Juno’s microwave radiometer has revolutionized our understanding of Jupiter’s atmosphere. By utilizing six microwave channels (0.6 GHz ~ 22 GHz), Juno has scanned Jupiter’s atmosphere from pole to pole, providing near-global, three-dimensional coverage. While the primary goal was to measure water abundance beneath the cloud layer, the data have revealed far more, raising new questions. Notably, the radiometer shows that Jupiter’s weather layer is not generally adiabatic, challenging prior assumptions that convection would homogenize entropy. Furthermore, three distinct atmospheric regions on Jupiter have emerged: the tropics, the mid-latitudes, and the polar regions. The tropics exhibit a distinct temperature structure that features a super-adiabatic temperature gradient across the water condensation level. In the mid-latitudes, the ammonia gas has maintained a vertical gradient down to depths of 50 –100 bars despite vigorous convective mixing. Only the regions near Jupiter’s north pole – perhaps near the south pole as well – closely resemble the long-anticipated moist adiabatic state. This presentation will summarize key findings from Juno’s microwave experiment, spanning both the prime and the extended mission, and highlight significant revisions to our understanding of Jupiter’s atmosphere. We will also discuss the implications for future missions to Saturn, Uranus, and Neptune based on Juno’s microwave results.
How to cite: Li, C., Atreya, S., Fletcher, L., Hu, J., Ingersoll, A., Li, L., Lunine, J., Orton, G., Oyafuso, F., Steffes, P., Wong, M., Zhang, Z., Levin, S., and Bolton, S.: Juno’s microwave sounding of Jupiter’s atmosphere from pole to pole, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7793, https://doi.org/10.5194/egusphere-egu25-7793, 2025.
The Juno extended mission (2023–2025) offers a unique opportunity to study Jupiter’s atmosphere by radio occultations. In these experiments, the atmospheric refractivity and the bending angle affecting a radio signal crossing a planetary atmosphere can be inferred by analyzing the Doppler shift induced on the downlink frequencies, at X and Ka bands, recorded at NASA Deep Space Network stations. The analysis is conducted using a ray-tracing-based inversion algorithm that accounts for Jupiter’s oblateness and the effects of zonal winds.
The objectives of these experiments are to measure pressure-temperature profiles across different depths and latitudes of the Jovian atmosphere, with the goal of understanding its complex dynamics. Also, radio occultations’ results may help us understand the structure of the ionosphere, particularly in polar regions, by exploiting the availability of sky frequencies recorded at two different bands, X and Ka, to isolate the dispersive contribution to the Doppler shift. These ionospheric results aim at investigating the aurora’s influence on the rest of the planet.
Starting with perijove 63 in July 2024, Juno’s radio occultations have started probing the polar regions above 60°N, including areas near the auroral zones. The aim of this work is to present the results of the analysis of recent polar occultations, providing pressure-temperature profiles of the neutral atmosphere and electron density profiles of the ionosphere. Additionally, we present the results of an error quantification analysis, which accounts for various factors such as noise in the Doppler observables, uncertainties in wind measurements, unknown boundary value of temperature at a specific pressure level, and uncertainties in Juno's trajectory. This comprehensive analysis allows us to evaluate the uncertainties associated with the computed atmospheric profiles. As Juno continues its extended mission, ongoing radio occultation experiments will further refine these results, shedding new light on the intricate dynamics and structure of Jupiter’s atmosphere.
How to cite: Caruso, A., Gomez Casajus, L., Smirnova, M., Coffin, D., Buccino, D., Galanti, E., Gramigna, E., Parisi, M., Togni, A., Zannoni, M., Tortora, P., Park, R. S., Kaspi, Y., Withers, P., Hubbard, W., Steffes, P., and Bolton, S.: Radio Occultations with Juno: Unveiling the Structure of Jupiter’s Polar Atmosphere and Ionosphere, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16362, https://doi.org/10.5194/egusphere-egu25-16362, 2025.
How to cite: Gavriel, N. and Kaspi, Y.: Dynamical Constraints on the Vertical Structure of Jupiter's Polar Cyclones, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8579, https://doi.org/10.5194/egusphere-egu25-8579, 2025.
Understanding Jupiter's internal structure is crucial for uncovering its formation and evolutionary history, providing valuable constraints that have broader implications for other giant planets and the Solar System. The primary observational data used to constrain Jupiter’s interior come from precise gravity field measurements by NASA's Juno mission, atmospheric data from both Juno and the Galileo entry probe, and Voyager radio occultations. However, these observations are limited compared to the vast range of plausible interior configurations and their associated parameters, making it challenging to reconcile the data with theoretical models.
In this study, we use NeuralCMS, a deep learning model based on the concentric Maclaurin spheroid (CMS) method, coupled with a self-consistent wind model to efficiently explore a wide range of interior models without prior assumptions. This integrated approach allows us to identify models consistent with the available measurements. We apply it to determine the permissible range of the dynamical contribution to the gravity field from Jupiter's dilute core model, demonstrating that our modeling approach provides tighter constraints on recently published, widely considered interior models.
Using clustering techniques on the full multidimensional dataset of plausible interior structures, we identify four charachteristic interior structures distinguished by their envelope and core properties (dilute and compact). Our results show that Jupiter’s interior can be effectively described using only two key parameters, significantly reducing the dimensionality of the problem. We also highlight the most observationally constrained interior structures and show that they might be confined to one of the identified key structures.
Our framework establishes a baseline for using deep learning models to constrain planetary interiors based on gravity data, offers a self-consistent approach to coupling interior and wind models, and provides valuable insights into the multidimensional nature of the problem. This approach can also enable meaningful comparisons with interior models of other giant planets.
How to cite: Ziv, M., Galanti, E., Howard, S., Guillot, T., and Kaspi, Y.: Characterizing Jupiter's interior using machine learning reveals four key structures, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8235, https://doi.org/10.5194/egusphere-egu25-8235, 2025.
The shape of Jupiter is determined primarily by the planet’s rotation rate. Additionally, its interior density distribution plays an important role in defining its detailed shape. These characteristics can be used to calculate the gravitational potential. Then, the shape can be estimated using some estimate of either the polar or the equatorial radius of a specific pressure level, such as the 1 bar or 100 mb level. The shape is also affected by the zonal winds, creating a primarily positive anomaly in the order of 10 km at low latitudes. However, uncertainties in the observed cloud-level wind and the polar radius translate to an uncertainty in the shape with the same order of magnitude. Moreover, until now, only a few radio occultations, to which a shape estimate can be compared, have been performed, three by the Voyager spacecraft and three by the Pioneer spacecraft.
During the past year, the Juno mission performed a series of radio occultation measurements, enabling a more exact calculation of Jupiter's shape. Using these measurements, we calculate a new shape for Jupiter at the 100 mb pressure level. We then examine our results with respect to earlier shape estimations, mainly to the work of Lindal et al. (1981), and find a new, entirely consistent solution for the shape at the 1 bar level, the most commonly used level for the shape of Jupiter. These results bear importance for a wide range of research studies, from the interior modeling of Jupiter and other giant planets to the study of exoplanets.
How to cite: Galanti, E., Kaspi, Y., Smirnova, M., Ziv, M., Fonsetti, M., Caruso, A., Zannoni, M., Tortora, P., Hubbard, W., Buccino, D., Parisi, M., Park, R., Militzer, B., Steffes, P., Levin, S., and Bolton, S.: The shape of Jupiter in light of the Juno radio occultation measurements, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5771, https://doi.org/10.5194/egusphere-egu25-5771, 2025.
