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.

How to cite: Devinat, M., André, N., and Blanc, M.: A self-consistent model of radial transport in the magnetodisks of gas giants including interhemispheric asymmetries, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8604, https://doi.org/10.5194/egusphere-egu24-8604, 2024.

The current Juno and recent Cassini missions have yielded unprecedented accuracy and resolution of the gravity fields of Jupiter and Saturn. The new observations of zonal harmonics through J12 have led to a new generation of interior models. Previously, interior models of two or three adiabatic layers were sufficient to satisfy gravity observations. However, to satisfy the Cassini and Juno observations, interior models require more complexity, with recent works proposing five layers, and the presence of gradients in composition and entropy. I describe the hydrostatic equations relevant to a rotating fluid planet with variable density, composition and entropy. Composition is formulated with a simple version of the additive volume law. Stability is described in terms of gradients in specific entropy and composition (mass fraction), which is assumed to be static (or slowly varying) . Relations between composition, entropy and diffusion parameters variation are described in terms of the density ratio, which is a prominent parameter of semiconvection (double diffusive convection). The resulting set of thermodynamic equations, along with gravity, are solved iteratively, calibrated by, and compared to the recent ab-initio EOS results of French et al. (2012) and Militzer et al. (2022).  To further simplify the thermodynamic formulation, non-adiabatic interior models that are polytropic where they are adiabatic are explored. Gravitational harmonics and moment of inertia of the resulting density profiles are calculated using the Theory of Figures to order 7 (Nettelman et al., 2021). Plausible and thermodynamically consistent interior models are shown to be relatively straightforward to obtain. Using the anelastic magnetohydrodynamics code MagIC (Gastine and Wicht, 2012), examples of these interior models are implemented as the background state for dynamo models of Jupiter and Saturn.   

How to cite: Heimpel, M.: Thermodynamically consistent background state and dynamo models constrained by Juno and Cassini gravity harmonics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13983, https://doi.org/10.5194/egusphere-egu24-13983, 2024.

Recently, it has been shown that the secular variation of Jupiter's magnetic field, which has been observed by the Juno spacecraft, is in large part due to eastward advection of the Great Blue Spot (a localized, equatorial region of intense magnetic field) by fluid flow in the deep interior. More recent observations  by Juno suggest that the drift rate of the spot is varying rapidly in time. These time variations can be fit with a sinusoidal variation of the flow speed with a period of approximately four years.  Here, we discuss both the mechanism of this time variability and the constraints that its observability place on the structure and dynamics of the deep interior.

How to cite: Bloxham, J., Cao, H., Stevenson, D., Connerney, J., and Bolton, S.: Rapidly time-varying zonal flow in Jupiter's deep interior, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4667, https://doi.org/10.5194/egusphere-egu24-4667, 2024.

On July 31^st, 2023 and September 9^th, 2023, Juno performed the first studies of Jupiter’s atmosphere through radio occultation experiments since the Voyager and Galileo missions. These remote sensing experiments were conducted in a coherent two-way mode, where an uplink signal frequency was used as a reference for the downlink signals, at X and Ka band, transmitted back to the Earth.

During these experiments, the geometry of Juno's trajectory was such that the spacecraft was occulted by Jupiter as seen from Earth, therefore the radio signal, transmitted by the probe towards the DSN station, travelled through both Jupiter’s atmosphere and ionosphere. As a result, the radio signal underwent a phase shift due to the effect of refraction. Therefore, the Earth's antenna recorded a signal with a frequency different from what would have been observed if the signal had propagated through a vacuum. This difference, called Doppler residual frequency, has been used to infer the density, pressure, and temperature profiles of Jupiter’s neutral atmosphere and the electron number density of its ionosphere.

In the analysis of Jupiter’s atmosphere and ionosphere, where the assumption of spherical symmetry does not hold, the effect of oblateness cannot be neglected. Consequently, the radio data analysis cannot be performed by resorting to the traditional application of the Abel transform. Instead, a more suitable approach involves employing the ray-tracing technique.  This technique, based on the geometrical optics approximation, can also take into account the effects of zonal winds in retrieving the properties of Jupiter's atmosphere. Additionally, the use of multi-frequency link techniques allowed us to disentangle the contributions from dispersive and neutral media in the frequency shift.

This study presents an analysis of the data collected during the inaugural Juno radio occultation experiments of Jupiter. Specialized software has been developed to analyse the data acquired from these Juno-Jupiter two-way radio occultation experiments. Preliminary results of this analysis are given in terms of ionospheric electron density and atmospheric pressure-temperature profiles.

