Hisaki is an earth orbiting extreme ultraviolet spectroscope dedicated for observing solar system planets. Thanks to its monitoring capability, Hisaki has carried out unprecedented continuous observation of Io plasma torus, Jovian aurora, and Mars and Venus upper atmosphere since December 2013. One of notable phenomena observed by Hisaki is significant enhancements of neutral gas (sodium and oxygen) from Io occurred in the spring of 2015. Hisaki revealed that not only the plasma source, but transport, heating, and loss processes of magnetospheric plasma were influenced by the variation in the neutral source input. The presentation will include related topics from recent Hisaki publication. Since the autumn of 2016, the Juno spacecraft was in the orbit around Jupiter. Hisaki monitored activities of Jovian aurora and the plasma torus in the Juno era. These datasets will provide opportunities to compare in-situ observation by Juno with the global view by Hisaki. 
JAXA approved the Hisaki mission period by the end of March 2023. As a future remote observation platform, we are going to propose a UV space telescope, LAPYUTA (Life-environmentology, Astronomy, and PlanetarY Ultraviolet Telescope Assembly), a Japanese-leading mission using heritages of UV instruments for planetary science (e.g., Hisaki) and space telescope techniques for astronomy. One of goals of this mission is dynamics of our solar system planets and moons as the most quantifiable archetypes of extraterrestrial habitable environments in the universe. Water plume that gushes from the subsurface ocean of Galilean moons and tenuous atmosphere which is generated by bombardment of energetic charged particles to the surface are primary targets of LAPYUTA. As the plume activity and the atmosphere are not stable, continuous monitoring with high spatial resolution is essential. The icy moon's plume and ambient space will be deeply explored with the spacecraft by NASA's and ESA's icy moon missions in 2020s-2030s. The complementary remote sensing by LAPYUTA will visualize their global structure and temporal dynamics.

How to cite: Tsuchiya, F., Kasaba, Y., Yoshikawa, I., Murakami, G., Yamazaki, A., Yoshioka, K., Kimura, T., Tao, C., Koga, R., Kita, H., Masunaga, K., Kagitani, M., Sakai, S., and Kuwabara, M.: Major results from the Hisaki mission and future perspectives, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4751, https://doi.org/10.5194/egusphere-egu23-4751, 2023.

The Juno Waves instrument often detects brief, band-limited emissions when the spacecraft crosses magnetic fields threading Io’s M-shell, or vicinity thereof, up to about 30 degrees magnetic latitude. The disturbances have durations of order one minute and are observed below the electron cyclotron frequency. While plasma densities are often not available, it is thought that the frequency of the events are below the plasma frequency of the surrounding medium. Often, the first electron cyclotron half-harmonic is weakened or disrupted at the time of the events. While the events can be seen in isolation, there are typically a few of them with temporal spacing between about 15 to 40 minutes. Similar features were commonly seen by the Cassini radio and plasma wave instrument at Saturn and were identified as ’fresh’ injections or evidence of inward-moving flux tubes due to the centrifugal interchange instability. As such, they were characterized as having depleted thermal plasma and enhanced energetic plasma with electron distributions unstable to wave modes such as the upper hybrid band and chorus. Such events were also observed by Galileo. As fresh injections, the energetic particles associated with them have not had time to drift in longitude due to gradient and curvature drift forces.

How to cite: Kurth, W., Hospodarsky, G., Sulaiman, A., Mauk, B., Clark, G., Allegrini, F., Connerney, J., and Bolton, S.: Evidence of Fresh Injections Related to the Interchange Instability in the Io Torus, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4260, https://doi.org/10.5194/egusphere-egu23-4260, 2023.

Europa, the smallest of the Galilean moons, is embedded within Jupiter’s magnetosphere where a rapidly flowing plasma interacts electromagnetically with the moon’s atmosphere and its surface. The magnetic field in the plasma is also affected by Europa’s induced magnetic field in a subsurface conducting layer. On September 29^th, 2022 the Juno spacecraft flew by the vicinity of Europa at a distance of ~350 km, and it provided the first in-situ observations since Galileo’s last pass on January 3^rd, 2000.

In this work, we model the large scale interaction of Jupiter’s magnetospheric plasma with Europa and its atmosphere for the conditions of the Juno flyby. We apply the single fluid MHD PLUTO code based on Mignone et al., [2007], and also employed by Duling et al. [2022] to describe Ganymede’s plasma interaction. Our model accounts for ion-neutral collisions, electron impact ionization, dissociative recombination, and electromagnetic induction in a subsurface water ocean. In particular, we prescribe Europa’s O₂ atmosphere with a number of analytical models in which we consider several degrees of asymmetry. Furthermore, we include a tracer description in the model and solve advection equations for the production of the water-group pickup ions H⁺ and H₂⁺. The simulation results are compared with in-situ measurements provided by the magnetometer and the JADE instrument onboard the Juno spacecraft. Our study is used to further constrain properties of the moon’s atmosphere and to quantify the effects of their variability on the plasma interaction.

How to cite: Cervantes Villa, J. S., Saur, J., Szalay, J., and Connerney, J.: MHD simulations of Europa’s interaction with the jovian magnetosphere: insights from the Juno flyby, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1511, https://doi.org/10.5194/egusphere-egu23-1511, 2023.

Since Juno’s orbit insertion, the attitude reference for the MAG investigation onboard Juno, the micro Advanced Stellar Compass (µASC), and as a part of its additional functionality, continuously measures high energy electron fluxes in Jupiter’s magnetosphere. The µASC camera head unit (CHU) sensitivity to electrons with kinetic energy greater than 15 MeV and protons with energies >80MeV, provides a means of in-situ mapping of electron fluxes sampled during 47 Juno orbits.

The focus of this study are events observed when Juno is traversing M-shell of the Galilean moon, Europa, which shows distinctly different signature from that the other moons.

We present µASC observations of energetic electrons interaction with Europa moon. Europa generates a wake, that affect the high energy electron driftshell, by scattering electrons into the loss-cone. The wake is then dissolved and these interactions are observed around 20° down tail. On the upstream side, the energetic drift shell is free from hard radiation as Europa acts as an obstacle for the energetic electrons. This assymetry result in a lower electon density on the upstream side resulting in an E-field filling in the e^- population from surrounding driftshells in less than 10°.

How to cite: Herceg, M., Jørgensen, J. L., Denver, T., Sushkova, J., Jørgensen, P. S., Connerney, J. E. P., and Bolton, S. J.: µASC observations of Jovian energetic electrons interaction with Europa moon, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11468, https://doi.org/10.5194/egusphere-egu23-11468, 2023.

Jupiter hosts very intense auroral emissions, which originates from various magnetospheric processes. One of these emissions is associated with the orbital motion of the innermost Galilean satellite Io, which orbits at ~5.9 R_J from Jupiter’s centre (1 R_J = 71492km). At that distance, the magnetospheric plasma is forced to corotation by the strong planetary magnetic field. Therefore Io, which orbits at a slower speed than the corotating plasma, is continuously swept by both the plasma and the Jovian magnetic field. The relative velocity between Io and the plasma triggers a perturbation that propagates along the magnetic field lines and towards the ionosphere as Alfvén waves. Along their way, the Alfvén waves can accelerate electrons into the planetary atmosphere, where they ultimately generate an auroral emission called the Io footprint. The position of the Io footprint depends on the speed of the Alfvén waves, which in turn depends on the magnetic field geometry and magnitude as well as on the plasma mass distribution around Io, whose sulfur-dioxide-rich atmosphere constantly supply a dense cloud of plasma around Jupiter, called the Io Plasma Torus.