The Juno spacecraft continues to map the gas giant’s complex magnetic field with ever-increasing resolution in space and time, taking advantage of the natural evolution of Juno’s polar orbit and time on target. At the beginning of the prime mission in 2016, Juno’s cloud-topping periapsis occurred 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. Our recent spherical harmonic models derived from Juno measurements through orbit 66 of Extended Mission 1 (EM1, periJove at 56 degrees north latitude) routinely introduce a correction to the planet’s rotation period along with resolution of spherical harmonic coefficients corresponding to smaller spatial scales. Jupiter’s planetary rotation period (per IAU) has been determined with greater accuracy than that provided by observations of its radio emissions (System III (1965): 9h 55m 29.711s +/-0.04s). The secular variation of the magnetic field during Juno’s mission through orbit 66 (by ~0.122°/yr) yields an improved planetary rotation period of 9h 55m 29.697s, if the variation is attributed to the limited accuracy of the IAU adopted planetary rotation period. Much of the apparent motion of the Great Blue Spot (GBS), the localized patch of intense magnetic field near the equator, can be accounted for by inaccuracy of System III (1965). As Juno’s periJove migrates further northward in EM1 (through orbit 76) and EM2, the polar regions will be mapped at lower altitudes affording comparison with fluid motions such as those probed by Juno’s Microwave Radiometer (MWR). The latter half of EM1 orbits will complete mapping of the mid latitude high flux band, and EM2 will map the field with periJoves to 81 degrees north latitude where the circumpolar cyclones encircle the pole.
How to cite: Connerney, J., Timmins, S., Jorgensen, J., Bloxham, J., Bolton, S., and Levin, S.: Jupiter’s Magnetic Field and Rotation Period in the Extended Missions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7451, https://doi.org/10.5194/egusphere-egu25-7451, 2025.
As has been recognized since the completion of Juno’s first nine orbits, Jupiter’s magnetic field is morphologically distinct from that of the other planets. Six years later, with over 50 additional orbits, that picture has not fundamentally changed. While, like Earth, the field has a strong axial dipole component, the most intense field occurs in two distinct regions: the Great Blue Spot (GBS) and the Northern Hemisphere Flux Band (NHFB). Elsewhere, there are large regions of very low flux. What processes drive this field morphology? While the axial dipole is almost certainly the result of a global dynamo (though of uncertain depth extent), these other features likely result from more localized dynamical processes. We consider various possibilities to explain the GBS, including flux expulsion, but only concentration of flux by a convergent (i.e. downwelling) flow seems plausible. For the NHFB, enhanced convection at the outer edge of the tangent cylinder to a deep stably stratified region is one possibility, though this does not explain the lack of such a feature in the southern hemisphere. Here, too, flux concentration by convergent flow is also a possibility. The regions of low flux may indicate the regions from which flux has been swept by divergent flow towards the regions of convergent flow. We will also discuss whether such processes are consistent with predominantly zonal flow in the presence of possible stable stratification.
How to cite: Bloxham, J., Cao, H., Stevenson, D., Connerney, J., and Bolton, S.: Towards an understanding of the morphology of Jupiter’s magnetic field, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3744, https://doi.org/10.5194/egusphere-egu25-3744, 2025.
Jovian auroras, the most intense in the Solar System, arise from interactions between Jupiter’s magnetosphere and atmosphere. While their horizontal morphology has been extensively studied, their vertical structure, shaped by the penetration depth of magnetospheric electrons, remains less well understood. Previous observations, including those from the Hubble Space Telescope (HST), have provided only partial insights into this aspect. This study aims to characterize the vertical structure of Jovian auroral emissions.
We analyzed observations from Juno’s UltraViolet Spectrograph (UVS) to examine the altitude and horizontal distribution of auroral emissions. Building on recent studies that mapped the average energy of precipitating electrons in auroral regions, we explored the relationship between this energy and the volume emission rate (VER) of H₂. Our analysis considers two types of electron energy distributions: monoenergetic and a kappa distribution with κ = 2.5.
By leveraging brightness maps, we reconstructed the three-dimensional VER structure of Jovian auroras in both hemispheres across multiple spacecraft perijoves (PJs). For PJ11, we found that in the polar emission region, the average altitude of the VER peak is approximately 250 km for the monoenergetic case and 190 km for the kappa distribution. In the main emission region, the average altitude is around 260 km for the monoenergetic case and 197 km for the kappa distribution. Similar results were obtained for other PJs.
Our findings align, on average, with measurements from the Galileo probe and HST observations, reinforcing the value of Juno data in probing the vertical structure of auroral emissions. Given the variability of the κ parameter in auroral regions, we assessed its impact on the altitude distribution of emissions. Our sensitivity analysis indicates that κ variability has a minor effect on the peak altitude of the VER but does influence the amplitude, suggesting potential effects on the thermal structure and chemical composition of Jupiter’s auroral regions.
How to cite: Benmahi, B., Bonfond, B., Benne, B., Hue, V., Grodent, D., Barthélemy, M., Sinclair, J. A., Moirano, A., Head, L. A., Gladstone, R., Gronoff, G., Sicorello, G., Simon-Wedlund, C., Giles, R., and Greathouse, T. K.: Reconstruction of the 3D Auroral Structure Using Juno/UVS Observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3530, https://doi.org/10.5194/egusphere-egu25-3530, 2025.
At Jupiter, the fast planetary rotation, the strong magnetic field and the presence of a relatively high density plasma create a powerful electromagnetic environment. Jupiter’s auroras are one evidence of the strong magnetospheric activity around the planet. The interaction between the four major moons of Jupiter - Io, Europa, Ganymede and Callisto - and the Jovian magnetosphere produces satellite-induced auroral emissions, called footprints. These are caused by the flow of magnetospheric plasma past the moons, which triggers a local perturbation that generates mainly Alfvén waves propagating down to the planetary atmosphere. Here, the Alfvén waves accelerate electrons into the ionosphere, where auroral emissions are generated. The morphology of the footprints depends on the shape of the wave-fronts of the Alfvén waves that bounce in the magnetospheric cavity. The propagation of these waves is mainly affected by the magnetic field and plasma density, therefore, the footprint implicitly contains information on those quantities.
Since 2016, the Juno mission has been providing high-quality observations of the Io footprint in the infrared (IR) and ultraviolet (UV) bands. We propose an overview of the IR and UV observations of the footprints from Juno, with a particular focus on Io, to highlight how the observations of the footprints can fulfill multiple purposes, such as monitoring plasma conditions in the magnetosphere, and investigating the vertical structure of the ionosphere. We show the comprehensive dataset of the observations, which is compared to previous observations from Hubble and to magnetic field models. The agreement with the magnetic field model based on the Juno magnetometer is overall very good, with the major deviations in the northern anomaly region. The position of the footprints can be used to constrain the plasma conditions at the orbit of the moons, therefore we use the IR and UV observations of the Io footprint to determine the density and temperature of the Io Plasma Torus around Jupiter between 2016 and 2022. To support this survey, the radio occultations performed by the radio tracking systems have been included, as they wrap information on the electron content of the Io Plasma Torus. This analysis suggests that the Io Plasma Torus can exhibit large variations (factor ~2-3) in density and temperature over a couple of months. We are currently investigating the UV vertical profile of the Io footprint by using limb observations, which allow to constrain the energy distribution of the precipitating particles and the energy deposition, and the location of the methane homopause, which absorbs part of the UV emission and destroy the H3+ responsible for the IR emission.
How to cite: Moirano, A., Bonfond, B., Mura, A., Hue, V., Caruso, A., Benmahi, B., Grodent, D., Head, L. A., Gérard, J.-C., Sicorello, G., Greathouse, T. K., Gomez Casajus, L., Tortora, P., and Zannoni, M. and the the JIRAM team: The moon-induced auroral emissions at Jupiter:a natural probe of the atmosphere and magnetosphere, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12252, https://doi.org/10.5194/egusphere-egu25-12252, 2025.
