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The Jovian magnetodisk plays an essential role in the dynamics of the Jupiter system by coupling its various components. Here, we investigate the Juno (JADE, JEDI, and MAG) observations of the magnetodisk within 20–80 Jupiter radii (RJ ${\mathrm{R}}_{J}$) in the 0–6 hr local time sector. JADE and JEDI data are combined to generate equatorial plane distributions of density, pressure, temperature, and anisotropy of electrons, protons, and heavy ions. Results show: (a) Heavy ions dominate both the number density and pressure. (b) The number density and pressure of all species decrease with radial distance. (c) The temperature increases for electrons and heavy ions and decreases for protons as radial distance increases. (d) On average, the parallel pressure exceeds the perpendicular pressure for all species. Based on these distributions, we explore the equilibrium and dynamics of the magnetodisk and show that: (a) Radial force balance is primarily achieved between the inward magnetic stress and the outward plasma anisotropy force. (b) An examination of the kappa parameters indicates that electrons, protons, and heavy ions primarily undergo adiabatic motion, magnetic moment diffusion, and stochastic motion, respectively. (c) A radial diffusion coefficient is derived from the radial profile of mass, providing an estimate of the timescale for radial transport from 20 to 80 RJ ${\mathrm{R}}_{J}$ of ∼ ${\sim} $ 7 hr (d) The total mass (5.0×107 $5.0\times 1{0}^{7}$ kg) and thermal energy (3.8×1037 $3.8\times 1{0}^{37}$ eV) of the magnetodisk between 20 and 80 RJ ${\mathrm{R}}_{J}$ are obtained. Key Points: Spatial distributions of the Jovian magnetodisk plasma parameters are derived from Juno/JADE+ ${+}$JEDI data during Juno's first 25 orbitsRadial force balance and radial mass transport are discussed based on these distributionsOur results provide constrains to modeling work and serve as a reference for future mission design [ABSTRACT FROM AUTHOR]

Interchange instability is known to drive fast radial transport of electrons and ions in Jupiter's inner and middle magnetosphere. In this study, we conduct a statistical survey to evaluate the properties of energetic particles and plasma waves during interchange events using Juno data from 2016 to 2023. We present representative examples of interchange events followed by a statistical analysis of the spatial distribution, duration and spatial extent. Our survey indicates that interchange instability is predominant at M‐shells from 6 to 26, peaking near 17 with an average duration of minutes and a corresponding M‐shell width of <∼0.05. During interchange events, the associated plasma waves, such as whistler‐mode, Z‐mode, and electron cyclotron harmonic waves exhibit a distinct preferential location. These findings provide valuable insights into particle transport and the source region of plasma waves in the Jovian magnetosphere, as well as in other magnetized planets within and beyond our solar system. Plain Language Summary: The radial transport of plasma around a magnetized planet is crucial for understanding the underlying magnetospheric dynamics. Jupiter's magnetospheric dynamics are primarily dominated by the rapid rotation and plasma source from Io. This rapid rotation drives the interchange instability, where hot, low‐density plasma is moved toward the inner magnetosphere. During this process, the inward moving flux tube builds up magnetic pressure, potentially leading to the trapping of particles alongside plasma waves. In this study, we present several typical examples of interchange events, and conduct a statistical analysis to explore their spatial distribution, duration and spatial extent, as well as the typical features of the associated plasma waves. This survey provides insights into mass transport, the source of these plasma waves in Jupiter's magnetosphere, with potential implications for other magnetized planets within and beyond our solar system. Key Points: Our statistical survey indicates that interchange events occur over L (or M)‐shells ∼6–26 at Jupiter with a peak occurrence rate at M ∼ 17During interchange events, various types of plasma waves are intensified, each exhibiting a distinct preferential locationThe duration and the corresponding spatial extent of interchange events are analyzed for multiple events [ABSTRACT FROM AUTHOR]

