Water-group gas continuously escapes from Jupiter’s icy moon Europa in both charged and neutral states. The neutral species form co-orbiting populations of particles, or neutral toroidal clouds, eventually becoming ionized to be incorporated into the Jovian plasma environment. In September 2022, Juno performed a close flyby at ~350 km, an altitude less than the satellite’s radius, allowing it to make direct observations of water-group pickup-ions originating from the moon’s surface. These observations, along with more remote measurements by Juno of Europa-genic water-group pickup ions, provide critical constraints on the evolution and loss processes of Europa’s icy surface. We will present direct observations of water-group pickup-ions from Europa in the context of understanding the breakdown and evolution of Europa’s surface ice.

How to cite: Szalay, J., Allegrini, F., Ebert, R., Bagenal, F., Bolton, S., Fatemi, S., McComas, D., Pontoni, A., Poppe, A., Sarkango, Y., Saur, J., Smith, T., Valek, P., Vance, S., Vorburger, A., and Wilson, R.: Water-group pickup ions from Europa: A window into surface ice evolution, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9404, https://doi.org/10.5194/egusphere-egu23-9404, 2023.

The JUpiter ICy moons Explorer (JUICE) mission is the first large-class (L1) mission of ESA Cosmic Vision. JUICE will be launched in April 2023 with an arrival at Jupiter in 2031 and at least four years making detailed observations of Jupiter’s magnetosphere and of three of its largest moons (Ganymede, Callisto and Europa). The Radio and Plasma Wave Investigation (RPWI) consortium will carry the most advanced set of electric and magnetic fields sensors ever flown in Jupiter’s magnetosphere, which will allow to characterize the radio emission and plasma wave environment of Jupiter and its icy moons. Here we present the scientific objectives and the technical features of the Search Coil Magnetometer (SCM) of RPWI. SCM will provide for the first time three-dimensional measurements of magnetic field fluctuations in the frequency range 0.1 Hz – 20 kHz within Jupiter’s magnetosphere. High sensitivity (~10 fT / √Hz at 1 kHz) will be assured by combining an optimized (20 cm long) magnetic transducer with a low-noise (4 nV / √Hz) ASIC pre-amplifier. Perturbations by the spacecraft are strongly reduced by accommodating SCM at about 10 m away from the spacecraft on the JUICE magnetometer boom. The combination of high sensitivity and high cleanliness of SCM measurements will allow unpreceded studies of electromagnetic fluctuations down to plasma kinetic scales, in particular in key regions such as the magnetopause, the auroral region and the magnetotail current sheet of Ganymede’s own magnetosphere which JUICE will orbit for many months. This will lead to important advances in understanding how fundamental plasma processes such as magnetic reconnection, turbulence and particle energization occur in Jupiter’s plasma environment.

How to cite: Retinò, A., Mansour, M., Canu, P., Chust, T., Hadid, L., Le Contel, O., Sahraoui, F., Zouganelis, I., Alison, D., Ba, N., Jeandet, A., Mehrez, F., Mirioni, L., Piberne, R., Berthod, C., Geyskens, N., Sou, G., Cecconi, B., Bergman, J., and Wahlund, J.-E.: The Search-Coil Magnetometer (SCM) of the Radio and Plasma Waves Investigation (RPWI) onboard the ESA JUICE mission, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7689, https://doi.org/10.5194/egusphere-egu23-7689, 2023.

Recent Juno microwave observations have revealed puzzling features of Jupiter’s ammonia distribution, including an ammonia-poor layer extending down to levels of tens of bars outside the equatorial region to at least ±40° [Li et al. 2017]. Guillot et al. [2020] showed that ammonia-rich hail, or “mushballs”, formed during a powerful thunderstorm, can efficiently transport ammonia to the deeper atmosphere and hence could cause the observed ammonia depletion. However, this mechanism has not been tested in numerical simulations in which convective events are self-consistently determined. 
We have developed a simple parameterization scheme for the mushball process and implemented it into a Jupiter GCM [Young et al. 2019] that includes the following relevant parameterizations: a simple cloud microphysics model for water and ammonia, a water moist convection scheme that transports ammonia as a passive tracer, a dry convection scheme, and a two-stream, semi-grey radiative transfer scheme. In the two-dimensional setup of the aforementioned GCM, we show that mushball precipitation can produce an ammonia depletion qualitatively similar to the Juno observations.
We present our preliminary results in three-dimensional simulations, in which a Jupiter-like zonal jet profile emerges spontaneously. We will show the role of different processes, including the mushball process, moist convection and meridional circulation in shaping ammonia distribution. Further, we compare our model output with Juno MWR result, and discuss the implication to future observations.

