This session addresses how Juno’s discoveries advance our knowledge of auroral acceleration and wave–particle interactions, auroral phenomenology, magnetosphere–ionosphere coupling, moon–magnetosphere interaction, magnetopause structure, and plasma transport across the Jovian magnetosphere. These results provide key constraints to prepare for the next phase of Jovian exploration with ESA’s JUICE mission and NASA’s Europa Clipper. We welcome contributions highlighting Juno results, along with insights from past and future missions, to better understand Jupiter’s magnetosphere.
Orals: Fri, 8 May, 08:30–10:10 | Room L3
Observations from Juno have indicated that Jupiter’s polar cap is a unique plasma environment, with plasma density as low as 10−3 cm−3, precipitating heavy ions at megavolt energies, broadband upgoing energetic electrons and strong wave emissions. Low plasma densities suggest that the ionospheric plasma in this region is held down by ambipolar potentials due to the large gravitational potentials that limit the ability of thermal plasma to escape the ionosphere. Despite this barrier, Juno observes upward, energetic electron beams, requiring a low-altitude acceleration of these electrons. The low plasma density favors the formation of parallel electric fields that could accelerate these electrons, even in the presence of weak downward field-aligned currents associated with co-rotation. However, observations of precipitating heavy ions (Oxygen, Sulfur) suggest that these field lines are closed in the Jovian plasma sheet. These ions may be scattered into the loss cone by electromagnetic cyclotron waves that propagate as kinetic Alfvén waves toward the ionosphere, enhancing the field-aligned current. These processes will be investigated using a combination of fluid and kinetic modeling of polar field lines at Jupiter.
How to cite: Lysak, R., Sulaiman, A., Elliott, S., and Eshetu, W.: Particle acceleration in Jupiter’s polar region, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4091, https://doi.org/10.5194/egusphere-egu26-4091, 2026.
Whistler-mode waves are a wave mode in plasma occurring near and below the electron cyclotron frequency. They are commonly observed in planetary magnetospheres and play a crucial role in accelerating and precipitating magnetospheric electrons. Using Juno’s observations, we investigate these waves in Jupiter’s magnetosphere, focusing on the region between 20 and 80 Jupiter radii on the post-midnight-to-dawn side. Observations from the Waves instrument show that these waves primarily occur in the lobes, where the magnetic field is strong and plasma density is low, rather than in the central magnetodisk, where the field is weaker and plasma is denser. Simultaneous electron measurements from JADE-E, combined with dispersion relation analysis, indicate that these waves are likely driven by a mono-directional electron population between ∼0.1 and 10 keV propagating anti-Jupiter-ward. Further controlled studies show that a local flux minimum at ∼0.3 keV in the electron energy spectrum, commonly observed during whistler-mode waves, is critical for wave growth. Based on their direction of motion, we suggest that these mono-directional electrons and the whistler-mode waves they generate are related to magnetosphere-ionosphere coupling. Our findings offer new insights into the interplay between whistler-mode waves and electrons in Jupiter’s magnetosphere.
How to cite: Liu, Z.-Y., Andre, N., Blanc, M., Li, L., Rabia, J., Allegrini, F., Ebert, R. W., Kurth, W. S., Connerney, J. E. P., and Bolton, S. J.: Whistler-Mode Waves and Associated Electron Distributions in Jupiter’s Middle and Outer Magnetosphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9596, https://doi.org/10.5194/egusphere-egu26-9596, 2026.
Jupiter's ionosphere provides the electrodynamic boundary for magnetosphere–ionosphere (M-I) coupling, shaping how field-aligned currents close, how momentum is exchanged through ion-neutral drag, and how magnetospheric energy input is distributed in the upper atmosphere. Despite its central role, the vertical structure and variability of Jupiter’s electron density remain incompletely characterized, particularly at high latitudes associated with auroral processes.
We present an overview of electron density profiles derived from the full set of Juno radio occultations processed to date, complemented by neutral atmospheric profiles retrieved along the same limb geometries. This dataset enables a systematic assessment of how key ionospheric characteristics - peak electron density, peak altitude, and vertically integrated content - vary with local time, latitude, and illumination. By examining ionospheric structure in the context of the co-retrieved neutral atmosphere, we investigate how variations in scale height and background state may shape conductivity profiles relevant to current closure and the efficiency of M-I coupling.