Juno performed two close flybys of Io and found enhanced field‐aligned proton fluxes are absorbed by Io. These protons are absorbed at mass input rates comparable to previous estimates for hydrogen losses from Io, hence Jupiter is likely the source of hydrogen at Io. The conditions necessary for this to occur are: (a) formation of Alfvén waves at Io, (b) wave‐particle coupling to energize protons, (c) anti‐planetward transport of ions due to the magnetic mirror force and/or parallel acceleration, and (d) strong sub‐Alfvénic interaction slowing the flow connected to Io's fluxtube allowing for sufficient travel time for energized ions to transit to Io. The derived slowdown of ≤12% the upstream value is linked to filamentation within the Alfvén wing. This mechanism is likely operating at all strongly interacting satellites and provides an avenue to transfer material from a planetary body to its satellites, including exoplanets and brown dwarfs. Plain Language Summary: Juno performed two close flybys of Jupiter's moon Io, where it observed highly directional charged hydrogen streaming along magnetic field lines. These protons hit Io and the overall influx of them is sufficient to account for previously observed proton losses from Io. Therefore, Io's protons are not from Io's interior and instead provided from Jupiter and its charged particle environment. Furthermore, the observations allow for an estimation of the speed at which plasma flows across Io, which is found to be reduced to ≤12% of the flow speed upstream from Io. These processes are likely operating at similarly interacting bodies throughout our solar system and other solar systems far from the Sun. Key Points: Io's Alfvénic interaction provides a mechanism to transport ∼10's g s−1 of Jovian hydrogen ions to Io's polesThis mechanism is a universal process that can operate at any satellite‐planet system with adequate interaction conditionsPlasma flow within Io's Alfvén wing is slowed to ≤12% of its upstream value, allowing for filamentation [ABSTRACT FROM AUTHOR]

On days 2023‐364 and 2024‐034, the Juno spacecraft made close passages of Jupiter's moon Io, at altitudes of about 1,500 km. Data obtained from the first flyby, when the spacecraft was on magnetic field lines connected to both Jupiter and Io, revealed deep flux decreases. In addition, Juno's energetic particle detectors observed tens to hundreds of keV electron and proton beams. Such beams could be generated near Jupiter on field lines associated with Io. The second encounter occurred in the plasma wake and a more modest flux decrease was observed. Furthermore, data from both encounters suggest a spatially extensive decrease in >1 MeV electrons that includes regions inward of Io's orbit. In the immediate vicinity of Io, signatures of absorption likely dominate the data whereas diffusion and wave‐particle interactions are expected to be needed to understand MeV electron data in the wider spatial region around Io. Plain Language Summary: Jupiter's magnetospheric plasma overtakes Io in its orbit. This causes a cavity to be formed over the hemisphere of Io that leads its orbital motion. Within this cavity subtle details of the plasma and energetic charged particle environment can be extracted from the signal, usually dominated by radiation at these distances. Examples include beams traveling in the direction from Jupiter to the moon, with little evidence of reflection at Io. Another major finding of this work is that there is a large region both along Io's orbit and even radially inward of it with a lower level of MeV electron flux. Guided by previous modeling, the most likely candidates for shaping the data are absorption by the moon, wave‐particle interactions that can scatter particles into Jupiter's atmosphere, and diffusion. Key Points: Deep flux decreases over Io and in its immediate wake caused by losses to the moon's surface were observed in Juno JEDI dataJuno JEDI detected narrow field‐aligned beams of electrons and protons directed toward Io's north poleMoon absorption and wave‐particle interactions may explain the loss of >1 MeV electrons that extend both inward and outward of Io's orbit [ABSTRACT FROM AUTHOR]