In 2016, Juno reached the Jupiter system and, since then, the Jovian InfraRed Auroral Mapper (JIRAM) has been observing the infrared emission associated with the Io footprint with a spatial resolution of ~ few tens of km/pixel. Thanks to the high resolutions of JIRAM, we report evidences of variability in the Io footprint position that are not related to the System III (i.e: the frame corotating with Jupiter) longitude of Io. Using a model for the plasma distribution of the Io Plasma Torus and the magnetic field, we quantitatively determine the state of the plasma distribution corresponding the JIRAM observations. This is the first attempt to retrieve quantitative information on the torus variability by using the Io footprint position. The best-fit plasma density and temperature are consistent with previous observations and analysis of the Io Plasma Torus from the Voyager 1, Voyager 2, Cassini, Galileo and Hisaki spacecrafts. Besides, we found that both density and temperature can exhibit remarkable non-System III variability, which can be ascribed either to local time asymmetry of the plasma in the Io torus or to temporal variation in the torus mass loading.

How to cite: Moirano, A., Mura, A., Bonfond, B., Connerney, J., Dols, V., Denis, G., Hue, V., and Gérard, J.-C. and the JIRAM team (INAF-IAPS, CNR-ISAC, ASI; Italy): Modelling the Io Plasma Torus and Application to the Variability of the Io Footprint Position observed by Juno-JIRAM, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5820, https://doi.org/10.5194/egusphere-egu23-5820, 2023.

Nasa’s JUNO spacecraft, now in its extended mission, is finally passing through the Io plasma torus (IPT) taking in situ measurements of the plasma environment using the JUNO-JADE instrument. Through September of 2025 we will have almost 40 passes through the IPT of JUNO observations. Further, there is recent evidence from ground based optical telescopes that Io recently had a major eruption increasing neutral emission close to Io around Thanksgiving of 2022 (C. Schmidt, personal communication, 2022). We have been developing a nominal torus model based on in situ plasma measurements from previous missions, emission modeling of UV spectra, and ground based optical emission derived plasma parameters. Physical chemistry modeling informs our model and is another point of comparison. We use Phipps & Bagenal (2021) to define the centrifugal equator, along with the newest JUNO based magnetic field model (Connerney et al. 2022), and using diffusive equilibrium to find the plasma distribution along a magnetic field line. We will compare our IPT model with observations from JUNO before, during, and after the Thanksgiving 2022 eruption. We will compare JUNO observations with a physical chemistry model of the IPT to constrain the source rate, radial transport diffusion coefficient, transport timescale, and how these vary throughout the eruption.

How to cite: Nerney, E., Bagenal, F., Wilson, R., and Phipps, P.: Model Comparisons with Juno Observations of the Io Plasma Torus, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10459, https://doi.org/10.5194/egusphere-egu23-10459, 2023.

The location of the Io Plasma Torus is routinely assumed to be the centrifugal equator of Jupiter's magnetosphere, i.e. the position along the magnetic field lines farthest away from Jupiter's rotational axis. In many models, the centrifugal equator is assumed to lay on a plane, calculated from a (shifted) dipole magnetic field, rather than on a warped surface which incorporates Jupiter's higher magnetic field moments. In this work, we use Hubble Space Telescope observations of the Io Main Footprint to constrain density, scale height and lateral position of the Io Plasma Torus. We show that the leading angle of the footprints can be used to calculate expected travel times of Alfvén waves along the magnetic field lines. For the magnetic field we use the JRM33 magnetic field model. The inversion results show peak densities between 1830 / cm³ and 2032 / cm³ and scale heights between 0.92 R_J and 0.97 R_J consistent with current literature values. Using a warped multipole centrifugal equator instead of a planar dipole the quality of the fit increases by about 25 %. To evaluate these findings quantitatively, a Monte-Carlo-Test was conducted confirming that the multipole centrifugal equator explains the data much better. Furthermore, in a second set of inversion the latitudinal displacement of the torus due to quadropole moments has been fitted using a half synodic periodicity. The best fit locations are comparable to the predicted multipole centrifugal equator location, calculated from the JRM33 model. The additional half synodic periodicity of Io's orbital position inside the torus due to the incorporated quadropole moments alters Io's relative position to the torus center by about  0.15 R_{J ,} which changes the plasma density in Io's vicinity by up to 20 %. 

How to cite: Schlegel, S. and Saur, J.: The Structure of the warped Io Plasma Torus constrained by the Io Footprint, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14420, https://doi.org/10.5194/egusphere-egu23-14420, 2023.

Juno’s highly elliptical polar orbit offers unique in-situ measurements of the electrodynamic interaction between Jupiter and its moon Io. These occur both near Io and near the surface of Jupiter and at distances between. Magnetic field data obtained during multiple traversals of magnetic field lines connected to the orbit of Io reveal remarkably rich and complex current densities along flux tubes connected to Io’s position along its orbit. Using Juno’s many traversals of Io's flux tube (IFT), we derive a model of the strength of the interaction with regards to distance along Io’s extended tail and Io’s position in the plasma torus, illuminating the interaction of Jovian magnetospheric plasma with Io and setting important constraints in the Io-Jupiter interaction.The model is based on an inverse methodology to distribute currents along  the IFT in such a way as to match the magnetic field signature observed during Juno’s traversals of the IFT as well as passages near the IFT. We derive, by means of non-linear optimization, the distribution of current within the IFT (during traversals) as well as the size and morphology of the IFT that best fits the magnetic field observations. We compare our results with observations of the IFT obtained near Io as Voyager 1 passed nearby.

How to cite: Kotsiaros, S., Connerney, J. E. P., Jørgensen, J. L., Herceg, M., and Martos, Y.: A Juno model of the Io - Jupiter electromagnetic interaction, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16614, https://doi.org/10.5194/egusphere-egu23-16614, 2023.

Juno flew within 1053 km of the surface of Ganymede on June 7, 2021. A unique data set of the interaction of its magnetosphere with the magnetosphere of Jupiter was obtained during the flyby. Auroral imaging was carried out by the UVS experiment simultaneous with the in-situ sampling of the polar cap ionosphere by the Waves, MAG, JEDI, and JADE experiments onboard Juno. Significant outflow of Ganymede’s polar cap ionosphere was observed as well as an in-situ sampling of reconnection processes near the magnetospheric boundary on the flank of the trailing side of the magnetospheric interaction region. Assuming that the electrons measured in the reconnection/interaction region are representative of the electrons producing the aurora, we use the UVS auroral vertical profiles obtained from the flyby and modeling to dramatically improve our understanding of the Ganymede atmosphere. The results of the relevant flyby measurements and the modeling of the atmosphere and aurora will be presented in this talk.