We place particular emphasis on occultations sampling auroral and high-latitude regions, where changes in electron density are expected to modulate the coupling between magnetospheric forcing and thermospheric response. Overall, these profiles provide an observational basis for ionosphere-thermosphere modeling and for the conductivity and boundary assumptions commonly used in M-I coupling studies.
How to cite: Galanti, E., Smirnova, M., Caruso, A., Buccino, D., Bolton, S., Fonsetti, M., Gomez Casajus, L., Hubbard, W., Parisi, M., Park, R., Steffes, P., Tortora, P., Zannoni, M., and Kaspi, Y.: A Juno radio-occultation view of Jupiter's ionosphere with implications for magnetosphere-ionosphere coupling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9313, https://doi.org/10.5194/egusphere-egu26-9313, 2026.
Auroral acceleration by inertial Alfvén waves is commonly invoked to explain the preponderance of broadband electron energy distributions observed above Jupiter’s main auroral zones. These distributions extend to 100s keV and MeV energies and are associated with the brightest auroras. Jupiter’s low-altitude auroral zones represent a highly-magnetized, density-depleted plasma regime that is conducive to inertial Alfvén wave acceleration. However, despite the robust theoretical foundation, observational evidence remains lacking. Here, we perform a detailed analysis of auroral electron distributions above Jupiter’s auroral zones. We demonstrate the two types of distributions – monoenergetic and broadband – are separated by length scales where the perpendicular wave number is respectively less than or comparable to the inverse of the electron inertial length. Furthermore, in contrast to the longstanding acceptance that Alfvén waves exclusively originate remotely from Jupiter’s equatorial plasma sheet, we demonstrate they can be locally generated at Jupiter’s low altitudes via a beam-plasma instability. From this new understanding, we find locally-generated Alfvén waves are directly responsible for accelerating the most intense auroral electrons at Jupiter.
How to cite: Sulaiman, A., Mauk, B., Lysak, R., Kruegler, N., Sarkango, Y., Szalay, J., Bolton, S., Clark, G., Damiano, P., Eshetu, W., Elliott, S., Kurth, W., and Skinner, E.: Locally generated low-altitude Alfvén waves deliver Jupiter’s brightest auroras, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-23210, https://doi.org/10.5194/egusphere-egu26-23210, 2026.
During Juno’s extended mission, the spacecraft’s periapsis migrated toward Jupiter’s north pole, enabling high-resolution observations of auroral regions. At microwave wavelengths, these auroral features appear as localized reductions in brightness temperature (“cold spots”). Here we present observations from Juno Perijoves 56–72 using the Microwave Radiometer (MWR). MWR measures thermal emission from Jupiter’s deep atmosphere, which is partially absorbed by ionization produced by precipitating energetic electrons in the ionosphere. By exploiting MWR’s multi-frequency observations, we use the frequency dependence of electron–neutral collisional absorption to probe the vertical extent of auroral ionization at depths well below those accessible to ultraviolet measurements.
We find systematic differences among auroral regions. The deepest ionization occurs at the Io footprint, is moderate along the main auroral oval, and is shallowest in the polar cap. Modeling of the multi-frequency absorption indicates that the Io footprint requires a substantial population of precipitating electrons with energies in the tens-of-MeV range, whereas the main oval can be explained without invoking such high-energy electrons. These results place new constraints on the energy and depth of electron precipitation in Jupiter’s aurora and demonstrate the unique capability of MWR multi-frequency measurements to diagnose deep ionospheric structure, complementing ultraviolet, infrared, and radio occultation observations.
How to cite: Zhang, Z., Waite, J., Bhattacharya, A., Levin, S., Steffes, P., Adumitroaie, V., and Oyafuso, F.: Deep Auroral Ionization and High-Energy Electron Precipitation in Jupiter’s North Polar Region from Juno MWR, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13325, https://doi.org/10.5194/egusphere-egu26-13325, 2026.
