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We study the release of various elements from Callisto's surface into its exosphere by plasma sputtering. The cold Jovian plasma is simulated with a 3‐D plasma‐planetary interaction hybrid model, which produces 2‐D surface precipitation maps for magnetospheric H+, O+, O++, and S++. For the hot Jovian plasma, we assume isotropic precipitation onto the complete spherical surface. Two scenarios are investigated: one where no ionospheric shielding takes place and accordingly full plasma penetration is implemented (no‐ionospherescenario) and one where an ionosphere lets virtually none of the cold plasma but all of the hot plasma reach Callisto's surface (ionospherescenario). In the 3‐D exosphere model, neutral particles are sputtered from the surface and followed on their individual trajectories. The 3‐D density profiles show that whereas in the no‐ionosphere scenario the ram direction is favored, the ionosphere scenario produces almost uniform density profiles. In addition, the density profiles in the ionosphere scenario are reduced by a factor of ∼2.5 with respect to the no‐ionosphere scenario. We find that the Neutral Gas and Ion Mass Spectrometer, which is part of the Particle Environment Package on board the JUpiter ICy moons Explorer mission, will be able to detect the different sputter populations from Callisto's icy surface and the major sputter populations from Callisto's nonicy surface. The chemical composition of Callisto's exosphere can be directly linked to the chemical composition of its surface and will offer us information not only on Callisto's formation scenario but also on the building blocks of the Jupiter system. We investigate Callisto's surface sputtered exosphere; two cases are investigated: one with an ionosphere present and one with no ionosphereThe case where no ionosphere is present produces an asymmetric exosphere, with favoring of the ram direction (direction of plasma arrival)With an ionosphere present, the exosphere is almost uniform, and densities are ∼2.5 times lower than in the case without an ionosphere

The solar wind interaction with Ceres is studied for a high water vapor release from its surface using a hybrid model including photoionization. We use a water vapor production rate of 6 kg/s, thought to be due to subsurface sublimation, corresponding to a detection on 6 March 2013 by the Herschel Space Observatory. We present the general morphology of the plasma interactions, both close to Ceres and on a larger scale. Mass loading of water ions causes a magnetic pileup region in front of Ceres, where the solar wind deflects up to 15° and slows down by 15%. The global plasma interaction with Ceres is not greatly affected by the source location of water vapor nor on gravity, only on the production rate of water vapor. On a global scale, Ceres has a comet‐like interaction with the solar wind with observable perturbations farther than 250 Ceres radii downstream of the body. The general morphology of the solar wind interaction with Ceres and the associated water vapor, using a hybrid model including gravityCeres has a strong interaction with the solar wind. This is of general interest and will inform future missions to CeresOn a global scale Ceres interacts with the solar wind like a weak comet, as gravity, obstacle, source location, have no significant effect

Alfvén wings are known to form when a conducting or mass‐loading object slows down a flowing plasma in its vicinity. Alfvén wings are not expected to be generated when an inert moon such as Rhea interacts with Saturn's magnetosphere, where the plasma impacting the moon is absorbed and the magnetic flux passes unimpeded through the moon. However, in two close polar passes of Rhea, Cassini clearly observed magnetic field signatures consistent with Alfvén wings. In addition, observations from a high‐inclination flyby (Distance > 100 RRh) of Rhea on 3 June 2010 showed that the Alfvén wings continue to propagate away from Rhea even at this large distance. We have performed three‐dimensional hybrid simulations of Rhea's interaction with Saturn's magnetosphere which show that the wake refilling process generates a plasma density gradient directed in the direction of corotating plasma. The resulting plasma pressure gradient exerts a force directed toward Rhea and slows down the plasma streaming into the wake along field lines. As on the same field lines, outside of the wake, the plasma continues to move close to its full speed, this differential motion of plasma bends the magnetic flux tubes, generating Alfvén wings in the wake. The current system excited by the Alfvén wings transfers momentum to the wake plasma extracting it from plasma outside the wake. Our work demonstrates that Alfvén wings can be excited even when a moon does not possess a conducting exosphere. Alfvén wings are expected near conducting moons but are not expected in an interaction of an inert moon with plasmaRhea is an inert moon, but in two close and a distant flyby, we observed Alfvénic structures in its wakeWe show that the wake refilling process generates a plasma pressure gradient that slows plasma in the wake and generates Alfvén wings

By using a hybrid plasma solver (ions as particles and electrons as a fluid), we have modeled the interaction between Callisto and Jupiter's magnetosphere for variable ambient plasma parameters. We compared the results with the magnetometer data from flybys (C3, C9, and C10) by the Galileospacecraft. Modeling the interaction between Callisto and Jupiter's magnetosphere is important to establish the origin of the magnetic field perturbations observed by Galileoand thought to be related to a subsurface ocean. Using typical upstream magnetospheric plasma parameters and a magnetic dipole corresponding to the inductive response inside the moon, we show that the model results agree well with observations for the C3 and C9 flybys, but agrees poorly with the C10 flyby close to Callisto. The study does support the existence of a subsurface ocean at Callisto. General morphology of the plasma interaction with Callisto using a hybrid modelComparison between the model and Galileomagnetic field observationsBest fit with observations if induction from a subsurface ocean is included