How to cite: Caruso, A., Gomez Casajus, L., Buccino, D., Gramigna, E., Parisi, M., Coffin, D., Withers, P., Zannoni, M., Smirnova, M., Galanti, E., Kaspi, Y., Tortora, P., Park, R. S., Steffes, P., and Bolton, S.: Jupiter's atmosphere through Juno's radio occultation experiments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10938, https://doi.org/10.5194/egusphere-egu24-10938, 2024.

Last year, we showed that JunoCam images, acquired in the visible, have the resolution necessary to measure the height of clouds from their projected shadows. We focused our analysis on the “Nautilus”, a 3000-km cyclonic vortex seen during Juno’s 14^th periojove. That structure consists mainly of a spiraling counter clockwise white cloud that casts a shadow onto a reddish cloud deck∼20 to 30 km below. Small individual clouds also pop out of the white cloud deck, towering about ~10 to 20 km above it. An analysis of near-simultaneous HST images of the Nautilus confirms that the white region is higher than its surrounding darker, reddish cloud deck. These respective elevations are consistent with the white clouds being made of fresh ammonia ice while most of the reddish clouds underneath are made of ammonium hydrosulfide NH₄SH, as predicted by equilibrium cloud models.

An analysis by F. Biagiotti of a similar region observed by JIRAM during Juno’s 1st perijove identifies the presence of elusive ammonia ice crystals, either pure or mixed with a nitrogen-bearing species similar to Titan’s tholins. In addition, these clouds have altitudes that are consistent with the above interpretation. However, the surrounding material is not much deeper and incompatible with NH₄SH. We discuss a possible solution to the corundum: At least in the gas, the atmosphere's optical thickness is much larger at the wavelengths used for the JIRAM study (2 to 3.2 micron)  than in the visible. The effect of scattering by cloud particles is to be evaluated, but it appears likely that altogether, infrared observations at these wavelengths cannot penetrate as deep as visible ones.

An interpretation of these observations, consistent with spectroscopic observations in the visible, is therefore that, at least in this region close to ~40°N, most of Jupiter's visible cloud deck is made of NH₄SH, that updrafts can locally deliver fresh ammonia ice but that these ammonia ice crystals remain only for a short time either because of downwelling and evaporation or because of coating.

How to cite: Guillot, T., Biagiotti, F., Davide, G., Mike, W., Leigh, F., Glenn, O., Eichstaedt, G., Rosenqvist, M., Brueshaber, S., Hansen, C., Keaveney, C., Kelly, K., Momary, T., Lunine, J., and Bolton, S.: How high are Jupiter’s clouds? From high-resolution JunoCam images to a multi-wavelength analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17351, https://doi.org/10.5194/egusphere-egu24-17351, 2024.

Our understanding of the giant planets in our solar system has been significantly advanced by the Juno and Cassini missions. These planets provide us with the unique opportunity to understand the interior structure of giant exoplanets. Recent insight into Jupiter’s atmospheric composition indicates a water concentration of 2-7 times solar in the equatorial region, surpassing the subsolar findings of the precursor Galileo mission. In this study, we conduct radiative transfer calculations for Jupiter's deep atmosphere including these enhanced water enrichment results and the presence of condensates predicted by chemical equilibrium models. Our primary focus is to derive a new temperature-pressure profile and assess the existence of potential radiative zones within the deep atmosphere. The presence of a radiative zone can have a profound impact on the internal structure of a planet and thus, a detailed analysis of Jupiter's temperature profile is essential for a comprehensive study of its interior structure.

How to cite: Siebenaler, L. and Miguel, Y.: Exploring the temperature profile of Jupiter's deep atmosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6119, https://doi.org/10.5194/egusphere-egu24-6119, 2024.

How to cite: Gavriel, N. and Kaspi, Y.: Vorticity-gradient forces and a center-of-mass approach explain the mean and oscillatory motion of Jupiter's polar cyclones., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8890, https://doi.org/10.5194/egusphere-egu24-8890, 2024.