The Juno spacecraft continues to map the gas giant’s complex magnetic field and particle environment, taking advantage of the natural evolution of Juno’s polar orbit. Juno’s first orbits had perijoves just northward of the equator. With each subsequent orbit, Juno’s perijove marches northward by ∼1°, owing to the apsidal precession of the orbit caused by Jupiter’s tidal bulge. As Juno’s periJove migrated further northward in EM1 (through orbit 76) and EM2, the spacecraft began sampling (via particle counts in the MAG investigation camera head units, or CHUs) a population of very energetic (>20 Mev) particles with pitch angles greater than 50 degrees both inbound and outbound from perijove at a particular M-shell defined by an equatorial magnetic field minimum ~ 0.35 Gauss. It is the most challenging radiation environment encountered thus far by the Juno spacecraft, with implications for spacecraft and instrument operations as well as magnetospheric dynamics and electromagnetic radiation. This population crosses the Jovigraphic equator at radii between 2.15 and 2.39 Rj, a region of space occupied by the Thebe Gossamer ring (~1.8 – 3.1 Rj), motivating speculation regarding pitch angle scattering of inward diffusing particles by electrically charged dust.
How to cite: Connerney, J., Timmins, S., Jorgensen, J., Bolton, S., and Levin, S.: Juno Measurements of Jupiter’s Magnetic Field and Innermost Radiation Belts, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14115, https://doi.org/10.5194/egusphere-egu26-14115, 2026.
Characterizing the relationship between the solar wind and Jupiter’s magnetosphere is crucial for understanding its role in the variability of the bow shock and magnetospheric standoff distances and boundaries. Although the magnetosphere is predominantly supported by internal plasma pressure, the solar wind nevertheless plays a significant role in the shape, location, and size of the overall magnetosphere structure. Since Juno arrived at Jupiter in June of 2016, it has completed over 1600 crossings through the magnetopause and bow shock, which have been identified by examining particle and wave measurements from the Juno instruments. We compare these crossings with data from previous missions (e.g., Pioneer, Voyager, and Galileo) to compile an extensive database of crossings, allowing for thorough investigation of the magnetopause and bow shock boundaries. Previous models of the Jovian system do not account for extremely high solar wind dynamic pressures that cause strong compressions of the magnetosphere, such as the event observed in October of 2024, when the magnetopause boundary—usually located between 60-100 Rj upstream of Jupiter—was found as close as 35 Rj. We derive scaling factors of these models at various solar wind dynamic pressures, such as the Joy et al. 2002 model, in order to explore a correlation between such compressed standoff distances and the solar wind.
How to cite: Fuller, G., Bagenal, F., wilson, R., Allegrini, F., Collier, M., Ebert, R., Hospodarsky, G., Kurth, W., and Louis, C.: Survey of Bow Shock and Magnetopause Boundaries Observed by Juno, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22853, https://doi.org/10.5194/egusphere-egu26-22853, 2026.
Discrete energy bands of ion fluxes, typically organized in velocity with equal separations, have been frequently observed in Jupiter’s magnetosphere either in association with Galilean moons or in regions far from their influence. Here, we focus on the latter and propose that these bands are manifestations of bounce-phase structuring, analogous to drift-phase structuring responsible for the well-known zebra-stripe patterns. In our proposed framework, latitude-dependent electric-field perturbations interact with ions at different bounce phases, producing phase-dependent energy modulations. As the ions continue to bounce at their respective bounce frequencies, which scale with ion velocity, these modulations naturally evolve into discrete, velocity-ordered banded structures. We examine several potential sources of latitude-dependent electric fields, including impulsive disturbances and wave-related processes. Test-particle simulations reproduce the key observational features. These results support bounce-phase structuring as a unifying interpretation of both non-moon and moon-associated discrete bands, and provide a new diagnostic perspective on Jovian magnetospheric dynamics.
How to cite: wu, Y.-Z., Zhou, X.-Z., and Zong, Q.-G.: Discrete Energy Bands Beyond Galilean Moons: Bounce-Phase Structuring of Jovian Magnetospheric Particles, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4492, https://doi.org/10.5194/egusphere-egu26-4492, 2026.