The magnetospheric cusp connects the planetary magnetic field to interplanetary space, offering opportunities for charged particles to precipitate to or escape from the planet. Terrestrial cusps are typically found near noon local time, but the characteristics of the Jovian cusp are unknown. Here for the first time we show direct evidence of Jovian cusps using datasets from multiple instruments onboard Juno spacecraft. We find that the cusps of Jupiter are in the dusk sector, which is contradicting Earth-based predictions of a near-noon location. Nevertheless, the characteristics of charged particles in the Jovian cusps resemble terrestrial and Saturnian cusps, implying similar cusp microphysics exist across different planets. These results demonstrate that while the basic physical processes may operate similarly to those at Earth, Jupiter’s rapid rotation and its location in the heliosphere can dramatically change the configuration of the cusp. This work provides significant insights into the fundamental consequences of star-planet interactions, highlighting how planetary environments and rotational dynamics influence magnetospheric structures.
How to cite: Xu, Y., Arridge, C., Yao, Z., Zhang, B., Ray, L., Badman, S., Dunn, W., Ebert, R., Chen, J., Allegrini, F., Kurth, W., Qin, T., Connerney, J., McComas, D., Bolton, S., and Wei, Y.: In Situ Evidence of the Dusk-side Cusp of Jupiter from Juno Spacecraft Measurements, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14769, https://doi.org/10.5194/egusphere-egu25-14769, 2025.
Until now, in-depth analysis of the microphysics associated with high Mach number astrophysical bow shocks has not been feasible. Although previous spacecraft have passed through the bow shocks of outer planets, their onboard instruments were not equipped or designed to capture high-resolution data focused on the shock, which spans several electron inertial lengths. However, beginning in late 2024, an enhanced algorithm on Juno enabled high-resolution observations of Jupiter's bow shock. This paper details the initial observations of plasma waves in the vicinity of the shock, which encompass lower hybrid waves, electron cyclotron drift instability, electrostatic solitary waves, and Langmuir waves. Additionally, we present magnetic field and particle data to provide a comprehensive understanding of the phenomena.
How to cite: Joseph, J., Kurth, W., Hospodarsky, G., Connerney, J., Sulaiman, A., Wilson, R., Piker, C., and Bolton, S.: Microphysics of Jovian bow shock - a plasma wave perspective., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12528, https://doi.org/10.5194/egusphere-egu25-12528, 2025.
This study performs a comprehensive investigation of Jupiter’s multispecies plasma that fill its extensive and dynamic magnetosphere. In particular, we analyze energetic ion data from Juno’s Jupiter Energetic particle Detector Instrument (JEDI). Specifically, we use measurements from the JEDI-090 and JEDI-270 identical instruments, which provide measurements for the energy, angular, and compositional distributions of hydrogen (∼50 keV to ∼1 MeV), oxygen (∼170 keV to ∼2 MeV) and sulfur (∼170 keV to ∼4MeV) ions. In this survey, we present comprehensive ion maps derived from the entire Juno prime mission (orbits 1 to 34) and spanning all available energy channels, when the spacecraft explored the dawn to pre-midnight sector of Jupiter's magnetosphere. These maps reveal the spatial and energetic distributions of hydrogen, oxygen, and sulfur ions, providing insights into the global magnetodisk structure, and ion distributions in both equatorial and off-equatorial regions. As part of our ongoing work, we also calculate the H/O and H/S ion composition ratios and assess the spectral indices to characterize the energization processes of these ion populations. With this work, we aspire to highlight Juno’s transformative contribution to advancing our understanding of Jupiter’s magnetosphere and its broader implications for comparative planetary studies.
How to cite: Moutsiana, G., Clark, G., Gkioulidou, M., Daglis, I., and Mauk, B.: Comprehensive Mapping and Statistical Analysis of Energetic Ion Distributions in Jupiter’s Magnetosphere Using Juno/JEDI Data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14990, https://doi.org/10.5194/egusphere-egu25-14990, 2025.
Juno’s highly elliptical polar orbits have enabled groundbreaking in-situ observations of the electrodynamic interaction between Jupiter and its volcanic moon, Io. These observations probe previously unexplored regions, including Io’s orbit, Jupiter’s ionosphere, and the intermediate space between them. Magnetic field data from multiple Juno traversals of field lines connected to Io’s orbit reveal intricate and dynamic magnetic signatures near flux tubes associated with Io’s position. This study introduces a methodology for modeling the distribution of currents along Io’s flux tube (IFT) and Alfvén wings, replicating the observed magnetic field signatures during Juno’s downstream encounters. We characterize the location, size, and morphology of the current-carrying regions and the current distribution within the IFT and Alfvén wings. The analysis reveals strong filamentation of field-aligned currents, with upward and downward currents splitting into secondary cells rather than forming uniform structures. A robust correlation between total field-aligned current intensity, particle energy flux, and Poynting flux highlights efficient energy transfer within the Jupiter-Io system. Using data from all Juno traversals up to perijove 42, we estimate the strength of this interaction, accounting for factors such as Io’s position within the plasma torus, its distance along the extended tail, and the magnetic field intensity at Jupiter’s ionospheric footprint. These findings provide critical new constraints on the complex interplay of electrodynamic processes in the Io-Jupiter system, advancing our understanding of magnetosphere-moon interactions in planetary environments.
How to cite: Kotsiaros, S., Connerney, J. E. P., Saur, J., Herceg, M., Martos, Y. M., Schlegel, S., and Bolton, S. J.: The Electrodynamic Interaction Between Io and Jupiter: Insights from Juno Observations , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17912, https://doi.org/10.5194/egusphere-egu25-17912, 2025.
In 2023 and 2024, the orbital evolution of Juno’s Extended Mission created unprecedented opportunities for high-resolution imaging of Io’s surface and the high northern latitudes of Jupiter. The Mission’s low-light Stellar Reference Unit (SRU) star camera captured the night sides of both bodies at wavelengths extending from the visible into the near infrared (450-1,000 nm; with peak sensitivity from ~570-800 nm). Juno’s highest resolution image of Io’s surface was acquired by the SRU during a close flyby in December 2023 at 895-1230 m pixel scale under high phase Jupiter-shine illumination. The sensitivity of the SRU at longer wavelengths enabled the first detection of thermal emission from an active lava channel on Io, corroborated by earlier lower-resolution JIRAM data at 4.78 microns. The SRU detected multiple additional thermal emission signatures from active lava breakouts in fresh flows at Zal Patera, and at the base of a vertical mountain fracture at South Zal Mons (suggesting volcanism induced by mountain tectonics). Recent observations of Jupiter’s night side have provided glimpses into the vertical structure of Jupiter’s northern aurora at <10 km/pixel and high altitude haze on Jupiter’s limb. Our presentation will discuss these Io and Jupiter findings, revealed by the SRU in low-light.
How to cite: Becker, H., Schenk, P., Lopes, R., Mura, A., Tosi, F., Florence, M., Brennan, M., Lunine, J., Ravine, M., Hansen, C., Bolton, S., and Alexander, J.: From channelized lava on Io, to Jupiter’s upper atmosphere and aurora: Juno SRU observations of emissions in the visible to near infrared, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2905, https://doi.org/10.5194/egusphere-egu25-2905, 2025.
JIRAM (Jovian Infrared Auroral Mapper) is an imager/spectrometer
onboard Juno, primarily designed for studying Jupiter's atmosphere and
auroral emissions. During its mission, JIRAM also obtained extensive
data on Io, the most volcanically active body in the solar system. The
instrument combines imaging and spectroscopy in a single device. The
imager operates in two bands: the "L" band (~3.3 to 3.6 µm), which primarily
detects surface albedo, and the "M" band (~4.5 to 5 µm), optimized for
mapping thermal structures. The spectrometer covers a range of 2 to 5
µm with a spectral resolution of 9 µm. With an angular resolution of
0.01°/pixel, JIRAM achieved a spatial resolution of up to 300 m during
close flybys of Io.