How to cite: Waite, J. H., Greathouse, T., Carberry Mogan, S., Ebert, R., Connerney, J., Kurth, W., Gladstone, G. R., Allegrini, F., Johnson, R., Vorberger, A., Valek, P., Clark, G., Bolton, S., and Hansen-Koharcheck, C.: How the Juno Ganymede Flyby Has Changed our Understanding of its Aurora and Atmosphere, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9005, https://doi.org/10.5194/egusphere-egu23-9005, 2023.

On 7 June 2021 the Juno spacecraft passed through the Ganymede magnetosphere, with a closest approach altitude of 1046 km. While in the magnetosphere, the Jovian Auroral Distributions Experiment-Ion (JADE-I) sensor observed outflowing ionospheric ions. These are the first in situ observations of the ionospheric ion mass composition. The outflowing ions consist of O₂⁺, O⁺, H₂⁺, H⁺, and H₃⁺. Ion densities estimated from the measurements agree with the electron density determined by the Waves instrument to within a factor of 2.5. The light ions appear to be in hydrostatic equilibrium, and the altitude profile is generally symmetric between the inbound and outbound legs of the flyby. H₃⁺ ions are an exception to this, with the ratio of H₃⁺/H₂⁺ being ~a factor 4 lower on the outbound than the inbound leg. The heavy ions have higher densities outbound than inbound. The outflowing flux of light ions peak near closest approach, but the heavy ions peak outbound of the flyby.

How to cite: Valek, P., Waite, J. H., Allegrini, F., Ebert, R., Bagenal, F., Bolton, S., Connerney, J., Kurth, W., Szalay, J., and Wilson, R. J.: In situ ion composition observations of Ganymede’s outflowing ionosphere, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10194, https://doi.org/10.5194/egusphere-egu23-10194, 2023.

Jupiter’s plasma sheet is understood to be dominated by Io-genic material, mostly in various charge states of sulfur and oxygen. This material moves radially away from Jupiter, filling its magnetosphere. The material in the plasma sheet interacts with Europa and Ganymede, which are also sources of magnetospheric pickup ions, mostly in the form of both atomic and molecular hydrogen and oxygen. Juno’s plasma instrument JADE, the Jovian Auroral Distributions Experiment, has provided the first comprehensive in-situ observations of the composition of Jupiter’s plasma sheet with its Time-of-Flight mass-spectrometry capabilities. Here, we present observations of the magnetospheric composition in the Europa-Ganymede region of Jupiter’s magnetosphere. We highlight how Europa-genic material is often present and at times can be the dominant population for certain atomic masses, revealing a more complex and compositionally diverse magnetosphere than previously thought.

How to cite: Szalay, J., Bagenal, F., Allegrini, F., Bolton, S., Ebert, R., McComas, D., Sarkango, Y., Valek, P., and Wilson, R.: Compositional diversity of the Europa-Ganymede plasma environment, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9559, https://doi.org/10.5194/egusphere-egu23-9559, 2023.

The evolution of Juno's elliptical polar orbit has brought it close enough to Jupiter at the inbound equatorial plane crossing to intersect the orbits of the Galilean moons.  A close pass by Ganymede occurred 7 June 2021, at an altitude of 1046 km.  The spacecraft came within 350 km of Europa's surface on 29 September 2022. 

            The Juno payload, designed to probe Jupiter's magnetosphere with a comprehensive complement of fields and particles instruments, was ideal for studying Ganymede's unique mini-magnetosphere.  The spacecraft approached Ganymede from the night side, went behind Ganymede as seen from the earth (achieving an earth occultation), passed through the moon's magnetosphere, and then departed on the sunlit ~sub-jovian side.  Juno's remote sensing instruments collected new data in the visible and near-infrared, and, for the first time, mapped the surface and subsurface with 6 microwave channels.  Remote sensing of Ganymede returned new results on geology, surface composition and thermal properties of the subsurface. 

            Europa, with its tenuous atmosphere, has a unique interaction with the jovian environment, also investigated with Juno's fields and particles instruments.  The production of water molecules from sputtering of the surface is compared to the processing and eventual loss of molecules from the atmosphere.  Juno's remote sensing instruments returned high resolution images and spectra that are being used to expand our understanding of the tectonic history of Europa's surface.  The Microwave Radiometer probe of the subsurface ice shows Europa to be very different than Ganymede. 

How to cite: Hansen, C. and Bolton, S.: Overview of Juno's Results from Europa and Ganymede, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9873, https://doi.org/10.5194/egusphere-egu23-9873, 2023.

NASA’s Juno mission has been observing the Jovian aurorae 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. In particular, The
Jovian Infrared Auroral Mapper (JIRAM) is a dual-band imager and spectrometer. The 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 spectrometer is a 1-D detector with a spectral resolution of 9 nm in the range 2 - 5 µm. The
pixel angular resolution (0.01°) is fine enough for imaging the moons from the polar, highly elliptical orbit of
Juno; the spatial resolution at the surface of the moons varies along the s/c distance and is of the order of
100 km/pixel or even finer. Here we present JIRAM’s images and spectra of Io after
six years of Juno mission, together with JunoCam and SRU images of Io. On Io, these observations
characterize the location and possible morphology, and some temperatures, of the volcanic thermal
sources; the identification and distribution of SO 2 , the possible identification of CO 2 and other materials. 
Recent Juno flybys, at distance down to 50'000 km, allows unprecedented imaging of the moon with resolution of about 10 km.
This allows reconstructing the morphology of hot spots, and a better mapping of their distribution, in location and emitted power.

How to cite: Mura, A., Tosi, F., Zamboni, F., Hansen, C., Lopes, R. M., Becker, H. N., Rathbun, J., Adriani, A., Plainaki, C., Sindoni, G., and Sordini, R.: Juno observations of Io, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4351, https://doi.org/10.5194/egusphere-egu23-4351, 2023.

On 29 September 2022 Juno’s low-light Stellar Reference Unit (SRU) captured a high-resolution image (256-340 m/pixel) of a 3x10⁴ km² region of Europa’s surface between ~0-6°N and 43.5-51°W. The broadband visible image (450-1100 nm), with the highest resolution ever for that region, was collected at a sub-spacecraft altitude of 412 km during Juno’s close flyby of the icy Jovian moon while the surface was illuminated only by Jupiter-shine (incidence angle: 48-51 degrees). Prior coverage of the area by Galileo was under high-sun conditions at 1 km resolution, leading to characterization of the region as mostly ridged plain and undifferentiated linea. The SRU image reveals a much richer and complex picture; an intricate network of cross-cutting ridges and lineated bands interrupted by an intriguing 37 km (east-west) by 67 km (north-south) chaos feature that appears to be the result of a unique, local geologic process. Low-albedo deposits flank ridges near the chaos feature and bear similarity to features previously linked to hypothesized subsurface activity [Quick & Hedman, Icarus, 2020]. We will present updates to the geologic mapping of Europa enabled by the SRU image, our study of the chaos feature’s morphology, and puzzles awaiting future high-resolution imagery from Europa Clipper or JUICE.