Juno has observed the circumpolar cyclones (CPCs) on Jupiter with the visible-light camera, JunoCam, and the 2-5 µm infrared JIRAM camera, since orbit insertion.  The CPCs have distinctive cloud features, and unique characteristics that broadly classify into two morphological forms, chaotic and filled.  As revealed by JunoCam, the filled CPCs typically appear with large bright cloud features on the periphery, similar in appearance to a circular saw blade.  Just inward of those, nearly uniform darker regions appear---probably stratiform clouds---occasionally displaying small hole-like openings, which appear bright at 5 μm. The overall appearance of the periphery and just inward is reminiscent of shear-like instability in the flow. Anticyclonic circulation has been witnessed in the center of several filled CPCs. Lightning has also been observed by JunoCam in one of the blade-like cloud features at perijove 31, and we occasionally observe thin, bright curvilinear cloud features and clusters of bright clouds with shadows indicating vertical structure. The chaotic CPCs, including the central cyclone, have a different morphology, however, appearing as a flocculent and tightly wrapped series of alternatively bright and dark spirals. Interestingly, CPC #2 has partially transformed from a chaotic morphology into a filled morphology, similar perhaps to how oval cyclones and barges in the low latitudes can sometimes transform into folded-filamentary cyclones (e.g., Clyde’s Spot).

Here, we discuss each CPC and the central cyclone throughout the course of the mission thus far. We primarily use images captured by JunoCam and JIRAM, but we note that the MWR is now resolving the CPCs (see separate abstract), providing additional clues on their vertical structure. This work is an attempt to document the morphology of the CPCs and their changes for future modeling attempts to replicate them in detail, which, in turn, may provide additional insight into their formation, evolution, and stability.

How to cite: Brueshaber, S., Orton, G., Hansen, C., Levin, S., Mura, A., Grassi, D., Fletcher, L. N., Rogers, J., Eichstadt, G., Wong, M. H., and Bolton, S.: Morphological Changes in Jupiter’s Northern Circumpolar Cyclones as Revealed by JunoCam and JIRAM. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9497, https://doi.org/10.5194/egusphere-egu24-9497, 2024.

The Juno spacecraft, in extended mission, explores the environments of the Galilean satellites as it passes through Jupiter’s equator plane prior to periJove. Two close passages of Io with a minimum altitude of ~1500 km were targeted to occur on orbits 57 and 58, providing a wealth of information on Io’s interior (gravity), geologic processes, atmosphere, and interaction with Jupiter’s magnetosphere. Juno’s magnetometer investigation samples the vector magnetic field in Io’s vicinity at 64 samples/s. Here we discuss Io’s interaction with the Jovian magnetosphere and the detection of ion cyclotron waves at ~0.5 Hz, ~1 Hz, and ~2 Hz, associated with Io-genic SO₂, S, and O.

How to cite: Connerney, J., Gershman, D., jorgensen, J., Herceg, M., Kotsiaros, S., and Saur, J.: Magnetic Field Observations During the Juno Spacecraft’s Close Passages of Io, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12605, https://doi.org/10.5194/egusphere-egu24-12605, 2024.

Juno’s Extended Mission has expanded the scientific reach of Juno’s low-light Stellar Reference Unit (SRU) star camera to multiple new targets within the Jovian system. Close flybys of the dark sides of Ganymede and Europa (illuminated by Jupiter-shine) have yielded high-resolution SRU surface images that enabled significant improvements to the geomorphologic maps of these icy moons and revealed sites of potential present day surface activity on Europa (providing high quality baselines for Europa Clipper and JUICE). Close flybys of Jupiter’s dark side began in Spring 2023, launching the SRU’s Extended Mission study of lightning in the northern latitudes at resolutions as high as a few kilometers per pixel, and the geometry has also allowed the SRU to image Jupiter’s faint dust ring from vantage points inside the ring. The Mission’s planned flybys of Io in December 2023 and February 2024 will present additional opportunities for low-light high-resolution SRU surface imaging on the dark side of the volcanic moon. Our presentation will discuss new Extended Mission results from Juno’s SRU. 

How to cite: Becker, H. N., Florence, M., Brennan, M., Lunine, J., Schenk, P., Hansen, C., Martos, Y., Bolton, S., and Alexander, J.: New Extended Mission Results from Juno’s Stellar Reference Unit , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3269, https://doi.org/10.5194/egusphere-egu24-3269, 2024.