This work summarizes JIRAM’s observations of Io during the first 62
Juno orbits, and in particular the last ones, where the observation
conditions were more favourable. Detailed thermal maps reveal a
multitude of volcanic hotspots, including ring-shaped near-infrared
emissions from numerous lava lakes. The evolution of Loki Patera, the
largest and most active lava lake on Io, was monitored over nearly two
years, providing new insights into its thermal characteristics. These
observations contribute significantly to our understanding of Io’s
dynamic volcanism and thermal processes
How to cite: Mura, A., Zambon, F., Tosi, F., Lopes, R., Mouginis-Mark, P., Bolton, S., Radebaugh, J., Rathbun, J., Mirino, M., Paris, M., Plainaki, C., Grassi, D., Adriani, A., Sordini, R., Piccioni, G., Sindoni, G., Noschese, R., and Cicchetti, A.: Observations of Io from Juno's close flybys, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7099, https://doi.org/10.5194/egusphere-egu25-7099, 2025.
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 2nd pass mapped latitudes within +/- 45o 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 penetration depth into the sub-surface of the highest frequency channels is on the order of centimeters and the lowest frequency on the order of several 10s of meters. We find the surface of Io generally exhibits specular scattering properties over the 0.6-22 GHz frequency range. We use overlapping observations from the two fly-bys that observe the same areas at different incidence angles and polarizations to solve for the surface dielectric properties. We find the surface dielectric (real part) to be between 2-3, which is consistent with a low-density material. We use the MWR derived real part of the dielectric constant (reflection) with Earth analogs for the imaginary part (loss) to derive the sub-surface temperature profile by inverting the radiative transfer equation. We find the near-surface temperatures decrease with increasing latitude and are coldest at the north pole, consistent with prior infrared observations of the surface skin temperature. We find a strong sub-surface thermal gradient, on the order of 20-40K, over all regions observed by MWR. The sub-surface thermal anomaly is not spatially uniform. We fit several possible models to explain this gradient. One possible explanation are spatially distributed near-surface heat vents topped by a cooled crust, which fit the MWR spectra if they occupy 5-10% of the surface area. We will give an overview of the MWR observations and inferences about the sub-surface thermal and compositional properties.
How to cite: Brown, S., Bolton, S., Levin, S., Ermakov, A., Zhang, Z., Siegler, M., and Adumitroaie, V.: Io’s Sub-surface Heat Distribution Observed by the Juno Microwave Radiometer, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12380, https://doi.org/10.5194/egusphere-egu25-12380, 2025.
Io, one of the most volcanically active bodies in the Solar System, possesses a dynamic atmosphere shaped by volcanic eruptions and the sublimation of surface frost. Utilizing the Submillimeter Array (SMA), we conducted high-resolution observations of Io's atmosphere to investigate its variability and thermal structure. Data collected over three nights in 2022 identified 22 rotational lines of SO₂ within the 336-364 GHz range, allowing for improved constraints on gas temperatures and column densities. Observations indicated that the SO₂ emissions on the dayside were primarily driven by frost sublimation, consistent with previous studies (e.g., Tsang et al. 2012; de Pater et al. 2020), and exhibited equatorial bands and longitudinal asymmetries. The derived gas temperatures ranged from 240 to 270 K, and SO₂ column densities were estimated to be (2-3) × 10¹⁵ cm⁻². Radiative transfer modeling, which incorporated an isothermal profile and gas turbulence —possibly associated with volcanic lava lakes on Io’s surface — provided insights into atmospheric dynamics. This study establishes a robust framework for analyzing Io's atmospheric processes and lays the groundwork for future investigations into its complex interactions with Jupiter's environment.
How to cite: Tseng, W.-L., Hsu, R.-T., Lin, T.-Y., Liu, S.-Y., Gurwell, M., Lai, I.-L., and Liu, H.-Y.: An investigation of Io’s dynamical atmosphere with SMA’s broadband observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4631, https://doi.org/10.5194/egusphere-egu25-4631, 2025.
On September 9, 2022, the Juno spacecraft flew within a few hundred kilometers of Jupiter's moon Europa, and the Microwave Radiometer (MWR) collected passive microwave brightness data over the course of several 30-second rotations of the spacecraft. MWR's 6 channels range from 0.6 GHz to 22 GHz, and receive thermal emission from as deep as several kilometers beneath Europa's icy surface, as well as emission from the galaxy and Jovian synchrotron radiation (JSR) which partially reflects from discontinuities in the ice. The observations span a longitude range from 70˚W to 50˚E and a latitude range from ~20˚S to ~50˚N. The observed microwave brightness temperature in each channel is sensitive to the temperature, opacity, and reflectivity of the ice. The combination of multiple frequencies and varying viewing geometry, along with the angular dependence of the JSR and the known temperature of the surface ice, allow us to place constraints on the reflective properties of the subsurface ice and temperature gradient, which in turn constrains the thickness of the ice shell that covers Europa's subsurface water ocean. In the region observed, we find that the conductive part of Europa’s ice shell, if pure water ice, is greater than 20 km thick, with scatterers predominantly less than a few cm in radius extending hundreds of meters below the surface. We will present our latest results and how we interpret the data.
How to cite: Levin, S., Zhang, Z., Bolton, S., Ermakov, A., Brown, S., Hand, K., Misra, S., Siegler, M., and Stevenson, D.: Juno Microwave Radiometer Observations of Europa's Subsurface Ice , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7108, https://doi.org/10.5194/egusphere-egu25-7108, 2025.
How to cite: Beth, A., Galand, M., Modolo, R., Jia, X., and Leblanc, F.: Ion-neutral chemistry at Ganymede, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8788, https://doi.org/10.5194/egusphere-egu25-8788, 2025.
The Magnetometer investigation’s Advanced Stellar Compass (ASC) onboard Juno provides the first ever in-situ measurements of energetic radiation in the region dominated by the Jovian ring system. The ASC cameras are efficient high energy charged particle detectors, sensitive to energetic electrons (>15MeV) and protons (>120MeV) penetrating the camera’s radiation shielding. A compilation of ASC radiation observations obtained (at 4 samples/s) subsequent to Juno’s arrival at Jupiter thus generated the first detailed map of these particles trapped in Jupiter’s magnetic field. Juno’s orbital evolution, dominated by the southward rotation of its line of apsides by about 1 degree per orbit ensures that practically all regions of Jupiter’s radiation belts are mapped. In the later orbits this drift brought Juno’s orbit to traverse the space near Jupiter connecting along magnetic field lines to the Jovian ring system. The faint, thin ring system of Jupiter occupies the equator between the minor moons Thebe and Methis, and an even fainter toroidal shaped halo inside Methis. The faint rings are predominantly made from micrometer-sized dust and the halo by submicrometer dust, and have resisted precise optical profiling of the rings. Energetic electrons trapped in drift shells meander inwards causing a slow scan of the entire ring region. By mapping the variation in the measured energetic particle flux connecting to the ring region, and comparing these to the undisturbed flux, a detailed profile of the dust rings and the halo is achieved. We present a detained radiation map of the dust ring region, and discuss implications for the density and distribution of ring and halo particulates.
How to cite: Jørgensen, J., Denver, T., Merayo, J., Benn, M., Siegbjørn Jørgensen, P., Connerney, J., and Bolton, S.: Profiling the Jovian ring system, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15006, https://doi.org/10.5194/egusphere-egu25-15006, 2025.
Posters on site: Thu, 1 May, 14:00–15:45 | Hall X4
The Juno spacecraft’s Microwave Radiometer (MWR) detects thermal and non-thermal emissions from Jupiter’s atmosphere and magnetosphere, while complementary instruments observe charged particles and the planet’s magnetic field. Separating the cosmic microwave background, galactic signals, planetary thermal emissions, and synchrotron radiation belts is vital to accurately deriving Jupiter’s atmospheric composition from the MWR’s low-frequency data.