The JPL authors’ copyright for this abstract is held by the California Institute of Technology. Government Sponsorship acknowledged.

How to cite: Becker, H., Florence, M., Lunine, J., Schenk, P., Hansen, C., Brennan, M., Bolton, S., and Alexander, J.: High resolution imagery of Europa’s Surface by Juno’s Stellar Reference Unit, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2468, https://doi.org/10.5194/egusphere-egu23-2468, 2023.

On 7 June 2021, Juno had a close flyby of Jupiter’s moon Ganymede, flying within 1000 km of the surface. During the flyby, Juno’s Microwave Radiometer (MWR) observed Ganymede obtaining several swaths across Ganymede using Juno’s spin to partially map Ganymede’s ice shell in six channels ranging from 600 MHz to 22 GHz. The radiance at these frequencies originates from successively deeper layers of the sub-surface and may reach to depths of 20km at 0.6 GHz. The MWR observations cover a latitude range from 20S to 60N and an east longitude range from -120 to 60 degrees, roughly centered on the Perrine region. The local solar time varies from around noon to mid-night over the longitude range. We present resolved brightness temperature maps and associated microwave spectra of Ganymede with a spatial resolution of up to ~140 km (approximately 1/40^th of Ganymede’s diameter). The microwave brightness temperature at all MWR wavelengths is anti-correlated with the visible brightness of the terrain, but is too large to be explained by albedo variations alone, suggesting sub-surface ice properties are not uniform with location. The dark regions tend to exhibit the warmest microwave spectra and brighter regions are observed to have a lower brightness temperature (up to half the blackbody temperature).The coldest microwave feature observed by MWR is the Tros crater and the immediate surrounding region. A radiative transfer algorithm, coupled with a thermal model for the conductive layer of Ganymede’s ice shell are fit to the MWR spectra providing an estimate of the conductive shell thickness. The microwave observations are globally colder than would be expected for pure water ice alone, suggesting thin highly reflective layer, possibly silicate dust, on the surface, although other interpretations remain possible. We suggest that scattering at sub-surface interfaces (e.g. fractures) explains the depressed brightness temperatures observed in brighter terrain types. Juno performed a close fly-by of Europa in September 2022, enabling a comparison of the sub-surface properties of these two icy satellites.      

How to cite: Brown, S., Bolton, S., Misra, S., Levin, S., Zhang, Z., Stevenson, D., Siegler, M., Feng, J., and Bonnefoy, L.: Observations of the Sub-Surface Thermal and Structural Properties of Ganymede’s Ice Shell from the Juno Microwave Radiometer, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10447, https://doi.org/10.5194/egusphere-egu23-10447, 2023.

We use the magnetic and gravity field data jointly to place constraints on the internal structure of Ganymede. The magnetic induction constraint comes mostly from the Galileo data, as the Juno flyby occurred when Ganymede was near the center of the magnetodisk, thus leading to low sensitivity to magnetic induction. The gravity field model of Ganymede jointly derived from the Galileo and Juno data to place constraints on Ganymede’s internal structure. Unlike in the previous works, the hydrostaticity was not imposed on the degree-2 gravity coefficients. Thus, despite including additional data from Juno, the uncertainties on the degree-2 coefficients increased. In addition, we explicitly treat the effect of non-hydrostaticity on the derived moment of inertia and find significantly wider confidence intervals on the moment of inertia. This leads to a larger allowed parameter space for the internal structure model.

The new gravity solution confirms the past detection of non-hydrostatic anomalies. In our analysis, localized non-hydrostatic features with amplitudes higher than those found on Titan by the Cassini mission are identified. Titan is a useful comparison case as it shares with Ganymede nearly the same mean radius, mean density, and therefore, surface gravity. Thus, the non-hydrostatic deviations of the same amplitude either in shape or in gravity would correspond to approximately the same level of non-hydrostatic stress. On Titan, the gravity field for degree l > 2 reaches at most 5 mGal (Durante et al., 2019), which is a factor of 5 smaller than the largest anomalies found on Ganymede. One key difference between the two bodies is the lack of atmosphere-based erosion processes on Ganymede. Such erosional processes could have led to faster removal of non-hydrostatic signals at Titan reducing the amplitude of its gravity anomalies. In addition, Titan’s outer shell could be thinner and, therefore, less rigid than that of Ganymede, thus not being able to support as much non-hydrostaticity.

Further insights on Ganymede’s interior will be coming from the JUICE mission in the next decade. Currently, the lack of an accurate shape model prevents separating degree-2 hydrostatic and non-hydrostatic contributions. Combined gravity, topography and rotation data acquired by JUICE will be crucial in determining the non-hydrostatic contribution to the degree-2 field to constrain Ganymede’s internal structure.

How to cite: Ermakov, A., Akiba, R., Gomez Casajus, L., Zannoni, M., Keane, J., Tortora, P., Park, R., Buccino, D., Durante, D., Parisi, M., Stevenson, D., Zhang, Z., Brown, S., Levin, S., and Bolton, S.: Ganymede’s internal structure after Juno and before JUICE., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10295, https://doi.org/10.5194/egusphere-egu23-10295, 2023.

The ESA’s Jupiter Icy moons Explorer (JUICE) L-class mission is devoted to the study of the Jovian system.

It will be launched in 2023 and, after an 8-year cruise phase (with 3 gravity assists to Earth and 1 to Venus), will start a tour of the Galilean moons that will last 3.2 years.

The onboard Geodesy and Geophysics of Jupiter and the Galilean Moons (3GM) radio science experiment will accomplish a detailed study of Europa, Ganymede and Callisto thanks to a state-of-the-art radio tacking system. 3GM will rely on a multi-frequency link enabled by two onboard units: the Ka-band Transponder (KaT) payload (establishing a full 2-way link in Ka band) and the Deep Space Transponder (DST), enabling 2-way coherent X/X and X/Ka link used for telemetry and telecommand. The multi-frequency link allows accurate measurements of range (≈1-4 cm @60s) and range rate (≈0.003 mm/s @1000s) at nearly all Sun-probe-Earth angles.

The data achieved during the tour phase (2 flybys at Europa and 21 flybys at Callisto) will be used to estimate the Europa’s quadrupole gravity field and Callisto’s static gravity field to at least degree and order 7 and its tidal Love number k₂ with an accuracy of ~0.06 [1]. This will allow 3GM to detect the presence or absence of a subsurface ocean underneath the ice shell of Callisto.

At the end of the tour phase, JUICE will be the first spacecraft to orbit around and icy satellite, allowing a comprehensive study of the moon. The Ganymede 9-month orbital phase is composed of a 5-month elliptical orbit followed by a 4-month circular orbit at 500 km of altitude (GCO-500). The mission could be extended for a 200 km altitude campaign if the residual propellant will be sufficient to decrease the orbital radius.

Range and Doppler data achieved by 3GM during the GCO-500 will be used to infer the static (up to degree 35-45) gravity field, the rotational state, and the tidal response of Ganymede.