Dust dynamics in Jupiter’s inner ring system are effectively shaped by electromagnetic forces arising from the planet’s rapid rotation and intense magnetic field. Previous studies of Jupiter’s rings have relied primarily on optical imaging, which provides initial constraints on the three-dimensional dust distribution and in-situ dynamical processes. The Juno mission offers a unique opportunity to probe the Jovian ring system, as the Waves instrument enables in-situ detection of dust impacts within Jupiter’s innermost magnetosphere.
In this study, we focus on dust impact detections from Juno Waves burst-mode electric field measurements. A convolutional neural network (CNN) is applied to identify dust impact signals and distinguish them from plasma waves and instrumental noise, allowing us to derive dust impact rates and infer dust number densities along the Juno trajectory. These measurements provide new observational constraints on the spatial distribution of dust in Jupiter’s inner ring system.
The inferred dust impact rates and number densities are broadly consistent with previous optical observations of Jupiter’s ring system and with earlier Juno-based dust detections reported by Ye et al. (2020). We find that dust impacts are strongly concentrated near the equatorial plane, with peak impact rates reaching ~8 s⁻¹ and maximum dust number densities of ~3 × 10⁻⁶ m⁻³. These results support the picture of a dense, equatorially confined dust population associated with Jupiter’s inner rings.
In addition to these previously reported features, the Juno observations reveal new characteristics of the dust distribution. In particular, we observe a pronounced north–south asymmetry in the inferred dust number density, as well as a localized density enhancement near ~1.1 RJ along the spacecraft trajectory during a limited number of Juno orbits. Due to the monotonic evolution of the location of the Juno equatorial crossing in the local-time radial distance space, whether this density enhancement represents a transient ring or a spatially confined ring arc remains to be elucidated.
How to cite: Zhang, W., Cao, H., Ma, D., Kurth, W. S., Wilkinson, D., Shen, M., Hospodarsky, G., and Bolton, S.: Machine-learning-based detection of dust impacts with Juno Waves: Evidence for a new (transient) dusty ring? , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15616, https://doi.org/10.5194/egusphere-egu26-15616, 2026.
Since 2016, the Juno spacecraft has been orbiting Jupiter. Recently unique insights in the regions within Io’s orbit has been accessible by the evolution of Juno's orbit. The Advanced Star Compass (ASC) primarily serves to determine the orientation of the magnetometer. However, the ASC detector is also sensitive to high-energy particles, enabling it to measure the Jovian radiation environment. Specifically, the ASC can detect electrons with energies greater than 15 MeV and protons with energies exceeding 120 MeV.
Juno has performed 80 orbits since its arrival at Jupiter system, traverses longitudinal regions of the Jovian system and it scans effectively the entire Jovian radiation belts with its orbit evolution drift of the line of apsides south. The ASC has consistently recorded variations in radiation levels when Juno crosses magnetic field regions. In the region within the Io orbit, the shape of the radiation belts is confirmed where particles are trapped in the magnetic field and they bounce between the mirror points. Closer to the planet particles are lost due to the extremely inhomogeneity structure of the Jovian magnetic field in these regions, where there is not a minimum of the magnetic field and thus a particle consequently are lost when reaching the planet’ atmosphere. This extremely dynamic region offers insight into both charged particle transport and energization of these, hitherto unexplored.
We present the observations and a possible transport mechanism for these particles in this region, which will allow us to estimate the particle flux and their energy levels
How to cite: Merayo, J., Jørgensen, J., Denver, T., Benn, M., Jørgensen, P. S., Connerney, J., and Bolton, S.: Observation of high energy particles in Jupiter’s magnethospere within the Io region, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19922, https://doi.org/10.5194/egusphere-egu26-19922, 2026.
Based on a kinetic model, we reveal the important role of modified electron acoustic waves (MEAWs) in auroral electron acceleration. In the transition region between the magnetosphere and ionosphere, parallel electric fields are generated through mode coupling between kinetic Alfvén waves (KAWs) and MEAWs. These fields are subsequently sustained by continuous energy input from Alfvén waves originating in the magnetosphere, along with the thermal pressure of hot electrons that replace colder populations. Under the incidence of long-period Alfvén waves carrying upward field-aligned currents, a parallel potential drop forms in the transition region, leading to quasi-static electron acceleration. This mechanism provides a plausible link between shear Alfvén waves and quasi-static auroral electron acceleration. Our results further demonstrate that the lower boundary of the auroral acceleration region (AAR) descends as the potential drop increases, the hot electron density rises, or the hot electron temperature decreases. Moreover, the altitude of the AAR is modulated by ionospheric plasma density and temperature, which define the structure of the transition region. Specifically, lower ionospheric plasma temperature and density lead to a decrease in the lower boundary of the AAR. These findings contribute to explaining the formation of aurorae on Jupiter.