How to cite: Hu, X., Read, P., Parmentier, V., and Colyer, G.: Effect of Mushball on Jupiter's Ammonia Distribution: a General Circulation Model Study, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-826, https://doi.org/10.5194/egusphere-egu23-826, 2023.

Galactic cosmic rays (GCRs), primarily consisting of protons, are ubiquitous throughout the solar system. The greatest source is supernova activity and the flux in the solar system is modulated by the solar wind. Planets can be shielded if they possess a magnetic field. Jupiter’s magnetic field is the strongest in the solar system and has several interesting features such as the Great Blue Spot near the Equator. The JUNO satellite has mapped the magnetic field of Jupiter in great detail (Connerney et al, JGR Planets 127(2), 2022) resulting in the JRM33 model, composed of data from 32 polar orbits of JUNO around Jupiter.

We have calculated a cosmic ray cutoff rigidity map for Jupiter. This was done using a modified version of a particle trajectory program (the Geomagnetic Cutoff Rigidity Computer Program by Smart and Shea (2001, Tech. Rep. No. 20010071975)) with the first 12 degrees and orders of the spherical harmonic expansion from the JRM33 model as input. This is done for vertical GCR entry into Jupiter’s atmosphere at a height of 67.5 km above the 1 bar level and for distances further out where high energy particles have been detected by JUNO. The energies required to enter into Jupiter’s atmosphere varies by several orders of magnitude from above 2500 GeV at locations around the Great Blue Spot and going downwards towards the poles.

The modulation of the GCR proton flux into Jupiter’s atmosphere was then calculated. For the incoming GCR spectrum we used data from the BESS-POLAR II Antarctic mission (Abe et al, ApJ 822(2), 2016), collected at solar minimum where the modulation by the solar wind is at its lowest. By fitting the measured spectrum and using the calculated cutoff rigidities we have made a map of the proton flux into Jupiter’s atmosphere.

Finally, we have investigated several incidents of high energy heavy ion detections by JUNO (Becker et al, JGR Planets 126, 2021) by calculating the cutoff rigidities from several incoming angles at the locations where JUNO made the detections and along the corresponding M-shells.

How to cite: Enghoff, M. B., Svensmark, J., Jørgensen, J. L., Herceg, M., Kotsiaros, S., and Connerney, J. E. P.: Galactic Cosmic Ray Cutoff Rigidities and Flux at Jupiter, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5439, https://doi.org/10.5194/egusphere-egu23-5439, 2023.

The future JUICE and Europa Clipper missions will probe the Jovian system performing several flybys of the moons Europa, Ganymede, and Callisto. The precise radio tracking data will provide an accurate estimation of the gravity and ephemerides of the Galilean moons. This is especially true for Ganymede, after JUICE insertion in a low circular orbit around the moon for at least four months. The evolution of the orbits of the Galilean moons will allow for an estimation of the dissipation in Jupiter at the orbital frequency of each Galilean moon, represented/parameterized through the imaginary part of its degree-2 Love number.

The imaginary part of the Jovian Love number  is a key parameter to evaluate the long-term orbital evolution of the Galilean moons and the Laplace resonance stability. Its secular effect on the orbit of the moons produces an acceleration both in the radial and tangential direction, and the longer the time span of observation, the better it can be estimated. However, the dissipations at the different satellite orbital frequencies are highly correlated due to the Laplace resonance, complicating their estimation. 

JUICE and Europa Clipper missions cover less than 5 years, but the accuracy in the determination of the moon’s orbit is good if not exquisite. This broad data set can be complemented by high quality astrometry measurements collected by ground observatories starting from 1891, past spacecraft missions (Voyager, Galileo) optical images and radar data. This approach has the potential to greatly improve the estimation accuracy for the dissipation parameters in Jupiter.

Future work will include the addition of radio-tracking measurements from the spacecraft Galileo and Juno, which together with JUICE and Europa Clipper will offer a 30 year time span of radio-metric data.

Unfortunately JUICE and Clipper, unlike Galileo and Juno, will fly never by Io, the moon which dominates the evolution of the Laplace resonance and the dissipation in the Jovian system. However Io can be observed from ground telescopes, and the available astrometric observations of the moon may allow a significant reduction of Io’s state solution uncertainties and correlations.

In this study, we analyze the attainable uncertainties for the parameters characterizing the dissipation in Jupiter’s system and the ephemerides of the Galilean moons combining simulated range & range-rate radio tracking data from JUICE and Europa Clipper with astrometry data, showing the synergies and the possible improvements in the uncertainties and correlations of the joint analysis, together with a discussion of the problems associated to the fusion of data sets of very different type.