This work presents a refreshed and expanded version of the multi-parameter, multi-zonal synchrotron emission model by Levin et al. (2001), now incorporating in-situ measurements from the MWR. Previously constrained only by pre-Juno Very Large Array (VLA) observations, the underlying empirical electron-energy distribution has been substantially revised to include a time dependence in key model coefficients. We describe the methodologies and challenges involved in this model update, which continues to evolve as new MWR and magnetometer data become available.
How to cite: Adumitroaie, V., Levin, S., and Oyafuso, F. and the Juno MWR Team: Latest Updates on the Modeling of Jupiter's Synchrotron Emissions Using Juno Spacecraft Data , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19801, https://doi.org/10.5194/egusphere-egu25-19801, 2025.
The interchange process is an important mechanism for radial transportation of plasma in the magnetospheres of the gas giants, namely Jupiter and Saturn. During this process, dense and cold flux tubes that move outwards are replaced by returning flux tubes with warm and tenuous plasma. There is an absence of systematical investigation of these returning flux tubes in the Jovian magnetosphere due to limited observations in the past. In this study, we conduct a statistical analysis of the magnetic variation and plasma properties inside the flux tubes inside 20 RJ, based on the observations from MAG and JADE onboard the Juno spacecraft during its first 45 perijove traverses. The results have illustrated that the flux tubes with increased magnetic field account for the majority of the events. There is no significant relationship between the events with increased or decreased magnetic field and magnetic latitude, and both types of events are observed mostly near the equatorial plane. Furthermore, the cross energy of returning flux tubes with decreased low-energy electron flux and increased high-energy electron flux is around several keV, depending on the type of magnetic field variation. These results provide great insight into the mass and magnetic flux transportation in the inner Jovian magnetosphere.
How to cite: Yue, C.: A Statistical Analysis of the Returning Flux Tubes in the Jovian Magnetosphere Based on Juno Observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-179, https://doi.org/10.5194/egusphere-egu25-179, 2025.
Ion cyclotron waves (ICWs) have shown to be a valuable tool to identify pick-up ion species around planets and moons, when plasma instruments are not sufficiently available. We investigate the high-resolution (3 Hz) Galileo magnetometer data for the presence of ICWs of various sulfur-bearing species and other elements heavier than oxygen (this because the IC frequency should be below the Nyquist frequency of 1.5 Hz). We find evidence for SOx (x = 0 – 3), Cl, K and H2S, however, the deduced pick-up densities vary strongly along the different flybys. Using the deduced pick-up densities for each flyby and a model for the neutral gas escaping Io, which gets ionized, we can obtain an estimate for the total mass loss of this volcanic moon.
How to cite: Volwerk, M., Schmid, D., Kivelson, M., Khurana, K., Jia, X., Lammer, H., Simon Wedlund, C., Bagenal, F., Dols, V., Nakamura, R., Krupp, N., and Roussos, E.: Ion Pick-up around Io in the Galileo Era, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1582, https://doi.org/10.5194/egusphere-egu25-1582, 2025.
Jupiter was the first planet other than Earth, where lightning discharges were detected using the radio wave measurements of the Voyager spacecraft in 1979. Starting with Voyager 1, all spacecraft missions to Jupiter detected lightning as bright spots in the optical images of the nightside of the planet. The Juno spacecraft currently orbits Jupiter and its measurements in the audible frequency range below 20 kHz often show rapid whistlers, electromagnetic signatures of electrical discharges with very low dispersion. These measurements represent the largest known database of lightning detections at this planet.
We explore the Juno measurements of rapid whistlers in order to estimate their amplitudes which, in turn, can help us to estimate the energy radiated in this part of the electromagnetic spectrum from the Jovian lightning discharges. We use a newly developed method based on the search for sufficiently large coherent structures in the spectrograms of rapid whistlers. The choice of the parameters of this method is supported by extensive modeling to ensure that the probability of false positive detections is reasonably low. Another set of simulations is performed for different backgrounds to estimate the minimum detectable amplitude of the rapid whistlers.
In total, our analysis includes 1357 rapid whistlers from the first 8 perijoves, and we take into account a geometrical correction based on changing attitude of the spacecraft and its varying distance from the top of the ionosphere (300-km altitude above the 1-bar level). After performing these normalizations, we estimate the energy which was radiated from the source lightning discharges into the rapid whistlers. We obtain a wide distribution of values with a range of 308–3341 J between the lower and upper quartiles, and with the median value of 973 J. These energies are similar to energies of electromagnetic waves radiated at audible frequencies from the terrestrial lightning discharges. Our result differs from most of the previous estimates of lightning energies at Jupiter, which found them much larger than at Earth. However, our results are consistent with the latest optical measurements onboard Juno.
How to cite: Rosicka, K., Santolík, O., Kolmašová, I., Imai, M., and Kurth, W.: Estimation of the energy of Jovian lightning discharges based on the analysis of rapid whistlers detected by Juno, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3631, https://doi.org/10.5194/egusphere-egu25-3631, 2025.
Whistler mode chorus waves are commonly observed in planetary magnetospheres and play an important role in the acceleration and loss of planetary energetic electrons. By combining the observations from Galileo and Juno, we conduct a detailed statistical analysis of the spatial distribution of the occurrence rates and averaged amplitudes of chorus waves in the Jovian magnetosphere. The statistical results show that chorus waves are widely distributed at 5 < M-shell < 15 within the magnetic latitudes (MLats) of < 50°, with the averaged amplitudes ranging from 3 pT to ~ 50 pT. The most intense waves are found in the duskside inner magnetosphere at 8 < M-shell < 11 near the equatorial region (MLat < 20°). The wave amplitudes decrease significantly with increasing magnetic latitude, and are an order of magnitude larger on the duskside compared to the dawnside. Based on the statistical results, we develop an empirical model of the distribution of chorus wave amplitudes as a function of M-shell, magnetic local time and magnetic latitude, which can provide key information of the waves for future studies of resonant wave-particle interactions between chorus waves and energetic electrons at Jupiter.
How to cite: Lu, P., Cao, X., Ni, B., Wang, S., and Long, M.: Statistical distribution of chorus waves in Jupiter’s magnetosphere based on Galileo and Juno observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5343, https://doi.org/10.5194/egusphere-egu25-5343, 2025.
Juno has transformed our view of Jupiter through major discoveries about its interior structure, origin, and evolution; atmospheric dynamics and composition; magnetic dynamo; and polar magnetosphere. The natural evolution of Juno’s polar orbit brings new regions within reach with every close passage to Jupiter, as the inbound equator crossing marches ever closer to the giant planet. The 1st extended mission began in August 2021 and provided the first close flybys of Io, Europa and Ganymede since the Galileo mission. The second extended mission (EM2) begins in October 2025 providing opportunities for Juno to probe previously unexplored regions, and to follow up on Juno’s discoveries made during its prime and 1st extended missions. The Juno spacecraft and instruments are in excellent health. During EM2, Juno will dive deep within Jupiter's inner radiation belts where the rings and inner moons reside. EM2 provides an opportunity for a thorough investigation of these components and their complex interaction, providing a unique data set to compare with other giant planet ring systems, including the ice giants. The migration of the periapsis northward creates an opportunity to explore in-situ Jupiter's ring-moon system, investigate Jupiter’s northern hemisphere and the unexplored regions of Jupiter's distant southern magnetospheric boundaries. During EM2, Juno’s polar perijoves will provide the opportunity to continue the exploration of Jupiter’s circumpolar cyclones over a wide range of altitudes/depths via imagery, occultations and microwave sounding. Radio science occultations will icharacterize the upper atmosphere to levels as deep as 0.5 bar. EM2 gravity passes over the north polar region will constrain the depth and mass of the polar cyclones and will also be compared to MWR's sounding of the same. Juno’s 2nd extended mission proposal is currently being reviewed. An overview of the new opportunities provided with EM2 will be presented.