Currently in its first extended mission, NASA’s Juno spacecraft has made several close approaches to Jupiter’s Galilean satellites.  The final of these very close flybys will be of Io during the perijove (PJ) 58 orbit, scheduled to occur at 17:48:35 UTC on 3 Feb. 2024, about 3^h59^m prior to PJ58. Juno’s Ultraviolet Spectrograph (UVS) is a photon-counting far-ultraviolet (FUV) imaging spectrograph with a bandpass of 68-210 nm, which will be used to observe Io’s numerous FUV emissions during the flyby. The circumstances of the flyby are similar to that for Ganymede during PJ34 at 16:56 UTC on 7 June 2021, with the satellite only observable for a few minutes on either side of Juno’s closest approach. We plan to record data +/-5 min (at best 20 swaths of data) about the closest approach time hoping for a significant decrease in the high radiation background due to shielding provided by Io itself.  Our observations will range from an altitude of 1500 km (closest approach) to 7820 km, giving the UVS data an expected spatial resolution of 6 to 28 km at the sub-spacecraft point.  As with the similar close flyby of Ganymede (Greathouse et al. 2022; Molyneux et al. 2022), UVS will attempt to measure reflected FUV sunlight from the surface of Io and airglow emissions from oxygen and in this case sulfur atoms. These observations will be more challenging than at Ganymede, however, since the background due to penetrating (>10 MeV) electrons at Io is expected to be a factor of 10 or more larger than at Ganymede. In this talk we will present results from the initial reduction and analysis of the UVS data obtained during the flyby of Io.

How to cite: Greathouse, T., Gladstone, R., Hue, V., Versteeg, M., Kammer, J., Giles, R., Bonfond, B., Grodent, D., Gerard, J.-C., Bolton, S., and Levin, S.: Juno-UVS Observations of Io during the PJ58 Flyby, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10142, https://doi.org/10.5194/egusphere-egu24-10142, 2024.

NASA’s Juno mission has been observing Jupiter since 2016 from a polar, highly elliptical orbit. Although not in the main scientific objectives, Juno took images and spectra of the Galilean moons from a very favourable position, using some of the cameras on board: JIRAM,  JunoCam and SRU. JIRAM, the Jovian InfraRed Auroral Mapper, is a dual-band imager and spectrometer in the infrared (2000-5000 nm); JunoCam is a visible color imager;  SRU is Juno's Stellar Reference Unit, a highly sensitive, visible  wavelength (450-1100 nm) camera.
JIRAM's imager channel is a single detector with 2D capability and with 2 different filters (L band, from 3.3 to 3.6 µm; M band, from 4.5 to 5 µm). The pixel angular resolution (0.01°) is fine enough for imaging the moons from Juno; the spatial resolution at the surface of the moons varies along the s/c distance and was of the order of 100 km/pixel at the beginning of the campaign, but it's now getting better, down to ~ 500 m. Here we focus on the study of JIRAM’s high resolution images, which can characterize the location, morphology, and some temperatures, of the volcanic thermal sources; comparison with images in the visible range is also performed.

How to cite: Mura, A., Tosi, F., Zamboni, F., Lopes, R. M., Rathbun, J., Mouginis-Mark, P., Becker, H. N., Hansen-Koharcheck, C., Sordini, R., Pettine, M., Piccioni, G., Sindoni, G., Plainaki, C., and Adriani, A.: JIRAM's observations of Io during closest approaches, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13056, https://doi.org/10.5194/egusphere-egu24-13056, 2024.

On June 7, 2021, and September 29, 2022, the NASA Juno spacecraft flew by Jupiter’s Galilean moons, Ganymede, and Europa, respectively.  The closest approach distance was only ~1000 km above Ganymede, and only ~350 km above Europa. More recently, on December 30, 2023, Juno passed by Io at a distance of 1500 km and is planned do so a second Io flyby on February 3, 2024 at a similar distance.  The close flybys were the first encounters with the moons in over two decades and provided the first opportunity to map the subsurface of the their shells at multiple microwave frequencies using Juno’s Microwave Radiometer (MWR).  The observations provided several swaths across the moons at six frequencies, ranging from 600 MHz to 22 GHz.  The ice transparency at microwave frequencies is dependent on its purity; assuming pure ice, the observations probe depths ranging from meters to kilometers. The MWR observations represent the first resolved interrogation of Ganymede and Europa’s subsurface ice shell revealing new constraints on porosity, fracturing, differences in terrain type and possibly the thickness of the ice shell. These unprecedented measurements of Io, Europa and Ganymede will allow comparative studies of the surfaces and subsurface structures of the Jovian satellites. The Juno MWR measurements complement previous ground-based radar and microwave radiometry observations, which provided early characterization of these surfaces.  A comparison of the microwave spectra for all three satellites will be presented, as well as a detailed analysis and interpretation of the Ganymede MWR data that provide new constraints on ice subsurface properties.