How to cite: Shi, R.: Altitude Dependence of Quasi-Static Parallel Electric Field Generation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2470, https://doi.org/10.5194/egusphere-egu26-2470, 2026.
Jupiter’s radiation belts are the most energetic, intense and ion-rich in the entire solar system. To constrain source, acceleration, and loss mechanisms, across an ion mass and energy range not typically accessible in other planetary magnetospheres, the composition and distribution of heavy ions within the Jovian magnetosphere should be first resolved. Relatively little is known about their global distribution and dynamics in the jovian magnetosphere, particularly above several MeV/nucleon or for species different than sulfur or oxygen. In this work, we survey the full Heavy Ion Counter (HIC) dataset from the Galileo mission in order to characterize the composition of Jupiter’s >5 MeV/nucleon ions (Z>6), with an extra focus on minor species. We unambiguously resolve 10 different ion species, and provide estimates of their energy and distance dependent relative abundances. At least five new species are resolved (N, Ne, Si, K and possibly Ca and Fe), each likely mapping to different magnetospheric and/or weathering processes. A key finding is that abundances of species like Carbon, Neon and Silicon are reminiscent of those in solar energetic particles comparable to magnetospheric sulfur, indicating a considerable solar input into Jupiter’s heavy ion radiation belts. The same may apply for more abundant species like oxygen: its trapping region extends out to Ganymede’s distance, which would only be possible if oxygen is multiply charged, as it is the case for oxygen in solar energetic particle population.
How to cite: Plainaki, C., Roussos, E., Krupp, N., Grassi, D., Kollmann, P., Mura, A., and Grimani, C.: Investigating the composition of Jupiter’s energetic heavy ion environment, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11080, https://doi.org/10.5194/egusphere-egu26-11080, 2026.
Jupiter’s polar stratosphere exhibits unique chemical and dynamical processes that shape its atmospheric composition and structure. Hydrocarbon observations from multiple instruments (e.g., Voyager/IRIS, Cassini/CIRS, IRTF/TEXES, Juno/UVS, and JWST/MIRI) reveal abundance enhancements and strong latitudinal variations of C2 hydrocarbon species within the auroral regions. These enhancements are attributed to the influence of auroral energy deposition and possibly enhanced vertical mixing. IRTF/TEXES and JWST/MIRI observations also provide new constraints on the vertical structure of the polar atmosphere, suggesting that the methane homopause is located at higher altitudes in auroral regions than at lower latitudes. In addition, some observations indicate that Jupiter’s previously known aerosol layer is situated at higher altitudes in the polar regions (above about 20 mbar) compared to lower latitudes (around about 50 mbar). Magnetosphere–ionosphere–thermosphere coupling in Jupiter’s polar regions generates ionospheric winds with velocities of several km/s, which may propagate downward to the 0.1 mbar level, where neutral winds appear to be co-located with those measured at higher altitudes. Jupiter’s polar atmosphere thus constitutes a highly complex system in which magnetospheric forcing is strongly coupled with chemistry and dynamics from the ionosphere down to the tropopause. Understanding the distribution of hydrocarbons at high latitudes, and the extent to which they control the atmospheric radiative balance, is crucial for constraining upper-atmospheric dynamics. In this contribution, we provide a general overview of the physical and chemical processes governing Jupiter’s polar regions and present preliminary results from the JAFAR project, designed to investigate Jupiter’s polar atmosphere and the fate of aerosols, in preparation for the JUICE arrival in 2031.
How to cite: Hue, V., Cavalié, T., Couturier-Tamburelli, I., Fouchet, T., Gautier, T., Moreno, R., Noble, J. A., Sinclair, J. A., Benne, B., Benmahi, B., Guerlet, S., and Rodríguez-Ovalle, P.: Understanding Jupiter’s polar Atmosphere & the Fate of the AeRosols (JAFAR), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14661, https://doi.org/10.5194/egusphere-egu26-14661, 2026.
