’s magnetic tail and from the solar wind towards its surface. We will detail the original electron observations obtained by the Mercury Electron Analyzer during Mercury’s sixth flyby, and compare and contrast them with electron observations obtained during previous BepiColombo flybys. All together, these new observations will provide new insights into the diversity of structures observed in these regions and the underlying mechanisms responsible for their formation and dynamics.

The magnetospheres of gas giants are characterised by their strong magnetic fields, the fast rotation of the planet and the presence of embedded active moons (Io at Jupiter, Enceladus at Saturn), releasing neutral gas and, from there, plasma in the innermost regions of the systems. Their dynamics is believed to be controlled by a balance between the centrifugal force acting on cororating plasmas trapped in the planetary magnetic field, plasma pressure gradients and magnetic forces. This balance determines the rate of outward transport of mass, angular momentum and energy and has a strong influence on the global configuration and dynamics of the magnetospheres. It results in the formation of a magnetodisk of plasma at the planetary equator, and a global outward transport of plasma from the innermost source regions to the outer magnetosphere where it is lost through magnetospheric boundaries or downtail. Until now, description of this transport has followed two different approaches in the literature. “Corotation enforcement” models focus on the description of angular momentum transport in a disk exchanging momentum with the planetary thermosphere/ionosphere via electric current systems transferring magnetic torques. They assume mass and conservation but do not explicitly describe the transport processes through the magnetodisk. On the contrary, radial diffusion models do not explicitly take into account angular momentum transport nor exchanges between the planet and the magnetospheric plasma, but they describe radial transport of mass and energy assuming a certain state of turbulence in the magnetodisk. We present a unifying approach of the radial transport of mass, angular momentum and energy, using turbulent diffusion and including sources and sinks of plasma of arbitrary radial distribution throughout the disk. Our set of coupled equations independently describes momentum exchange with the two conjugate ionospheres, thus allowing for the study of interhemispheric asymmetries, such as the ones revealed by Juno, in this coupling. We will present solutions of our coupled set of transport equations that explore the different possible causes and effects of interhemispheric asymmetries in magnetodisk/planet coupling, with emphasis on the cases of latitudinally thin and thick disks corresponding respectively to the cases of Jupiter and Saturn. We will compare the outputs of our models with recent observational constraints brought by the Juno and Cassini missions.

Jupiter's moon Callisto orbits in a highly variable magnetospheric environment depending on its position relative to the Jovian current sheet. The Juno and Galileo missions have visited the Jovian magnetosphere and crossed Callisto's orbit several times in a variety of configurations, providing an opportunity to better characterize Callisto's orbital environment. The aim of this work is to characterize the variability of Jupiter's magnetospheric environment properties at Callisto's orbit. After identifying the time intervals during which both missions crossed the moon's orbit, Juno's charged particle data from the Jupiter Energetic Particle Detector Instrument and the Jovian Auroral Distributions Experiment are combined to build composite spectra of the electron differential fluxes and derive the electron density and pressure. Based on these observations, we provide empirical models of the energy spectrum of the electron flux for different positions. The electron densities and pressures estimated from our composite energy spectra vary from 0.2 cm −3 and 0.1 nPa, respectively, at the center of the current sheet to 0.009 cm −3 and 0.004 nPa, respectively, outside. We compare these observations with those obtained by the Energetic Particles Detector onboard Galileo, which reveal an additional variation of electron fluxes with local time, possibly due to a variation of the current sheet thickness. A similar comparison of magnetic field observations with the latest magnetic field models shows a good agreement. These results can be used for studying the moon‐magnetosphere interactions in preparation for the arrival of the Jupiter Icy Moons Explorer, which will perform multiple flybys of Callisto.

Context. The interaction of the solar wind (SW) with the coupled magnetosphere-exosphere-surface of Mercury is complex. Charged particles released by the SW can precipitate along planetary magnetic field lines on specific areas of the surface of the planet. The processes responsible for the particle precipitation strongly depend on the orientation of the interplanetary magnetic field (IMF) upstream of Mercury. Aims. During the third Mercury flyby (MFB3) by BepiColombo, the properties of the SW inferred from BepiColombo observations of a highly compressed magnetosphere corresponded to those of a very dense plasma embedded in a slow SW. The Mercury Electron Analyzer (MEA) measured continuous high-energy electron fluxes in the nightside dawn sector of the compressed magnetosphere. In order to constrain further studies related to the origin of these populations, we aim to firmly confirm the initial inferences and detail the SW properties throughout MFB3. Methods. We took advantage of a close radial alignment between Parker Solar Probe (PSP) and Mercury. We monitored the activity of the Sun using SOHO coronagraphs and we used a potential field source surface model to estimate the location of the magnetic footpoints of PSP and BepiColombo on the photosphere of the Sun. We propagated the plasma parameters and the IMF measured by PSP at BepiColombo, to check if the plasma impacted Mercury. Results. We show that during MFB3, PSP and BepiColombo connected magnetically to the same region at the solar surface. The slow SW perturbation first measured at PSP propagated to Mercury and BepiColombo, as was confirmed by similarly elevated plasma densities measured at PSP and BepiColombo. The IMF orientation stayed southward during the whole MFB3. Conclusions. Our results provide strong constraints for future studies of the magnetospheric structure and dynamics during MFB3, including tail reconnection, electron and ion energization, and subsequent plasma precipitation onto the surface of Mercury.