How to cite: Ermakov, A., Bolton, S., Zhang, Z., Levin, S., Akiba, R., Lunine, J., Feng, J., Hand, K., Keane, J., Misra, S., Hartogh, P., Stevenson, D., Siegler, M., and Bonnefoy, L.: Juno Microwave Radiometer Observations into the Subsurface of the Ice Shells of Io, Europa and Ganymede, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6820, https://doi.org/10.5194/egusphere-egu24-6820, 2024.

Juno flew less than 360 km from the surface of Jupiter’s moon Europa on 29 September, 2022, and mapped part of the ice shell with the Microwave Radiometer (MWR) at frequencies of 0.6, 1.2, 2.5, 4.8, 9.6, and 22 GHz.  The partial map covers a latitude range from ~20^oS to ~50^oN and a longitude range from 70^oW to 50^oE.  At these frequencies, the emission originates well beneath the nearly-transparent surface, probing from as deep as 28 km (at 0.6 GHz) and less than 20 m (at 22 GHz), depending on the purity of the ice.  Microwave reflection plays an important role, and MWR data suggest the presence of small (radius a few cm) scatterers at depths of many meters.  Spatial variation is dominated by reflection, especially for the higher-frequency channels, and correlates with terrain type.  We present analysis of the data and discuss the implications. 

How to cite: Levin, S., Zhang, Z., Bolton, S., Brown, S., Ermakov, A., Akiba, R., Misra, S., Hartogh, P., and Stevenson, D.: Juno Microwave Radiometer Observations of Europa’s Subsurface Ice Shell, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12983, https://doi.org/10.5194/egusphere-egu24-12983, 2024.

The NASA Juno mission performed two close fly-bys of Jupiter’s moon Io on December 30, 2023 and February 3, 2024. Juno carries a 6-channel microwave radiometer (MWR) operating between 0.6-22 GHz. The first fly-by observed Io’s north pole and the 2^nd pass mapped latitudes within +/- 45^o on the Jovian facing hemisphere. The broad frequency range of the MWR probes successively deeper into the Io sub-surface with the 0.6GHz channel probing the deepest.  The sub-surface temperature, dielectric and surface roughness properties are encoded in the spectra obtained by the MWR. Here we report on the first spatially resolved observations of Io at frequencies below 22 GHz.  We find the brightness temperatures decrease with increasing latitude and are coldest at the north pole, consistent with prior infrared observations of the surface skin temperature. We observe a strong spectral gradient in the lowest frequency channels (increasing with depth) reflecting the sub-surface temperature profile from which we can infer endogenic heat flow. We will give an overview of the MWR observations and initial inferences about the sub-surface thermal and compositional properties.    

How to cite: Brown, S., Bolton, S., Levin, S., Zhang, Z., Siegler, M., and Feng, J.: Observations of Io with the Juno Microwave Radiometer:  First Results and Implications for Global Heat Flow, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13536, https://doi.org/10.5194/egusphere-egu24-13536, 2024.

Ganymede’s atmosphere is one of the most complex among the moons of our solar system. As the only known satellite in our solar system to feature an intrinsic global magnetic field, Ganymede forms a small magnetosphere within the much larger magnetosphere of Jupiter. The interaction between the two magnetospheres makes Ganymede's plasma environment highly variable both in space and time. Consequently, the moon's atmosphere, predominantly shaped by the interplay between the plasma environment and Ganymede's surface, likely exhibits a corresponding high degree of variability.

The recent Juno spacecraft flyby of Ganymede has provided us with unprecedented insights into the moon's electron and ion environment. This study capitalizes on electron data collected by the Jovian Auroral Distributions Experiment (JADE) during Juno's traversal of Ganymede's magnetopause current layer, employing these measurements as a proxy for the electron conditions within Ganymede's auroral region. Our simulations reveal that these electrons play a pivotal role in governing Ganymede's H₂ and O₂ atmospheres, representing the predominant constituents of its atmospheric composition. Furthermore, the abundance of atomic O and H, crucial factors in Ganymede's atmospheric mass loss, is intricately influenced by these electrons, underscoring their significance in shaping the complex dynamics of Ganymede's atmospheric behavior.

Our current understanding of Ganymede's atmosphere predominantly stems from spectroscopic observations. However, it's crucial to acknowledge that the interpretation of spectroscopic data heavily relies on certain assumptions. Our analysis underscores the significance of acquiring a comprehensive understanding of Ganymede's atmosphere. To achieve this, it is imperative to conduct simultaneous observations encompassing the moon's surface, its atmospheric conditions, and the entirety of its plasma environment, including both thermal and energetic ions and electrons. 