The Jovian InfraRed Auroral Mapper (JIRAM) aboard NASA’s Juno spacecraft has significantly advanced our understanding of Jupiter’s aurorae by providing infrared observations with unprecedented spatial resolution. These measurements reveal fine-scale structures associated with H3+ emissions and enhanced CH4 concentrations over the polar caps, offering new insights into the coupling between Jupiter’s magnetosphere, thermosphere, and ionosphere. Leveraging Juno’s elliptical polar trajectory, the JIRAM imager and spectrometer have conducted repeated close-range observations of Jupiter’s auroral regions throughout the mission. This unique vantage point enables investigation of the morphology and temporal evolution of H3+ and CH4 emissions, particularly in the less-studied southern hemisphere, which remains largely inaccessible to Earth-based instruments. Extending beyond earlier analyses of Juno’s first perijove (PJ), we examine JIRAM observations from PJ1 (27 August 2016) to PJ40 (25 February 2022), restricting our study to orbits that provide the most complete spectroscopic coverage of the auroral regions, thereby enabling large-scale quantitative analysis and inter-orbit comparison. We derive the temperature and column density of H3+ in Jupiter's auroral regions in the 3.2–3.8 mm range to generate detailed distribution maps. These reveal significant variability in auroral emissions, including a longitudinal displacement of the southern aurora over time, also evident in JIRAM L-band (3.3–3.6 mm) imagery. We further find that 3.3-mm methane bright spots are primarily confined within the auroral oval, with occasional indications of emission extending beyond the main boundary. Together, these results highlight the dynamic nature of Jupiter’s infrared aurora, consistent with variable atmospheric response to time-varying magnetospheric forcing.
Acknowledgments:
The authors acknowledge the Agenzia Spaziale Italiana (ASI) for supporting of the JIRAM contribution to the Juno mission, including this work, under the ASI contract 2016-23-H.0.
How to cite: Castagnoli, C., Dinelli, B. M., Altieri, F., Migliorini, A., Mura, A., Sordini, R., Tosi, F., Noschese, R., Adriani, A., Cicchetti, A., Grassi, D., Moirano, A., Piccioni, G., Plainaki, C., and Sindoni, G.: Survey of H3+ and CH4 Emissions in Jupiter's Aurorae from Juno/JIRAM Observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9755, https://doi.org/10.5194/egusphere-egu26-9755, 2026.
Io and its torus, the “Io System” for short, play a key role in the global dynamics of the Jupiter System. While Io’s interior is heated by tides, its extended gas and plasma tori, driven by Io’s volcanic activity, feed mass, momentum and energy into the magnetosphere and its fast-spinning magnetodisk. The complex interplay between these different elements results in a highly dynamic system, whose variability spans a broad range of timescales, from hours to decades and more, and remains poorly understood. Despite the current limitations in our knowledge of the Io system, progress in understanding its variability will directly translate into a better understanding of the mechanisms driving this variability, and as a direct consequence, into a much better grasp of the drivers and variabilities of the Jupiter System as an integrated whole.
How to cite: Blanc, M. and Bolton, S.: Exploring the variability of Io and its torus via observations and modelling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-23218, https://doi.org/10.5194/egusphere-egu26-23218, 2026.
Posters virtual: Mon, 4 May, 14:00–18:00 | vPoster spot 4
EGU26-14914 | Posters virtual | VPS27
The Juno PJ57 and PJ58 flybys of Io: Multi-species physical chemistry simulationsMon, 04 May, 14:24–14:27 (CEST) vPoster spot 4
The Juno spacecraft made close flybys of Io on Dec. 2023 (PJ57) and Feb 2024 (PJ58) above respectively the northern/southern hemisphere with an altitude at closest approach (CA) of ~1,500 km.
On PJ57, Juno went through the Alfven wing and both the Juno/Waves and Radio-occultation measurements showed a surprising large electron density nel ~ 28,000 near closest approach. On PJ58, Juno flew slightly behind the Alfven wing and the instruments measured a plasma density consistent with the background plasma torus density.