Ganymede’s k₂ is subject to time-varying tides due to Jupiter, Io, Europa and Callisto. In particular, the Ganymede’s gravitational perturbations due to the satellites has a high spectral content. This signal can be used to estimate k₂ at a set of frequencies, up to 4d^-1. The profile of k₂ as a function of the frequency, due to the subsurface ocean, is expected to show a peak at a certain resonance frequency, its value being strictly related to the ocean’s depth. We show that the accuracy of the 3GM radio science data is sufficient to detect the peak, if present, and measure its amplitude. In this case the ocean thickness can be estimated with a 7% uncertainty [2].

References:

[1] Cappuccio, P.; Di Benedetto, M.; Durante, D.; Iess, L. (2022) Planet. Sci. J. 3 199

[2] De Marchi, F.; Cappuccio, P.; Mitri, G.; Iess, L. (2022)  Icarus 386 115150

How to cite: De Marchi, F., Cappuccio, P., Mitri, G., Iess, L., and Di Benedetto, M.: Overview of the 3GM experiment on board the JUICE mission, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12691, https://doi.org/10.5194/egusphere-egu23-12691, 2023.

Recently, the Juno and Cassini spacecraft shed light on the interior of both Jupiter and Saturn, the two gas giants of the Solar System. Juno is currently orbiting Jupiter in a highly elliptical 53.5-day orbit, with a perijove altitude of about 4000 km. After the 33rd passage in April 2021 (labeled PJ33), the mission ended its nominal mission and entered its extended mission. On the contrary, the Cassini spacecraft ended its mission on September 15th, 2017 with a deliberate plunge into Saturn’s atmosphere. In its final phase, the Grand Finale, Cassini provided insights on Saturn’s rings, atmosphere, and interior. Out of the 22 proximal orbits, six pericenter passes have been devoted to the determination of the gravity field of the planet.

The gravity science experiments on board Juno and Cassini precisely measured, respectively, Jupiter and Saturn zonal gravitational fields. The measured gravity harmonics have been used to constrain the interior structure and atmospheric zonal flow on both planets.

The Cassini data analysis have shown the need to include unknown accelerations to properly fit the data to the expected noise (Iess, 2019). Similar unexplained accelerations have been observed also on Juno gravity data (Durante, 2020). Since Jupiter and Saturn are gas giants, unconventional phenomena can be at play, including normal modes, non-zonal atmospheric dynamics, or flows in the dynamo region.

The analysis of the accelerations acting on Cassini provided evidence for p-modes on the planet (Markham, 2020), while the analysis of Juno gravity data revealed p-modes on Jupiter and provided upper bounds on lower frequency f-modes. Here, we show the results for normal modes on both Jupiter and Saturn obtained with the analysis of gravity data of both Juno and Cassini.

How to cite: Durante, D., Guillot, T., Iess, L., Stevenson, D., Mankovich, C., Markham, S., Racioppa, P., Spilker, L., and Bolton, S.: Jupiter and Saturn normal modes observed through Juno and Cassini gravity measurements, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11952, https://doi.org/10.5194/egusphere-egu23-11952, 2023.

The shape of two gas giants, Jupiter and Saturn, is determined primarily by their rotation rate, and interior density distribution. It is also affected by their zonal winds, causing a perturbation of O(10 km) at low latitudes. However, uncertainties in the observed cloud-level wind and the polar radius, translate to uncertainty in the shape with the same order of magnitude. This prevents an exact comparison against the shape based on radio-occultation measurements, the only other available data. The Juno (Jupiter) and Cassini (Saturn) missions gave unprecedentedly accurate gravity measurements, constraining better the uncertainty in the wind structure. Using an accurate shape calculation, and a joint optimization, given both gravity and radio-occultation measurements, we calculate the possible range of dynamical height for both planets. We find that for Saturn there is an excellent match to the radio-occultation measurements, while at Jupiter the shape does not reflect the radio-occultations measurements on that scale.

How to cite: Galanti, E., Kaspi, Y., and Guillot, T.: The shape of Jupiter and Saturn based on atmospheric dynamics, radio occultations and gravity measurements, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3964, https://doi.org/10.5194/egusphere-egu23-3964, 2023.

The atmospheric metallicity Z_atm of Jupiter inferred from interior models responds sensitively to assumed uncertainties in the H/He equation of state at around 10-50 GPa pressure levels and the 1-bar outer boundary temperature [1,2]. If an adiabatic temperature profile and 166 K 1-bar temperature is assumed, a perturbation toward lower densities in the 10-50 GPa region seems required for most H/He-EOSs, in order match the JUNO's gravitational harmonic J₄ value with >1x solar atmospheric  metallicity. In contrast, Galileo and JUNO measurements revealed higher atmospheric enrichments in the noble gases and ammonia of 2-3x solar. Yet for water, current uncertainties still permit lower than 1x solar in Jupiter's equatorial atmosphere [3]. 

Here, we adopt the recently proposed H/He-EOS CD21 [4] to compute a series of Jupiter interior models. We show that CD21-EOS based adiabats are less dense at ~20 GPa while denser at ~2 GPa as compared to the CMS19 H/He-EOS. The CD21 EOS allows us to lift the atmospheric metallicity by a ΔZ_atm ~1x solar when fitting J₄, while its denser behavior at 2 GPa moves the models away from the formerly good fit to J₆ that was possible with CMS19 EOS [1].

As our adiabatic models yield too low atmospheric metallicities, we insert an outer stable region, as recently suggested to explain Jupiter's magnetic field [5]. We find that a super-adiabatic stable region should occur at ~1 GPa or farther out in order to noticably influence the density in the ~50 GPa region. However, our models suggest that an outer stable region alone is insufficient to enhance the metallicity to 1x solar. Therefore, we vary in addition the 1-bar surface temperature toward warmer interiors as indicated by recent re-analysis of Voyager remote sensing data.

Overall, this work aims at predicting Jupiter's deep water abundance for comparison against formation models [6] and JUNO observations. 

[1] Nettelmann, Movshovitz, Ni et al, PSJ 2:241 (2021) 
[2] Miguel Y, Bazot M, Guillot T et al, AA 662:A18 (2022) 
[3] Li Ch, Ingersoll A, Bolton S et al, NatAst 4:609 (2020) 
[4] Chabrier G, Debras F, ApJ 917:4 
[5] Moore KM, Barik A, Stanley S, et al, JGR Planets 127:e2022JE007479 (2022)
[6] Helled R, Stevenson DJ, Lunine J, et al, Icarus 378:114937 (2022) 

How to cite: Nettelmann, N.: (Un)stable Jupiter models with CD21 H/He-EOS, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17034, https://doi.org/10.5194/egusphere-egu23-17034, 2023.

Juno is a spinning spacecraft in a highly eccentric polar orbit about Jupiter, with perijoves at about 5000 km above the cloud tops, and has completed 50 orbits as of April 2023.  From Juno’s unique vantage point, the Juno Microwave Radiometer (MWR) has measured the radio emission in 6 channels, at wavelengths ranging from 1.4 to 50 cm, with 100 mS sampling throughout each spin of the spacecraft, since the first science pass in August of 2016.  This data set covers the Jovian atmosphere over a wide range of latitudes, longitudes and emission angles, as well as observations of the inner radiation belts and of Ganymede and Europa.  MWR has yielded a number of results, as well as prompting new questions, related to Jupiter’s atmospheric composition and dynamics at depths as deep as 300 km, distribution of lightning, microwave reflection over the auroral region, Jovian synchrotron emission, and the ice shells of Ganymede and Europa. We will present an overview of MWR results to date.