How to cite: Bolton, S. and the Juno Science Team: Juno's 2nd Extended Mission, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5184, https://doi.org/10.5194/egusphere-egu25-5184, 2025.
Thermochemical models of Jupiter's troposphere predict liquid water clouds below the 4–5 bar level [1,2], with NH4SH and NH3 aerosols forming higher layers. Consequently, spectroscopic detection of deeper water clouds remains sparse [3,4]. This study examines cloud-clearance areas identified using JIRAM-Juno spectra near the Great Red Spot and the South Equatorial Belt, along with their implications for the planet's cloud structure.
We analyzed spectra from Juno’s first perijove in August 2016. JIRAM covers 2–5 μm with 13 nm resolution, capturing data along 256-pixel slits. The limited data volume and operational constraints often restrict spatial coverage. For λ > 4 μm, thermal emission dominates, with lower 5-μm signals corresponding to NH4SH and NH3 opaque cloud tops at 1–0.5 bars. Cloud-clearance regions appear brighter, revealing deeper levels at 4–5 bars, where absorption from H2 (collision-induced) and other minor gases (NH3, H2O, PH3, GeH4) prevails. At λ < 3.2 μm, reflected solar radiation dominates, while vertical aerosol profiles and gas opacity—notably methane—shape the signal. A radiance maximum at 2.78 μm highlights transparent regions in methane and ammonia spectra, allowing detection of clouds down to 2–3 bars in the absence of upper aerosol layers.
JIRAM data confirm an anticorrelation between thermal (≥ 5 μm) and solar (2.73 μm) signals [5], consistent with a gray upper cloud deck. Among these trends, regions with high thermal flux but very low solar signals suggest an exceptionally thin upper cloud deck. Their locations align with deep-cloud structures previously described in [6] in the wake of the Great Red Spot.
We compared spectral properties of these clearance areas to neighboring regions of similar thermal intensity but higher solar signals. A notable feature in clearance areas is a broad peak at 4.55 μm in the spectral ratio, inconsistent with deep clouds. This peak indeed suggests an absence of opacity sources at the 3–4 bar level (where 4.55-μm contribution functions peak [7]). Furthermore, preliminary simulations assuming liquid water clouds at 3–8 bars (following [4]) for non-clearance regions show a spectral ratio peak at 4.7 μm, not 4.55 μm. Raising the water clouds to 1.5 bars yields similar results. Although further exploration of cloud altitude, density, particle composition (liquid/ice), and size distribution is required to rule out the occurrence of deep water clouds, a set of spectral retrievals suggests that the spectral properties of clearance areas are better explained by local depletions in phosphine content and exceptionally thin clouds at the 1-bar level.
JIRAM is supported by the Italian Space Agency (ASI). This work is funded by the Addendum n. 2016-23-H.3-2023 to the ASI–INAF Agreement n. 2016-23-H.0.
[1] Rensen F. et al. (2023) Remote Sens., 15(3), 841; [2] Atreya S. K. et al. (1999) Planet. & Space Sci., 47(10-11), 1243. [3] Simon-Miller, A. A. et al. (2000) Icarus 145, 454–461. [4] Bjoraker, G. L. et al. (2015) ApJ, 810(2). [5] Irwin, P.G.J. et al. (2001) Icarus, 149, 397–415. [6] Banfeld, D. P. J. et al. (1998) Icarus, 135, 230–250. [7] Sromovsky, L.A. and Fry, P.M. (2018) Icarus, 307, 347–370.
How to cite: Grassi, D., Biagiotti, F., Mura, A., Piccioni, G., Plainaki, C., Sindoni, G., and Bolton, S. J.: Spectral properties of cloud clearance regions in the wake of Jupiter’s Great Red Spot from JIRAM-Juno data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4098, https://doi.org/10.5194/egusphere-egu25-4098, 2025.
Understanding the dynamics of planetary magnetospheres and auroral phenomena hinges significantly on magnetic reconnection. The rapid rotation of Jupiter and Saturn and the internal mass sources in the inner magnetospheres give rise to the magnetodisk current sheet that encircles the planet. The magnetodisk current sheet provides a place that is conducive to reconnection. Notably, the magnetodisk reconnection process is not confined to the nightside magnetosphere. The reconnection sites occur at various local times throughout the magnetosphere and rotate with the magnetosphere. The discretely distributed small-scale magnetodisk reconnection sites can lead to a comprehensive release of energy and mass from the magnetosphere.
How to cite: Guo, R. and Yao, Z.: Magnetodisk Magnetic reconnection in the centrifugally dominated giant planets, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6572, https://doi.org/10.5194/egusphere-egu25-6572, 2025.
Jupiter’s ultraviolet (UV) polar auroral emissions are highly variable, both spatially and temporally. Observations over Jupiter’s northern and southern polar aurora during Juno’s prime mission did not reveal electron distributions with sufficient energy flux to produce the range of UV brightnesses (10s to 100s of kilorayleigh; kR) typically observed in that region. One suggestion was that significant electron acceleration was occurring below the altitudes sampled by Juno during that timeframe. Juno’s extended mission has provided an opportunity to test this hypothesis by accessing altitudes below 0.2 jovian radii (1 RJ = 71,492 km) above Jupiter’s northern polar auroral region. We present the characteristic features and energy flux of electron distributions at these low altitudes, primarily between 30 eV to 30 keV. A persistent feature below altitudes of 0.5 Rj is a low-energy cut-off in the electron distributions at a few 100s of eV. The energy flux in this energy range have maximum values of several 10s of mW/m-2, suggesting that contributions from electrons above 30 keV are likely required to account for the UV polar auroral emissions.
How to cite: Ebert, R., Clark, G., Elliott, S., Allegrini, F., Bagenal, F., Bolton, S., Connerney, J., Szalay, J., Valek, P., and Wilson, R.: Characteristic Properties of 30 eV to 30 keV Electrons at Low-Altitude Over Jupiter’s Northern Polar Aurora, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7322, https://doi.org/10.5194/egusphere-egu25-7322, 2025.
Decametric radio emissions (DAM) originating in Jupiter’s polar aurorae ought to generate along magnetic field lines at the local electron gyrofrequency. The Io-related DAM have received particular attention since the 1980’s, and it is expected that the maximum frequency of these emissions is bounded by the maximum magnetic field strength near the footprint of the instantaneous Io Flux Tube. DAM have been observed from Earth and spacecraft flybys before Juno, limiting the observation geometry to equatorial latitudes. Since 2016, and thanks to Juno, we have been able to observe Io-related DAM from a wide range of latitudes, leading to the observation of a new DAM feature that we preliminarily called “butterfly”. We analyze the Waves data from May 2016 to June 2023 searching for these butterflies to catalog them and determine their relationship with Io and the Jovian magnetic field. Based on the observation geometries, we found that these events (˜ 135) are Io-related, they are always observed when Juno is in southern latitudes, they last for ˜5 hours and their maximum observed frequency is ˜20 MHz. As Juno is spending more time in southern latitudes as the mission progresses, the observation of butterflies keeps increasing over the years. Here, we study the role of the dipolar magnetic field of the southern hemisphere of Jupiter in the generation and observation of the butterfly events.
How to cite: Martos, Y. M., Connerney, J. E. P., Kurth, W., Imai, M., and Kotsiaros, S.: Jupiter’s magnetic field geometry and its relation with new decameterradiation events observed by Juno, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7359, https://doi.org/10.5194/egusphere-egu25-7359, 2025.