We run numerical simulations of the plasma/atmosphere interaction along teh PJ57 and PJ58 flyby to constrain IO’s polar atmosphere. Our numerical simulations are based on (1) A prescribed atmospheric composition and distribution of S, O, SO2 and SO; (2) A MHD code to calculate the plasma flow into Io’s atmosphere; (3) A multi-species physical chemistry code to compute the change of the plasma properties (ion densities, composition and temperature) during the plasma/atmosphere interaction (4) a formulation of the ionization by the field-aligned electron beams used for auroral electrons on Earth.
We compute the multi-charged ion composition of the plasma along each flyby and compare to the Juno/JADE measurements to infer the atmosphere composition (O, S, SO2, SO) and density at polar latitudes.
How to cite: Dols, V. and Bagenal, F.: The Juno PJ57 and PJ58 flybys of Io: Multi-species physical chemistry simulations , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14914, https://doi.org/10.5194/egusphere-egu26-14914, 2026.
EGU26-14123 | Posters virtual | VPS27
Detection of negative carbon and oxygen pickup ions from dust orbiting JupiterMon, 04 May, 14:27–14:30 (CEST) vPoster spot 4
We report on observations of negative carbon and oxygen pickup ions (PUIs) originating from dust orbiting Jupiter. The PUIs are observed at altitudes of a few thousand kilometers (~4,800 – 10,200 km) above the 1-bar level of Jupiter’s atmosphere and up to ~11,000 – 15,000 km from the equatorial plane, thus providing constraints on the location of the dust population and its composition. The Jovian Auroral Distributions Experiment – Electron sensors on Juno detect these PUIs because of the combination of a fast-moving spacecraft and the large Keplerian orbital speed of the dust near Jupiter. We demonstrate that this scenario is consistent with the observations. We find a PUI C/O ratio of 10 ± 5 and a PUI energy release of ~11 ± 9 eV. Electron stimulated desorption is a likely process forcreating these PUIs. The dust is well inside the halo population and likely carbonaceous.
How to cite: Allegrini, F., Szalay, J., McComas, D., Ebert, R., Bolton, S., Clark, G., Connerney, J., Kurth, W., Louarn, P., Mauk, B., Pontoni, A., Saur, J., Valek, P., Wang, J.-Z., and Wilson, R.: Detection of negative carbon and oxygen pickup ions from dust orbiting Jupiter, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14123, https://doi.org/10.5194/egusphere-egu26-14123, 2026.
EGU26-4537 | Posters virtual | VPS27
Temporal Variations of Jupiter’s Plasma Disk Observed by JunoMon, 04 May, 14:30–14:33 (CEST) vPoster spot 4
Jupiter’s magnetosphere features internal mass loading from its innermost moon Io. The neutral gases from Io’s escaping atmosphere are ionized to become the plasma torus, which mainly consists of sulfur and oxygen ions. Under centrifugal force, plasma in the torus is transported outward and forms a thin plasma disk near the equator, while the transport mechanism and timescale remain unclear. Since 2016, the plasma disk between 10 and 50 RJ has been continuously observed by the Juno mission. Using multi-year thermal plasma measurements from the JADE ion detector, we perform an analysis that reveals significant temporal variation of plasma disk from a long-term perspective. For different Juno orbits, the plasma disk observations are categorized as either enhanced or depleted based on plasma density. Extreme cases indicate vastly different states of the plasma disk, with variations exceeding one order of magnitude. Further analysis of multiple plasma disk crossings by Juno reveals correlations between density enhancements and fluctuations in plasma density and magnetic field profiles, which are typical features of flux tube interchange. This suggests that flux tube interchange is triggered by an increase in the plasma source and is considered the primary mechanism for outward plasma transport. Finally, Juno’s in-situ measurements also show a correlation with remotely sensed Io’s torus ribbon brightness from the ground-based IoIO observatory, lagged by about 30 to 50 days. This suggests that the temporal variation of the plasma disk is modulated by changes in Io’s torus and that the average plasma transport time from the torus to the plasma disk is around 40 days.
How to cite: Bagenal, F. and Wang, J.-Z.: Temporal Variations of Jupiter’s Plasma Disk Observed by Juno , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4537, https://doi.org/10.5194/egusphere-egu26-4537, 2026.