How to cite: Levin, S. and the The Juno Microwave Radiometer Team: Results From The Juno Microwave Radiometer At Jupiter, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9315, https://doi.org/10.5194/egusphere-egu23-9315, 2023.

Despite the multiple evidence of the diffuse presence of methane in Jupiter’s auroral regions, the mechanisms leading to the CH₄ brightening observed both from ground- and space-based platforms are not yet fully understood. During the first NASA/Juno’s orbit, the on-board imager/spectrometer JIRAM (Jovian Infrared Auroral Mapper) detected the 3.3-µm methane emission on both Jupiter’s poles. The signal was found to be mostly confined within the main auroral ovals, although the lack of spectral coverage over 80°S prevented a deep investigation of the southern methane spot. The CH₄ polar emissions at 3.3 µm are likely originated by non-thermal excitation mechanisms occurring above the 1 µbar level, such as auroral particle precipitation and/or Joule heating. However, aurorally driven upwelling of methane inside the main oval might also explain the enhanced concentrations of CH₄ observed at the jovian poles. To address this controversy, we derive the effective temperature of methane in Jupiter’s auroral regions, which is a key information to understand the origin of the detected fluorescence. The goal is achieved by exploring three Juno’s orbits and focusing on the spectra with the highest methane emissions and the smallest contribution from other auroral features due to H₃⁺. JIRAM measurements from the first perijove are used to investigate the northern methane brightening, while observations from perijoves 7 and 8 are examined for its southern counterpart. The analysis reveals similar temperatures in the north- and south-polar spots, mainly ranging between 400 K and 670 K. 

How to cite: Castagnoli, C., Dinelli, B. M., Altieri, F., Migliorini, A., Mura, A., Adriani, A., Sordini, R., Tosi, F., Noschese, R., Piccioni, G., Moriconi, M. L., Grassi, D., Cicchetti, A., Moirano, A., Filacchione, G., Sidoni, G., Plainaki, C., Scarica, P., and Turrini, D.: Jupiter’s 3.3-micron CH4 polar brightening: Retrieval of methane effective temperature in the jovian auroral regions using Juno/JIRAM data, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3893, https://doi.org/10.5194/egusphere-egu23-3893, 2023.

We analyze the Juno microwave observations of Jupiter’s atmosphere and find a warmer interior temperature than previously assumed based on the Voyager’s radio occultation measurement (Lindal et al., 1981, JGR-Space Physics, 86.A10, 8721-8727) and the Galileo Probe (Seiff et al., 1998, JGR-Planets, 103.E10, 22857-22889). By analyzing globally averaged observations from 1.4 – 50 cm wavelength, we find that the deep isentrope of Jupiter is at  169 +/- 1 K referenced at 1 bar pressure level. The globally averaged kinetic temperature at 1-bar is closer to 175 K and Jupiter’s weather layer is stably stratified. On the other hand, the 1-bar temperature inverted from Juno microwave observations at the Equatorial Zone between 0 and 5 ^oN remains low at 166 K, consistent with the previous remote sensing measurements made at the equator from the infrared (Fletcher et al., 2016, Icarus 278, 128-161). This also implies a vertical temperature gradient at the equator which is super-adiabatic. Our results suggest that the potential temperature difference between 1-bar and the deep isentrope is approximately  2.8 +/- 1.4 K. To avoid dynamic instability, the super-adiabatic temperature gradient must be stabilized by a change of mean molecular weight within the 5 – 10 bars pressure levels which only water can provide. The result implies that an abundance of water at the equator is constrained to a value between 2.2 and 6.2 times solar.

How to cite: Li, C., Allison, M., Atreya, S., Fletcher, L., Ingersoll, A., Li, L., Orton, G., Oyafuso, F., Steffes, P., Wong, M., Zhang, Z., Levin, S., and Bolton, S.: A new value of Jupiter’s deep isentrope - implications for Jupiter’s deep thermal and compositional structure, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10747, https://doi.org/10.5194/egusphere-egu23-10747, 2023.

How to cite: Duer, K., Galanti, E., and Kaspi, Y.: Simulations of eddy-driven jets and circulation on gas giants, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11438, https://doi.org/10.5194/egusphere-egu23-11438, 2023.

Jupiter is known for its active meteorology and stormy weather, but still remaining are the questions how high are its clouds and what are they made of? Using images acquired by JunoCam, Juno’s visible light camera, we analyze the length of the clouds’ shadows to infer their heights. We focus on the “Nautilus” a 3000-km cyclonic vortex seen during Juno’s 14th perijove and observed simultaneously with the Hubble Space Telescope. We show that individual clouds or cloud fronts with typical lengths of ∼200 km extend about ∼10 to 20 km above the deeper surrounding cloud deck. That white cloud deck forms the spiral of the cyclone, which we show lies ∼20 to 30 km above a reddish-colored region. An analysis of the HST images 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.

How to cite: Guillot, T., Rosenqvist, M., Wong, M., Orton, G., Eichstädt, G., Brueshaber, S., Keaveney, C., Hansen, C., Kelley, K., Momary, T., Lunine, J., Mayer, J., and Bolton, S.: How high are Jupiter’s clouds? Analysis of JunoCam images of the “Nautilus”, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17178, https://doi.org/10.5194/egusphere-egu23-17178, 2023.

The micro Advanced Stellar Compass (µASC), an instrument onboard Juno serving as attitude reference for the Juno Magnetic Field investigation, providing accurate bias free attitude information continuously throughout the mission. The µASC is equipped with four optical sensors, configured for low-light scenarios, which enables detection of stars and objects as faint as 7-8Mv.

During each perijove passage the highly elliptical Juno orbit configuration, in combination with the 13° off pointing of the star tracker cameras from the Juno spin axis in the anti-sun direction, enables observations of the Jupiter horizon at a high slant angle. During such observation opportunities, the Jovian horizon is some 40,000km distant, offering detailed imaging of the upper atmosphere, luminous phenomenon herein, as well as any haze layer or elevated clouds, before the planet atmosphere transitions into the dark space star field. The orbital motion of Juno, further result in continuous occultation’s of stars setting behind the horizon.

After 40+ perijoves such images have been acquired from the µASC, distributed from Jupiter North Pole down to +30deg of latitude at a wide range of longitudes. This coverage enables altitude profiling of the top atmosphere as described by latitude and longitude for both dusk and dawn conditions of Jupiter.

Images and objects observed by the aforementioned technique are presented together with the detected energies within the sensitivity range of the observing star tracker camera and their implications for the atmospheric density profile.

How to cite: Benn, M., Jørgensen, J. L., Jørgensen, P. S., Denver, T., Herceg, M., and Connerney, J. E.: Jupiter's Atmosphere Profiling, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12234, https://doi.org/10.5194/egusphere-egu23-12234, 2023.