Since the discovery of Jupiter’s auroral footprints linked to the Galilean moons - Io, Europa, Ganymede, and Callisto - extensive efforts have been made to unravel the mechanisms behind these unique phenomena, which have no equivalent on Earth. The Juno mission has been fundamental in this effort, providing unprecedented access to Jupiter's polar regions, significantly enhancing our understanding of the satellite footprints and Jovian aurorae. Juno’s observations have revealed exceptional detail, enabling a more thorough characterization of the morphology of the footprints and the electrodynamic processes that drive their formation.
In this study, we aim to investigate these features from a new perspective by examining their spectral signature, a dimension largely unexplored until now, with a focus on the H3+ emissions in the infrared. This is accomplished by combining the L-band images and spectra acquired from orbit PJ 1 to 40 by the Jovian InfraRed Auroral Mapper (JIRAM), onboard of the Juno spacecraft. The images provide the spatial context necessary to identify the spectra sampling Io-, Europa- and Ganymede-induced aurorae, the primary targets of this work. These spectra are then used to derive the temperature and column density of H3+ within the various structures forming the footprints, including the Main Alfvén Wing (MAW), the Transhemispheric Electron Beam (TEB), the Reflected Alfvén Wing (RAW). Additionally, we compare the derived values with those of the main aurora, as reported in earlier JIRAM spectral studies, to gain a deeper understanding of the similarities and differences between the footprints and the main emission.
Through this analysis, our objective is to provide further insights to the existing body of knowledge on Jovian auroral footprints and on the complex interactions among Jupiter's magnetosphere, ionosphere, and its moons.
How to cite: Castagnoli, C., Moirano, A., Mura, A., Adriani, A., Altieri, F., Dinelli, B. M., Migliorini, A., Noschese, R., Sordini, R., and Tosi, F.: Probing H3+ emission spectra in the footprints of Galilean moons with JIRAM, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9433, https://doi.org/10.5194/egusphere-egu25-9433, 2025.
A zonal flow pattern is well-established for Jupiter's lower latitudes. At high latitudes, this patterm breaks down as observed in visible-light, infrared, and much of the radio-wave spectrum. But around each pole, Juno's instruments observe a cluster of circumpolar cyclones (CPC) that appears to remain essentially stable over at least six years. A heavily simplified multilayer fluid dynamical model suggests that such a pattern may be able to form in overlying atmospheric layers from an underlying zonal flow pattern.
Juno's wide-angle visible-light imager, JunoCam, continues to observe Jupiter's north polar region on a regular basis during each perijove flyby. As it is now northern summer on Jupiter, JunoCam with its wide field of view can see a little more than half of the northern CPCs. While locally the CPCs can change substantially, the overall octagonal pattern remains mostly stable.
An attempt to model such a CPC pattern with an incompressible 2D Euler flow numerical model can maintain such a pattern temporarily. But it shows several caveats in detail. Several questions remain: Why is the northern CPC pattern octagonal? Why is it stable? How did it form? Why are there counter-rotating cores in some of the CPCs? Why are many of the CPCs of an almost circular shape? Why are there two distinct morphologies, i.e., filled and spiral?
Friction with an underlying steady flow can modify a 2D Euler flow in such a way that anticyclonic vorticity can form inside a cyclone. But explaing the CPC pattern itself appears hard with such a two-layer model. However, the approach can be generalized in a computationally feasible way: Couple the 2D Euler flow tightly enough to the underlying steady flow such that it converges to a steady flow itself, and start with this new steady flow iteratively the same way. In this way, only one 2D fluid layer requires to be simulated at a time, but still an arbitrary number of layers can be simulated.
This approach turns out to morph an axially symmetrical steady zonal flow with only small fluctuations into a CPC pattern when traversing the layers from bottom to top. Since each layer becomes essentially a steady flow, the CPC pattern ends up stable for any given modelled fluid layer of interest. We can think of portions of the time axis being translated into the vertical z-axis. It is those portions that change the flow pattern. A more chaotic flow can be achieved by reducing the coupling between layers.
The simplification to the one-way effect of the coupling between layers is assumed to be justified by the density gradient.
How to cite: Eichstädt, G., Brueshaber, S., Li, C., Orton, G., Rogers, J., Hansen-Koharcheck, C., and Bolton, S.: Deriving circumpolar cyclones from zonal flow with a simplified multi-layer fluid model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7436, https://doi.org/10.5194/egusphere-egu25-7436, 2025.
NASA’s Juno mission has been orbiting Jupiter since 2016, aiming to unveil the planet’s origin and evolutionary history. Equipped with a suite of advanced remote sensing instruments, the spacecraft has delivered groundbreaking insights into Jupiter’s atmosphere, magnetic field, and internal structure, enabled by its highly elliptical orbit. In 2021, after completing 35 perijoves, Juno’s prime mission ended, transitioning into its extended mission phase. This extended phase is characterized by altered trajectories, driven by perturbations from Jupiter’s complex gravity field. These new trajectories have provided invaluable opportunities for close approaches to the Galilean satellites, including Io, the most volcanically active body in the Solar System.
The prevailing understanding of Io's intense volcanic activity attributes it to the energy generated by tidal deformations resulting from variations in its distance from Jupiter during its orbit. This energy may lead to varying degrees of interior melting, which in turn determines whether Io's subsurface hosts a global magma ocean. The presence and depth of such a melted subsurface layer significantly influences the dynamic behavior of Io’s crust. Notably, this manifests as diurnal librations, whose amplitude depends on whether a magma ocean is present. However, the phenomenon of longitudinal librations of Io’s surface has yet to be observed directly. Two of the most recent flybys of Juno, I57 and I58, that occurred on December 30, 2023, and February 3, 2024 enabled the acquisition of high-resolution images of the moon using the JunoCam camera. From an altitude of approximately 1500 km, these JunoCam data products contain valuable data to estimate or provide an upper bound for the amplitude of the longitudinal libration of Io.
Incorporating optical observables generated from landmarks and surface features with traditional radiometric measurements can enhance orbit determination procedures and enable the estimation of an upper bound for Io’s diurnal libration, contributing to a more comprehensive understanding of Io's interior structure and evolution. In this work, we focus on the analysis of JunoCam images to obtain the coordinates of notable surface features and the target’s centroid in the camera frame. The uncertainty in the estimation of these and other parameters depends on the number of available features and images, as well as the accuracy of the registration methodology employed. While the high resolution of JunoCam images acquired during the flybys may not be sufficient to clearly determine Io's libration amplitude, we aim to establish a reliable constraint on the models describing the libration of Io.
How to cite: Togni, A., Gomez Casajus, L., Zannoni, M., and Tortora, P.: Assessing Io's Libration Using JunoCam Acquisitions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13503, https://doi.org/10.5194/egusphere-egu25-13503, 2025.
Low intensity phenomena on Jupiter in the visual range, e.g. aurora and lightning, are readily visible on the nightside of the gas giant. The highly elliptic orbit of NASA’ Jupiter probe, Juno, provide perijove distances in the range of 5-10,000km, offering unique close range observation opportunities, when the probes optical instruments happens to be pointed towards dark regions of the planet.
The micro Advanced Stellar Compass (µASC), an instrument onboard Juno primary purpose is to serve as an attitude reference for the Juno Magnetic Field investigation, provides accurate bias free attitude information continuously throughout the prime mission. The µASC uses a set of four optical sensors that are optimized for low-light imaging, which enables detection of stars and objects as faint as 7-8Mv.
The 13° angular offset between the star tracker cameras’ axis and Juno’s spin axis (in anti-sun direction), routinely places the Jovian night-side high latitude regions into the field of regard of the star trackers. This peculiar geometry facilitates imaging of the low light phenomena, such as lightning and aurora, at large slant angle offering unique altitude information of the upper atmosphere phenomena imaging as well as its localization. The star tracker images further offer star occultation observation enabling profiling the density profile of the upper atmosphere.
