Jamey R. Szalay

The Jovian magnetosheath plays a key role in modulating the interaction between the solar wind and Jupiter's magnetosphere. It also serves as a natural laboratory for studying fundamental plasma processes, such as turbulence, magnetic reconnection, and kinetic instabilities. Here, we introduce a data set of magnetosheath proton plasma properties derived from 9 years of Juno JADE‐I observations, including plasma density, temperature, and 3‐D bulk velocity. Covering both the equatorial dawn sector and the mid‐to‐high latitude dusk sector, the data set consists of 443 magnetosheath intervals longer than 1 hr. In total, it contains 233.2 days of observations and 317,719 data points, spanning from Juno's arrival at Jupiter to the end of the first extended mission. An overview of the data set and related statistical properties is presented to demonstrate its effectiveness and usefulness. The magnetosheath flow drapes around the magnetopause and accelerates as it moves tailward. The dawn sector plasma exhibits lower density and temperature but higher velocity than the dusk sector. These differences may result from local time effects, variations in distance from the subsolar magnetopause, and/or solar cycle modulation. This data set has strong potential to advance our understanding of Jupiter's magnetosheath through a wide range of future applications.

In this study, we propose a new mechanism to explain the observed particle flux at discrete energies in the flux tubes connecting to the wakes of the Galilean moons, first reported by Sarkango et al. (2024, https://doi.org/10.1029/2023gl107431 ) and referred to as “banded flux.” We demonstrate the proposed mechanism using test particle simulations. Sarkango et al. (2024, https://doi.org/10.1029/2023gl107431 ) propose a bounce resonance mechanism for the formation of the banded flux. However, the mechanism has not been tested numerically or analytically. In contrast, Yang et al. (2025, https://doi.org/10.1029/2024gl112240 ) propose that absorption at the moons' surfaces is responsible for the banded flux observed in the wakes of the moons. In this study, the mechanism proposed by Yang et al. (2025, https://doi.org/10.1029/2024gl112240 ) is tested using test particle simulations for the first time, and the limitations of both mechanisms are discussed. According to our proposed mechanism, the observed banded flux could result from an oscillatory parallel electric field . This is generated by the electron inertial effect in the low density region at high latitudes. The oscillatory nature of arises from multiple secondary reflections at density gradients of the Io plasma torus and the ionosphere. These reflections produce an alternating pattern with longitude and opposite polarity on either side of the M‐shell of the moon's foot point, as seen from the moon's reference frame. At a fixed location in the corotating frame, exhibits a quasi‐periodic temporal pattern.

We apply an automated routine to detect and catalog interplanetary shocks observed by the Interstellar Mapping and Acceleration Probe (IMAP). Using this catalog, we derive the upstream diffusion coefficient corresponding to 1 MeV protons along each shock’s normal direction using second-order quasi-linear theory and unified nonlinear transport theory to get the parallel and perpendicular components of the diffusion coefficient tensor, respectively. We show that the magnetic compression, as a proxy for shock strength, of fast forward shocks is statistically correlated with the upstream diffusion coefficient (Pearson correlation of 0.81 ± 0.13 and p -value of 0.014), suggesting that magnetic compression is related to the processes governing particle acceleration and particle transport near interplanetary shocks. This result is consistent with several possible interpretations, including changes in upstream turbulence, particle reflection, acceleration processes whose efficiency depends on shock compression and geometry, or a combination of these effects. We host the interplanetary shock catalog on the IMAP mission’s publicly available webpage and plan to regularly update it for use by the heliophysics community.