Juno spacecraft has observed large-scale circumpolar vortices on Jupiter’s both poles. It remains unclear how these large-scale vortices are generated and maintained. Here we propose a deep model to explain their formation and maintenance. From numerical simulations, we find that the polygonal patterns of circumpolar vortices can be naturally formed in a deep rotating convection and maintained for a long time. Several processes are involved in the formation of the circumpolar vortices. Small cyclonic vortices are generated from random turbulence in rotating convection at first. Then these small vortices merge and grew bigger to form large-scale cyclones. Finally, the polar beta effect pushes the large-scale cyclones to form a polygonal pattern around the pole. Our model suggests that Jupiter’s circumpolar vortices probably are deeply rooted. This work was supported by the Science and Technology Development Fund, Macau SAR through No. 0156/2019/A3.

How to cite: Cai, T., Chan, K., and Mayr, H.: A Deep Model on Jupiter’s Circumpolar Vortices, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17402, https://doi.org/10.5194/egusphere-egu23-17402, 2023.

Data analysis of Juno MWR instrument measurements of brightness temperature at six channels showed that ammonia vapor was depleted in the region between ammonia cloud base all the way down to 40-60 bars. The vertical extent of depletion is far greater than previous thought, which assumed that ammonia in the sub-cloud layers were well mixed. We use a state-of-the-art Global Circulation Model (GCM), JupiterMPAS, to investigate the physical and dynamical processes below the water cloud base in hoping to interpret water and ammonia abundances retrieved over a wide range of latitudes. Two mechanisms that may affect ammonia distributions have been examined: “mushball” microphysics and mesoscale circulations. JupiterMPAS model results show that: 1. the mushball microphysics is a viable method to produce ammonia depletion in the region above water cloud base; 2. the treatment of lower boundary conditions in the JupiterMPAS model can impact tracer distribution in the sub-cloud layers; 3. depletion of ammonia via strong mesoscale downdrafts is possible, but its effect on global ammonia distribution is very limited.

How to cite: Lian, Y., Guillot, T., Ingersoll, A., and Li, C.: Global and Regional Numerical Modeling of Water and Ammonia Cycles on Jupiter, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9336, https://doi.org/10.5194/egusphere-egu23-9336, 2023.

The outer regions of both Gas Giants in our Solar System, Jupiter and Saturn, feature strong, alternately Eastward and Westward moving zonal winds. Cloud tracking has yielded latitudinal profiles of these winds, which are longitudinally invariant and steady in time to a high degree and reach all the way to the polar regions. However, reproducing these features in numerical simulations has proved difficult as certain physical transitions at various depths are required to both enable winds to form and be maintained at the higher latitudes, and then be quenched at the depths inferred from gravity measurements.
A sub-adiabatic region in combination with an increase in electrical conductivity seems to be key, but makes the dynamics rather complex. In this study we analyse how the two transitions affect the zonal winds formed in an overlying convecting region, as well as how they then penetrate into the respective stably stratified and dynamo regions.
Particularly in the case of Jupiter evidence is accumulating for a stably stratified layer, shallower than where Helium rain may be expected, based on interior models and magnetic field modelling. However, the nature of such a shallower layer and its exact depth is still very undetermined. This study helps to constrain the depth at which this stratified region begins relative to the depth of the transition into the dynamo region. We find that when the transition to high electrical conductivity is much deeper than the transition into the stable region, zonal winds form at all latitudes. When the boundary of the dynamo region becomes shallower, high-latitude jets are diminished in amplitude and cease to reach the polar regions.

How to cite: Wulff, P., Christensen, U., Dietrich, W., and Wicht, J.: The Effects of a Stably Stratified Region on the Formation of Zonal Winds on Gas Planets, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15308, https://doi.org/10.5194/egusphere-egu23-15308, 2023.

How to cite: Louis, C., Kurth, W., Bolton, S., Boudouma, A., Collet, B., Elliott, S., Hospodarsky, G., Imai, M., Jackman, C., Lamy, L., Louarn, P., Martos, Y., Sulaiman, A., and Zarka, P.: New insights into Jovian radio emissions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17132, https://doi.org/10.5194/egusphere-egu23-17132, 2023.

The Juno spacecraft, in polar orbit about Jupiter since July 2016, continues to map the gas giant’s complex magnetic field with ever-increasing resolution in space and time. Comparison of spherical harmonic models (JRM33 and JRM09) derived from Juno measurements representative of different epochs revealed secular variation of the field near the isolated and intense patch of negative flux near the equator known as the Great Blue Spot (GBS). The feature drifts eastward relative to the deep interior at a rate of a few cm/s; if carried at depth by zonal winds, they must penetrate to depths of ~3000 km where the electrical conductivity is sufficient to grip the magnetic field. A dedicated magnetic survey above the GBS was conducted during Extended Mission orbits 36-42 to better characterize the GBS and its evolution during the mission; another is under consideration for later in the mission. 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) via a new spherical harmonic analysis allowing for time-dependent dipole coefficients. The drift of the dipole during Juno’s prime mission (by 0.12°/yr) determined this way yields an improved planetary rotation period of 9h 55m 29.698s, if the migration of the dipole is attributed to the limited accuracy of the IAU adopted planetary rotation period. A similar result is obtained by comparison of the JRM33 model with models representing earlier epochs (Voyager in 1979 and Ulysses in 1992). If time permits, we will also discuss particle motion in the complex (high degree and order) magnetic field near Jupiter’s surface and its relevance to local particle fluxes.

How to cite: Connerney, J., timmins, S., jorgensen, J., Kotsiaros, S., Jorgensen, P., Herceg, M., Bloxham, J., Bolton, S., and Levin, S.: Jovimagnetic Secular Variation and Jupiter’s rotation Period, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10373, https://doi.org/10.5194/egusphere-egu23-10373, 2023.

We study Jupiter’s magnetic field and plasma parameters during Juno’s prime mission, using data from Juno’s FGM magnetometer and ion measurements from the  Jovian Auroral Distributions Experiment Ion (JADE-I) sensor on Juno.  We compare the observed poloidal magnetic field and  plasma density, angular velocity and temperature profiles, with predictions from the Nichols et al. (2015)  axisymmetric magnetic vector potential model.  This  magnetodisc model balances the j x B force of the azimuthal magnetodisc currents with the outwards forces of the plasma pressure gradient, plasma pressure anisotropy and the centrifugal force associated with the rotating plasma.  By varying the model parameters for each orbit we model how Jupiter’s mass outflow rate, plasma angular velocity and ‘hot’ and ‘cold’ plasma temperatures and densities vary throughout Juno’s prime mission.  We further examine how changes in magnetospheric conditions are related to variations in the magnetosphere–ionosphere coupling parameters, in particular by studying the azimuthal and radial currents and the ionospheric field-aligned current density. 

How to cite: Provan, G., Nichols, J., Cowley, S., Wilson, R., Bagenal, F., and Connerney, J.: Jupiter’s magnetodisc and magnetospheric currents during Juno’s prime mission., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14691, https://doi.org/10.5194/egusphere-egu23-14691, 2023.