We revisit captured ASC image data, extracting observations of lightning events and attitude determinations, to estimate the lightning altitude in the Jovian atmosphere. The altitude at which lightning occurs in Jupiter’s atmosphere is key to an ammonia-water dynamical system that is thought to explain the puzzling depletion of ammonia observed by the Microwave Radiometer investigation.
How to cite: Benn, M., Jørgensen, J. L., Jørgensen, P. S., Denver, T., and Connerney, J. E.: Low-light Lightning Detections in the Jovian Atmosphere by Juno’s Advanced Stellar Compass, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17163, https://doi.org/10.5194/egusphere-egu25-17163, 2025.
The Juno spacecraft has been orbiting Jupiter since 2016. The evolution of Juno's orbit allows the later orbits to provide unprecedented insights into the inner regions of the Jovian environment. 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.
Jupiter’s moon Io orbits at a distance of approximately 5.9 Jupiter radii. Due to its intense volcanic activity, Io ejects large amounts of ionized gases and dust into space, which form a dense, donut-shaped plasma region around Jupiter known as the Io torus, located along Io’s orbit. Jupiter’s strong magnetic field traps highly energetic radiation environment with the most intense region near Io.
Since its arrival at Jupiter, Juno has completed numerous orbits, traversing multiple longitudinal regions of the Jovian system and with the orbit evolution drift of the line of apsides south, effectively scanning the entire Jovian radiation belts. Specifically, the ASC has consistently recorded variations in radiation levels when Juno crosses magnetic field lines connected to the Io torus, which interacts with it. These systematic variations provide valuable data for understanding the structure and dynamics of this unique plasma environment.
We present a detailed map of the locations where these radiation variations are observed, enabling us to quantify the geometry and spatial distribution of the Io torus relative to Jupiter’s magnetic field. Additionally, we explore possible physical mechanisms driving these observed variations, such as the acceleration and trapping of particles within the torus or their interactions with Io’s volcanic emissions and Jupiter’s magnetospheric processes.
How to cite: Merayo, J. M. G., Jørgensen, J. L., Denver, T., Benn, M., Jørgensen, P. S., Connerney, J., and Bolton, S.: The Io torus as observed by the Juno ASC, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19287, https://doi.org/10.5194/egusphere-egu25-19287, 2025.
Posters virtual: Thu, 1 May, 14:00–15:45 | vPoster spot 3
EGU25-3870 | Posters virtual | VPS27
Juno Observations of Io's Alfvén Wing from 23 Io RadiiThu, 01 May, 14:00–15:45 (CEST) | vP3.7
On 13 June, day 165 of 2024, Juno passed through Io's main Alfvén wing at a distance of some 23 Io radii (RI) below the moon during perijove (PJ) 62. Evidence for this passage was clearly seen in the Juno plasma wave, magnetometer, and ion plasma data. The plasma wave signature was an intensification of quasi-electrostatic waves below about 1 kHz with a weaker magnetic component, all lasting for about 90 seconds. A strong modification of the magnetic field was observed primarily in the co-rotation direction but with a significant component in the direction away from Jupiter. Ions in the range below about 1 keV/q were slowed within the Alfvén wing. The Juno mission has afforded multiple opportunities to examine the Io-Jupiter interaction near the planet and two close flybys through the Alfvén wing during perijoves 57 and 58. Hence, PJ62 provided observations of the Io-magnetosphere interaction at an intermediate distance. The broadband electromagnetic emission below 1 kHz was observed during PJs 57 and 58, however, the magnetic component is markedly reduced from those. An estimate of the power in the interaction obtained by scaling the Poynting flux and integrating over the cross section of the flux tube is ~500x109 W. And modeling of the current suggests filamentation of the Alfvén waves as observed in other Io Alfvén wings.
How to cite: Kurth, W., Sulaiman, A. H., Connerney, J. E. P., Allegrini, F., Valek, P., Ebert, R. W., Paranicas, C., Clark, G., Kruegler, N., Hospodarsky, G. B., Piker, C. W., Kotsiaros, S., Imai, M., and Bolton, S. J.: Juno Observations of Io's Alfvén Wing from 23 Io Radii , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3870, https://doi.org/10.5194/egusphere-egu25-3870, 2025.
EGU25-14033 | ECS | Posters virtual | VPS27
Ion Parameters Dataset from Juno/JADE Observations and Its ApplicationsThu, 01 May, 14:00–15:45 (CEST) | vP3.9
After its arrival at Jupiter in July 2016, Juno conducted a global survey of Jupiter's magnetosphere with its highly eccentric polar orbit. Since then, the JADE instrument has accumulated a large amount of plasma measurements. Using a developed forward modeling method and a supercomputer cluster, we fit all ion measurements between 10 and 50 RJ from PJ5 to PJ56, obtaining a dataset with 70,487 good fits that consists of the following set of plasma parameters: abundances of different heavy ions, density, temperature, and 3‐D bulk flow velocity of heavy ions. This dataset has applications in the research on large-scale structures and small-scale dynamics in Jupiter’s magnetosphere, particularly the equatorial plasma disk region. Potential applications of this dataset include, but are not limited to, the following topics: 1) How is plasma distributed radially and vertically within the plasma disk? 2) What drives the local time asymmetry of plasma flow? 3) What are the consequences of centrifugal instabilities? 4) How is mass and energy transported in the magnetosphere? 4) How is force balance achieved and maintained? An overview of the dataset and some example applications will be presented in this talk.
How to cite: Wang, J., Bagenal, F., Wilson, R., Valek, P., Ebert, R., and Allegrini, F.: Ion Parameters Dataset from Juno/JADE Observations and Its Applications, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14033, https://doi.org/10.5194/egusphere-egu25-14033, 2025.
EGU25-15614 | Posters virtual | VPS27
Impact of self-shadowing on the Jovian Circumplanetary disk ice compositionThu, 01 May, 14:00–15:45 (CEST) | vP3.10
Modeling the formation conditions of the Galilean moons remains a significant challenge. While it is widely assumed that the moons formed within a circumplanetary disk (CPD) that surrounded Jupiter during the final stages of its growth, the physical properties and composition of this disk remain poorly constrained in theoretical models.
One approach to infer the properties and composition of the CPD is to use the bulk composition of the Galilean moons as a reference to extract compositional trends for the disk. A notable example is the gradient in water content with distance from Jupiter: from completely dry Io to a 1:1 water to rock ratio on Ganymede and Callisto. This gradient strongly suggests that the CPD exhibited a corresponding water abundance gradient during its formation.
With the JUICE and Europa Clipper missions currently cruising to the Jovian system, the coming decade will provide an unprecedented opportunity to study Europa, Ganymede, and Callisto. These missions are expected to refine our understanding of the bulk composition of the moons and provide new constraints for CPD models.
In this context, we aim to model the midplane volatile species composition of the CPD using a 2-dimensional proprietary framework. The model assumes a quasi-stationary disk heated by viscous stress, infalling gas, and the young, hot Jupiter. A key feature of the model is the presence of shadow regions that can be up to 100 K cooler than their surroundings and persist for up to 100 kyr.
Our results indicate that the profile of volatile species in the midplane shows enrichment peaks during the early evolution of the disk. However, maintaining these enrichments requires an accretion rate to the CPD of about 10-7 Mjup/yr for at least 1 Myr. If the accretion rate decreases too rapidly, the ice abundances rapidly decrease.
In addition, we show that shadows within the CPD can significantly influence its volatile composition on short timescales of less than 100 kyr. These shadowed regions may trap ice of volatile species that would otherwise remain in the vapor phase, thereby altering the overall composition of the CPD.
How to cite: Schneeberger, A., Bennacer, Y., and Mousis, O.: Impact of self-shadowing on the Jovian Circumplanetary disk ice composition, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15614, https://doi.org/10.5194/egusphere-egu25-15614, 2025.