How to cite: Magnanini, A., Fayolle, M., Lainey, V., Zannoni, M., Dirkx, D., Tortora, P., Mazarico, E., and Iess, L.: Jupiter’s Frequency-Dependent Love Number estimation through joint analysis of JUICE-3GM and Europa Clipper radio science measurements and one century of astrometry data, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12536, https://doi.org/10.5194/egusphere-egu23-12536, 2023.

The Jovian magnetosphere can undergo significant changes in its size due to varying external (e.g. solar activity) or internal (e.g. hot plasma pressure) conditions. Simulations have shown that the difference in the dayside stand-off distance between a compressed and an expanded state can be around 30 Jovian radii.

In this work, we study the compressibility of the Jovian magnetosphere using a large ensemble of axisymmetric models, obtained from the recently updated UCL/AGA magnetodisc code. Each model is defined by its size (via the stand-off distance) and hot plasma content (via the hot plasma index). Using these models as virtual magnetopause crossings we estimate the compressibility index, calculated via changes in the dayside stand-off distance as a function of the external pressure, which characterises the overall response of the magnetosphere.

We find that the system size plays an important role in the Jovian case, as we observe a change in the compressibility index as a function of the stand-off distance. This has also been noted in existing studies on Saturn, using a linear relation between changes in the stand-off distance and the external pressure.

As a complementary study, we also estimate the compressibility index using magnetopause crossings from recently published catalogues based on JUNO data.

How to cite: Millas, D., Achilleos, N., Guio, P., and Arridge, C. S.: Investigating the compressibility of the Jovian magnetosphere, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15246, https://doi.org/10.5194/egusphere-egu23-15246, 2023.

Mirror modes are large amplitude, non-propagating compressive structures often observed in the magnetosheath. They appear in the form of quasi-sinusoidal oscillations in the magnetic field, with clear magnetic dropouts (‘dips’) or enhancements (‘peaks’). Mirror modes are usually accompanied by a corresponding, anticorrelated signature in plasma density. Typically, the growth of mirror mode fluctuations is triggered when magnetized plasma traverses the bow shock (BS) or draping of the magnetic field around the magnetopause (MP), producing anisotropic ion distribution functions in a high plasma β environment.

In this work, nine years of in-situ Cassini data and the latest published catalogue of BS and MP crossings at Saturn were used to perform a detailed statistical analysis of magnetic fluctuations associated with mirror mode structures in Saturn’s magnetosheath. 182 single traversals through the magnetosheath between the bow shock and the magnetopause were used to study the evolution of mirror mode structures across Saturn’s outer and inner magnetosheath and to assess the effects of magnetic shear at the MP on the mirror mode structures near the MP. Violante et al. (1995) analysed two MP crossings at Saturn by Voyagers 1 and 2 and found that in the high magnetic shear MP, mirror waves appear with increasing amplitude and decreasing frequency until the MP, whilst in the other low magnetic shear case, the mirror waves ceased to grow in the presence of a plasma depletion layer but are still present, albeit with smaller amplitude.

The amplitude and frequency of mirror waves near the magnetopause are also examined against signs of magnetic reconnection. Tsurutani et al. (1982) suggested that the amplitude of mirror wave structures could impact magnetic reconnection at the MP boundary as alternating high and low regions and the plasma temperature anisotropies may lead to patchy and sporadic reconnection.

How to cite: Cheng, I. K. and Achilleos, N.: The role of magnetic shear on the evolution of mirror mode waves and their influence on magnetic reconnection at Saturn’s magnetopause, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16080, https://doi.org/10.5194/egusphere-egu23-16080, 2023.

Determining the composition of giant exoplanets is crucial for understanding their origin and evolution. However, the planetary bulk composition is not measured directly but must be deduced from a combination of mass-radius measurements, knowledge of the planetary age and evolution simulations. Accurate determinations of stellar ages, mass-radius, and atmospheric compositions from upcoming missions can significantly improve the determination of the heavy-element mass in giant planets. In this talk, we first demonstrate the importance of an accurate age measurement, as expected from Plato, in constraining the planetary properties. Well-determined stellar ages can reduce the bulk-metallicity uncertainty up to about a factor of two. We next infer the bulk metallicity of warm giants from the Ariel mission reference sample and identify the Ariel high-priority targets for which a measured atmospheric metallicity can clearly break the degeneracy in the inferred composition. We show that a knowledge of the atmospheric metallicity can broadly reduce the bulk-metallicity uncertainty by a factor of four to eight. We conclude that the accurate age determination from Plato and atmospheric measurements by Ariel and the James Webb Space Telescope will play a key role in revealing the composition of giant exoplanets.

How to cite: Müller, S. and Helled, R.: Towards a new era in giant exoplanet characterisation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11036, https://doi.org/10.5194/egusphere-egu23-11036, 2023.