Jupiter's moon Europa contains a subsurface ocean whose presence is inferred from magnetic field measurements, the interpretation of which depends on knowledge of Europa's local plasma environment. A recent Juno spacecraft flyby returned new observations of plasma electrons with unprecedented resolution. Specifically, powerful magnetic field‐aligned electron beams were discovered near Europa. These beams, with energies from ∼30 to ∼300 eV, locally enhance electron‐impact‐excited emissions and ionization in Europa's atmosphere by more than a factor three over the local space environment, and are associated with large jumps of the magnetic fields. The beams therefore play an essential role in shaping Europa's plasma and magnetic field environment and thus need to be accounted for electromagnetic sounding of Europa's ocean and plume detection by future missions such as JUICE and Europa Clipper. Plain Language Summary: A recent Juno spacecraft close flyby of Jupiter's moon Europa revealed the presence of powerful electrons beams. Based on previous observations and modeling of electron beams at the moon Io, such beams were not expected to be observed so close to Europa. Overall, the proximity of the beams to Europa indicates that the acceleration of these electrons takes place much closer to Europa than anticipated and that these beams, therefore, stem from a new and previously unknown acceleration mechanism. The beams are predicted to have an outsized influence on the ionization of the constituents of Europa's tenuous atmosphere and are accompanied with large magnetic field perturbations. Hence, these electron beams are an important ionization source that modify the moon's ionosphere, the electric current systems, and the magnetic field environment. In particular, the presence of electron beams will affect plasma conditions that are used to infer the extent of a subsurface ocean via the magnetic induction signal. These beams significantly impact the space plasma environment around Europa which needs to be accounted for by future missions such as ESA's (European Space Agency) JUICE (Jupiter Icy Moons Explorer) and NASA's (National Aeronautics and Space Administration) Europa Clipper mission. Key Points: Powerful electron beams that significantly shape Europa's space environment are discovered during a Juno flybyThe beams enhance electron‐impact‐excited emissions in Europa's atmosphere and are associated with large jumps of the magnetic fieldsThe beams' proximity to Europa and their pitch angle distribution constrain the source acceleration to be near or within the plasma disk [ABSTRACT FROM AUTHOR]

Energetic particle injections are commonly observed in Jupiter's magnetosphere and have important impacts on the radiation belts. We evaluate the roles of electron injections in the dynamics of whistler‐mode waves and relativistic electrons using Juno measurements and wave‐particle interaction modeling. The Juno spacecraft observed injected electron flux bursts at energies up to 300 keV at M shell ∼11 near the magnetic equator during perijove‐31. The electron injections are related to chorus wave bursts at 0.05–0.5 fce frequencies, where fce is the electron gyrofrequency. The electron pitch angle distributions are anisotropic, peaking near 90° pitch angle, and the fluxes are high during injections. We calculate the whistler‐mode wave growth rates using the observed electron distributions and linear theory. The frequency spectrum of the wave growth rate is consistent with that of the observed chorus magnetic intensity, suggesting that the observed electron injections provide free energy to generate whistler‐mode chorus waves. We further use quasilinear theory to model the impacts of chorus waves on 0.1–10 MeV electrons. Our modeling shows that the chorus waves could cause the pitch angle scattering loss of electrons at <1 MeV energies and accelerate relativistic electrons at multiple MeV energies in Jupiter's outer radiation belt. The electron injections also provide an important seed population at several hundred keV energies to support the acceleration to higher energies. Our wave‐particle interaction modeling demonstrates the energy flow from the electron injections to the relativistic electron population through the medium of whistler‐mode waves in Jupiter's outer radiation belt. Key Points: Chorus wave generation due to electron injections is demonstrated by their correlative occurrence and wave instability analysisWhistler‐mode waves scatter electrons into the loss cone and cause diffuse auroral precipitation with intensities of 60–160 erg/cm2/sChorus waves cause local acceleration of MeV electrons in several days, further aided by the seed electron population from injections [ABSTRACT FROM AUTHOR]