The Advanced Stellar Compass (ASC), part of the MAG experiment onboard Juno, has been measuring the Jovian high energy particle environment since orbit insertion. We’ve produced a detailed map of the distribution of trapped high energy particles, predominantly electrons (>10MeV), using data from Juno’s first 47 orbits. The observations also demonstrate the significant influence that space weather at Jupiter has on the local particle flux. The ASC is a star tracker designed with four low light cameras to provide accurate attitudes for the MAG experiment’s vector magnetometers, located on a boom at the end of one of the spacecraft solar wings at 10 and 12m from the center of the spacecraft. At this location the ASC cameras are subjected to the high energy particle omniflux for all 4pi.  Electrons with an average energy of 20MeV and protons with energy in excess of 100MeV will pass through the camera radiation shielding to the camera CCDs to liberate signal electrons. To enable robust attitude estimation, the signal from the penetrating radiation is first removed by a software filter before star field recognition is performed. Registering the particle count in each image, these measurements effectively provide for a high time resolution measurement of the high energy particle omniflux. We present the detailed map of high energy particles throughout Jupiter’s magnetosphere and demonstrate how the local flux responds to solar activity.

How to cite: Jørgensen, J., Denver, T., Herceg, M., Sushkova, J., Connerney, J., Toldbo, C., Benn, M., Bolton, S., and Levin, S.: Jupiters high energy particle environment observed by Juno, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14751, https://doi.org/10.5194/egusphere-egu23-14751, 2023.

We present simultaneous Juno and Hubble Space Telescope of Jupiter's far-ultraviolet auroras obtained as part of a programme of observations covering 3 years of Juno's Extended Mission.  We show that bright, expanded dusk-side southern main emission is associated with large-scale convection dynamics, dusk-side main emission arcs are associated with field-aligned currents, and equatorward diffuse emission and patches are associated with plasma injections in the middle magnetosphere occurring within intervals of enhanced plasma density, ongoing interchange motion and magnetospheric convection.  These results shed light on the relation between the main auroral emission and magnetosphere-ionosphere coupling currents, and radial force balance in the magnetosphere. We also report on unusually bright and expanded southern auroral emissions observed during PJ 43.

How to cite: Nichols, J. D., Clarke, J., Grodent, D., Bonfond, B., Cowley, S., Gladstone, R., Bagenal, F., Orton, G., Lysak, B., Allegrini, F., Connerney, J., Mauk, B., Clark, G., Wilson, R., and Ebert, R.: Hubble and Juno observations of Jupiter’s auroras and magnetospheric dynamics during the Juno Extended Mission, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16086, https://doi.org/10.5194/egusphere-egu23-16086, 2023.

Gyroresonant wave-particle interactions with whistler mode chorus waves plays a dual role in the precipitating loss and acceleration of energetic electrons in Jovian magnetosphere, which plays fundamental role in both Jovian radiation belt dynamics and auroral emission. Knowledge of the chorus wave power as a function of multi-dimensional spatial location and their spectral distribution are critical inputs for Jovian radiation belt modeling. In this work we present a global, analytical model of the typical Jovian chorus waves (0.1f_ce<f<0.8f_ce) based on the measurements made by Juno spacecraft in orbits 1 through 45, with which the whole nightside sector is covered. The radial, latitudal and local time dependence of the chorus wave intensity are derived. Mean-squared and most-probable spectral distributions are also statistically in separated M-shell and magnetic latitude sectors. With the updated chorus wave model, the wave-particle interaction is further quantified in terms of pitch angle, energy and mixed diffusion coefficients. We present an estimation of electron loss rate due to pitch angle scattering and henceforth precipitating to Jovian atmosphere in the format of electron lifetime as a function of energy and M-shell.

How to cite: Hao, Y., Wang, D., Shprits, Y., Menietti, J., and Drozdov, A.: Global Model of Chorus Waves and Electron Lifetime Derived From Juno Observations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16574, https://doi.org/10.5194/egusphere-egu23-16574, 2023.

Decametric radio emissions (DAM) originating in Jupiter’s polar magnetosphere ought to originate on magnetic field lines at the local electron gyrofrequency. The Io-related DAM have received the most attention since the 1980’s. The maximum frequency of these emissions ought to be bounded by the maximum magnetic field strength above the footprint of the instantaneous Io Flux Tube (IFT). However, there remains a lack of agreement between the frequency extent of Io-related decameter radiation and the frequency extent predicted by Jovian magnetic field models. Here, we analyze peak frequencies and source locations of Io and non-Io-related DAM observed by Juno during the prime mission (~10,600 events) and show how the latest magnetic field model can accommodate and control Io-DAM. We note that the observed peak frequencies appear to be truncated at 37 MHz although the magnetic field in the northern hemisphere would allow events to 55 MHz at some longitudes. Lower frequencies than the ones allowed by the magnetic field are consistently observed for most of the Io’s longitude. To reconcile this discrepancy, we analyze the upper electron density limit distribution along the magnetic field lines, the possible existence of plasma cavities and the locations in the magnetosphere where the extraordinary mode is no longer achieved. For this, we make use of beaming angles of Io-DAM and the geometry of the Jovian magnetic field.

How to cite: Martos, Y. M., Connerney, J., Imai, M., Farrell, W., and Kurth, W.: Jupiter’s magnetic field and the generation and control of decameter radiation observed by the Juno spacecraft during the prime mission, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17133, https://doi.org/10.5194/egusphere-egu23-17133, 2023.

During transit from Earth to Jupiter, NASAs Juno spacecraft carried out scientific measurements along its trajectory, using a subset of its instrument suite. One of the instruments turned on during the journey was the micro Advanced Stellar Compass, part of the MAG investigation. The fully autonomous microASC uses a camera to image the sky for attitude determination, its primary function, but it also logs objects appearing multiple times in the camera FOV that are not found in the instrument’s star catalog. In doing so, it routinely logged the motion of illuminated spallation products evolving from the impacts of interplanetary dust particles (IDPs) on the spacecraft. The system is capable of detection of IDPs with a diameter larger than ~5µm, i.e. particles in the size range responsible for the Zodiacal light. The detection mode was activated just after Juno performed a deep space manoeuver at 2.2AU setting the spacecraft up for a gravity assist from a close Earth flyby, sending Juno on a trajectory to rendezvous with Jupiter. The first leg of the journey, from 2.2AU to 0.8AU and to the Earth flyby, was in the ecliptic plane, whereas the trajectory from Earth to Jupiter rose well above the ecliptic plane. This resulted in measured IDP density profiles both in and above the ecliptic plane. In December 2015, half a year before Jupiter orbit insertion, a conspicuously high rate of dust impacts was detected for a fortnight. A closer analysis showed that Juno happened to pass through the tail of a Jupiter family comet.

We here present the observations of the particle population during the December 2015 event, discuss the dust tail evolution and morphology, and present the implications for the comet’s size and volatility.

How to cite: Jørgensen, P. S., Jørgensen, J. L., Connerney, J. E. P., Toldbo, C. A., Benn, M., Andersen, A. C., Denver, T., and Bolton, S. J.: Comet dust tail detection by the Juno spacecraft’s magnetometer investigation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11490, https://doi.org/10.5194/egusphere-egu23-11490, 2023.