The inner heliosphere hosts a dynamically rich population of dust particles – the Zodiacal Dust Cloud – spanning sizes from nanometers to hundreds of micrometers and originating primarily from comets and asteroids. Over the past two decades, a generation of space missions has transformed our observational grasp of this environment. This review consolidates the advances enabled by the Wind, STEREO, Parker Solar Probe, and Solar Orbiter space missions, which together observe from heliocentric distances of 1 au down to less than 0.05 au. Two complementary observational approaches are addressed in detail. The first is in-situ dust detection via radio and plasma wave instruments, which commonly measure characteristic voltage pulses resulting from hypervelocity dust impacts on spacecraft. We describe the underlying physics, signal interpretation, dust particle mass calibration and machine-learning classification methods for this technique, which constitutes the only in-situ dust measurement capability on current inner-heliosphere missions. The second approach is remote sensing of the Zodiacal Light and F-corona through white-light coronagraph and heliospheric imagers. The combination of these approaches has yielded a consistent picture of the radial brightness profile of the cloud, provided the first observational evidence for a dust depletion zone developing sunward of 35 solar radii and a dust-free zone interior to 5 solar radii. The in-situ measurements established flux densities of dust in hyperbolic trajectories (β-meteoroids) across multiple missions, revealed variable fluxes of nanodust, and revealed solar-cycle modulation of the interstellar dust flux. This review presents these results, discusses their implications, and outlines the prospects offered by near-future missions.

Europa's sodium cloud is thought to be modified by its orbital longitude and by its plasma environment, which modulates with Jovian magnetic geometry. To explore and quantify sodium cloud variability, seven sets of Keck I/HIRES measurements are compared providing comprehensive coverage of orbital and magnetic geometry. The neutral cloud brightness and structure is more stable than past models and measurements indicate, exhibiting little correlation with orbital or magnetic longitude. The sodium cloud's apparent indifference to plasma sheet location may simply be due to smearing, since bright surface reflectance limits measurements to altitudes of several Europa radii and higher, where ballistic transport timescales are comparable to Jupiter's rotation period. The exosphere is more elongated and variable in the dawn‐dusk dimension compared to north‐south. To constrain sodium gas closer to Europa's surface, we searched for electron‐excited emission when Europa is in Jupiter's shadow and bright solar reflectance is absent. Faint emissions observed at 16 ± 11 Rayleighs are still much brighter than expected from electron impact excitation of the column extrapolated from high‐altitude sunlit spectra. This supports the view that Europa hosts a gravitationally bound sodium population close to the surface. Models of Europa's sodium cloud have broad differences in altitude structure depending on interparticle collision rates and it is unclear whether this structure is due to the velocity distribution function of sodium atoms released from the surface ice, collisional damping of hot Na with cold dense O ₂ , or a confluence of both.

Thermal electrons in Jupiter's magnetodisc have been observed to be anisotropic with higher parallel temperature compared to perpendicular. In this work, we used previously‐derived electron properties (Sarkango et al., 2025, https://doi.org/10.1029/2025gl118209 ) to calculate electron and compared the observed anisotropy with electron temperature‐anisotropy‐driven instability thresholds. For cold electrons, the ratio of perpendicular to parallel temperatures decreased with M‐shell, reached a minimum near M = 20–25, beyond which it increased until the distribution was quasi‐isotropic. In space, this turnover was observed close to the oblique electron firehose instability threshold. Linear dispersion analysis using plasma parameters representative of different M‐shells predicts the onset of the oblique firehose instability arising primarily due to cold electron anisotropy, though growth rates differ based on the cold and hot electron abundances, anisotropies, and . On the basis of these observations, we argue that the cold electron anisotropy in Jupiter's magnetodisc is regulated by the oblique electron firehose instability, which may be a source of plasma waves and could contribute to cyclotron‐resonant heating of the Jovian plasma.