The micro Advanced Stellar Compass is an attitude reference for the MAG investigation onboard Juno. The μASC camera head unit images the star field with a CCD that is also sensitive to particles with enough energy to pass through the camera shielding: >15 MeV electrons and >80 MeV protons. This provides the capability to monitor fluxes of high‐energy particles in Jupiter's magnetosphere. A survey of energetic electron fluxes sampled during the first 47 Juno orbits reveals instances of variations observed when Juno is traversing the M‐shell of the Galilean moons. Juno's traversal of the Europa M‐shell often results in distinctly particle signatures. We present the μASC observations of increased electron flux during the crossing of Europa's plasma wake, and depletion of energetic electron flux on the upstream side. The upstream/downstream differences indicate that the wake environment of Europa drives strong pitch angle scattering on relativistic electrons. Plain Language Summary: The attitude reference (μASC) used for the MAG investigation onboard Juno is also sensitive to particles with enough energy to pass through the camera shielding. This provides the capability to monitor fluxes of high‐energy particles in Jupiter's magnetosphere, as the Juno has done since orbit insertion. A μASC survey of electron fluxes reveals instances of variations observed when Juno is traversing the M‐shell of Jupiter's moon Europa. We present particle signatures related to the interaction with Europa and discuss the implications. Key Points: Europa's wake affects the high‐energy electron driftshell by scattering electrons into the loss‐coneIncrease in e− flux is around x2.3 at distances ∼30 RE, and is gradually dissolved as far as 20° downstreamEuropa will stop the energetic electron drift shells and will be mostly free from hard radiation on the leading side [ABSTRACT FROM AUTHOR]

In this study, we examine particle energization and injections that show energetic electron enhancements at both MMS in the magnetotail and Van Allen Probes in the inner magnetosphere. Observing injections along with a corresponding flow burst allows us to better understand injections overall. Searching for suitable events, we found that only a small number of events at MMS had corresponding injections that penetrated far enough into the inner magnetosphere to observe with Van Allen Probes. With the four suitable events we did find, we compared the energy spectra at the two spacecraft and mapped the boundary of where the injection entered the inner magnetosphere. We found that, among these injections in the inner magnetosphere, the electron flux did not increase above ~400 keV, similar to previous results, but the corresponding signatures in the tail observed increased fluxes at 600 keV or higher. There does not appear to be a comparable flux increase at Van Allen Probes and MMS for a given event. None of our injections included ion enhancements at Van Allen Probes, but one included an ion injection at geosynchronous orbit in the GOES spacecraft. All of our injections were dispersed at Van Allen Probes, and we were therefore able to map an estimate of the injection boundary. All of the injections occurred in the premidnight sector. Although we found some events where particle energizations in the tail are accompanied by inner magnetospheric injections, we do not find a statistical link between the two. [ABSTRACT FROM AUTHOR]

Optical remote sensing observations have suggested that the top layer of Europa's icy surface is heavily affected by external weathering agents. To model and understand these effects, it is necessary to characterize the environment as fully as possible. In this paper, we focus on one agent in the environment (energetic electrons). We show Juno electron data from its 2022 Europa flyby and other time periods. While the Juno sensor used here (Jupiter Energetic Particle Detector Instrument) was not designed to obtain high quality electron data in an intense radiation environment, it is possible to extract information such as how Europa blocks energetic particles from accessing some of the surrounding space. The decrease in charged particle flux in Europa's wake provides an upper limit on the precipitation fluxes of the same particles. We also report that electron pitch angle distributions near Europa for the single energy channel considered here are time variable and not isotropic. Plain Language Summary: We present energetic electron data obtained when the Juno spacecraft crossed the plasma wake of the moon Europa in 2022. A major goal of this work is to estimate the amount of blockage of MeV electrons near the moon to inform radiation estimates for future Europa orbiters and landers. While the Jupiter Energetic Particle Detector Instrument does not directly detect particles between 1 and 20 MeV, using knowledge gained since the instrument began obtaining data we were able to estimate that about 80% of the particles in question are blocked by Europa in its wake at low altitude. Research on the weathering of Europa's surface by electrons is also discussed. Key Points: Jupiter Energetic Particle Detector Instrument electron data relevant to Europa are presentedWe estimate Europa's blockage causes an ∼80% reduction of ∼1–20 MeV electrons in the immediate plasma wakePitch angle distributions are computed from 70 keV electron data and show time variability [ABSTRACT FROM AUTHOR]

Author(s): B. H. Mauk (corresponding author) [1]; D. K. Haggerty [1]; C. Paranicas [1]; G. Clark [1]; P. Kollmann [1]; A. M. Rymer [1]; S. J. Bolton [2]; S. M. [...]