How to cite: Vorburger, A., Fatemi, S., Carberry Mogan, S. R., Galli, A., Liuzzo, L., Poppe, A. R., Roth, L., and Wurz, P.: Influence of Ganymede's electron environment as measured by JADE on Ganymede's atmosphere, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6024, https://doi.org/10.5194/egusphere-egu24-6024, 2024.

The inward plasma transport at Saturnian magnetosphere is examined using the flux tube interchange stability formalism developed by Southwood and Kivelson (1987).  Seven events are selected.  Three cases are considered: (1) the injected flux-tube and ambient plasmas are nonisotropic; (2) the injected flux-tube and ambient plasmas are isotropic and (3) the injected flux-tube plasma is isotropic but the ambient plasma is nonisotropic.  Case (1) may be relevant for fresh injections while case (3) may be relevant for old injections.  For cases (1) and (2), all but one events have negative stability condition, suggesting that the flux-tube should be moving inward.  For case (3), the injections located at L > 11 have negative stability condition, while 4 out of 5 of the injections at L < 9 have positive stability condition.  The positive stability condition for small L suggests that the injection may be near its equilibrium position and possibly oscillating thereabouts---hence the outward transport if the flux tube overshot the equilibrium position.  The flux-tube entropy plays an important role in braking the plasma inward transport.  When the stability condition is positive, it is because the entropy term, which is positive, counters and dominates the effective gravity term, which is negative for all the events.  The ambient plasma and drift out from adjacent injections can affect the stability and the inward motion of the injected flux tube. The results have implications to inward plasma transport in Jovian magnetosphere as well as other fast rotating planetary magnetospheres.

How to cite: Wing, S., Thomsen, M., Johnson, J., Ma, X., Mitchell, D., Allen, R., and Delamere, P.: The roles of flux-tube entropy and effective gravity in the inward plasma transport at Saturn, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2951, https://doi.org/10.5194/egusphere-egu24-2951, 2024.

High energy particle fluxes (>15MeV e- and 120MeV p+) throughout the Jovian magnetosphere have been continuously measured by the MAG investigation’s ASC instrument. Juno’s highly elliptical polar orbit has effectively traversed almost all of the Jovian magnetosphere with most regions sampled multiple times over time. Pronounced variations in the observed flux for comparable regions of the magnetosphere are observed in association with the positions of the Galilean moons and their associated dust and plasma tori, while global variations appear to be coupled to magnetic compression due to corona mass ejections. Oversampling of specific regions affords the opportunity to compile a quiet time map of the energetic trapped particle environment despite variations in solar activity and satellite-related effects. Subtracting this quiet time flux from that observed yields detailed information on the impact of solar activity, the Galilean moons, and the gossamer rings on the high-energy trapped particle environment of Jupiter. We present the observed quiet time map and show the impact on the trapped high-energy flux from the abovementioned local sources and sinks, and compare these results to those observed by Pioneer 10 and 11.

How to cite: Jørgensen, J., Denver, T., Herceg, M., Sushkova, J., Jørgensen, P., Connerney, J., and Bolton, S.: A detailed map of the Jovian high-energy radiation belts, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20547, https://doi.org/10.5194/egusphere-egu24-20547, 2024.

A common problem in space physics is how the energetic particles we observe in space are accelerated to high energies. In the magnetospheres and radiation belts of magnetized planets like the Earth and Saturn, we find electrons with up to MeV energies. There are two fundamental acceleration processes. Electrons can gain energy when they are transported closer to the planet (radial acceleration), where the magnetic field is stronger. The alternative is that the electrons are accelerated locally, through fluctuating electric or magnetic fields and wave-particle interaction. In this work, we use a modified version of the Versatile Electron Radiation Belts code to perform the simulations of the radiation belts at Saturn. Using convection terms of a modified Fokker-Planck equation, the zebra stripes and banana orbit signature is reproduced in the convection-diffusion code. Using the flexibility of our simulation framework, we explore the effects of radial diffusion, coulomb scattering and the local diffusion. Throughout the series of simulations, we aim to understand the role of the controlling processes of the radial transport acceleration (e.g., due to variable electric field) and the role of local acceleration, as well as any other processes needed to reproduce the observations.

How to cite: Drozdov, A., Kollmann, P., Hao, Y., and Wang, D.: Modeling of Saturn’s radiation environment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2578, https://doi.org/10.5194/egusphere-egu24-2578, 2024.