Jupiter displays the brightest auroras in the solar system, driven by intensely varying energetic electrons that accelerate into the atmosphere. Here, we provide a comprehensive formalism that accurately describes the bimodality of observed auroral electron acceleration regimes. We demonstrate that the occurrence of the two dominant auroral regimes—broadband and monoenergetic—is dictated by specific characteristic plasma length scales, namely, the relationship between the transverse length scale and the electron inertial length. Furthermore, in contrast to the long-standing acceptance that Alfvén waves responsible for auroral electron acceleration exclusively originate at distant equatorial regions, we demonstrate that they can be locally generated at Jupiter’s low altitudes. From this understanding, we find that locally generated, low-altitude Alfvén waves can be directly responsible for accelerating the most intense auroral electrons at Jupiter. These findings establish that the low-altitude acceleration region can itself become a source of Alfvén waves rather than merely a sink for wave energy, thus altering the standard picture of global magnetospheric energy transfer in strongly magnetized planets.

Thermal electrons in Jupiter's magnetodisc have been observed to be anisotropic with higher parallel temperature compared to perpendicular. In this work, we used previously-derived electron properties (Sarkango et al. 2025) to calculate electron β _∥ and compared the observed anisotropy with electron temperature-anisotropy-driven instability thresholds. For cold electrons, the ratio of perpendicular to parallel temperatures (T _⊥ /T _∥ ) decreased with M-shell, reached a minimum near M=20-25, beyond which it increased until the distribution was quasi-isotropic. In T _⊥ /T _∥ -β _∥ space, this turnover was observed close to the oblique electron firehose instability threshold. Linear dispersion analysis using plasma parameters representative of different M-shells predicts the onset of the oblique firehose instability arising primarily due to cold electron anisotropy, though growth rates differ based on the cold and hot electron abundances, anisotropies, and β _∥ . On the basis of these observations, we argue that the cold electron anisotropy in Jupiter's magnetodisc is regulated by the oblique electron firehose instability, which may be a source of plasma waves and could contribute to cyclotron-resonant heating of the Jovian plasma.

We report observations of a low energy (<2 keV), trapped electron population near Jupiter's magnetic equator made by the Jovian Auroral Distributions Experiment (JADE) on Juno. Electron intensity peaks around the location of the minimum magnetic field magnitude along the field line that is connected to Juno. Pitch angle distributions peak at 90° with an average FWHM of 64°. The energy distributions have a power spectral slope of −0.74 on average with a roll‐over at ∼500 eV and a cutoff at ∼1–2 keV. There is no ordering of the peak intensity with altitude or latitude, although the peak is lower in intensity between 220° and 280° System III west longitude. There is a significant correlation between 15–70 keV ion rates and the peak electron intensity. The energy distribution of these electrons is consistent with secondary electrons created from the interaction of energetic particles with the upper atmosphere.

The inner heliosphere hosts a dynamically rich population of dust particles – the Zodiacal Dust Cloud – spanning sizes from nanometers to hundreds of micrometers and originating primarily from comets and asteroids. Over the past two decades, a generation of space missions has transformed our observational grasp of this environment. This review consolidates the advances enabled by the Wind, STEREO, Parker Solar Probe, and Solar Orbiter space missions, which together observe from heliocentric distances of 1 au down to less than 0.05 au. Two complementary observational approaches are addressed in detail. The first is in-situ dust detection via radio and plasma wave instruments, which commonly measure characteristic voltage pulses resulting from hypervelocity dust impacts on spacecraft. We describe the underlying physics, signal interpretation, dust particle mass calibration and machine-learning classification methods for this technique, which constitutes the only in-situ dust measurement capability on current inner-heliosphere missions. The second approach is remote sensing of the Zodiacal Light and F-corona through white-light coronagraph and heliospheric imagers. The combination of these approaches has yielded a consistent picture of the radial brightness profile of the cloud, provided the first observational evidence for a dust depletion zone developing sunward of 35 solar radii and a dust-free zone interior to 5 solar radii. The in-situ measurements established flux densities of dust in hyperbolic trajectories (β-meteoroids) across multiple missions, revealed variable fluxes of nanodust, and revealed solar-cycle modulation of the interstellar dust flux. This review presents these results, discusses their implications, and outlines the prospects offered by near-future missions.