Modeling the interactions between Callisto’s neutral and ionized environments and the Jovian magnetosphere

Callisto is the most distant of the four Galilean moons, orbiting at around 26.3 Jovian radii from its planet. Composed of equal parts rock and ice, the moon has a tenuous atmosphere composed mainly of O₂ [Cunningham et al., 2015] and CO₂ [Carlson, 1999], as well as an ionosphere characterized by densities of up to 10⁴ cm⁻³ [Kliore et al., 2002]. The moon’s environment interacts with the Jovian magnetosphere (surface erosion, Alfvén wings, etc.), whose physical characteristics vary greatly during its orbit, with a wide excursion in magnetic latitude. Due to a time-varying magnetic environment, electromagnetic induction occurs at Callisto in its ionosphere [Hartkorn & Saur, 2017], but also in a potential subsurface liquid ocean, as it was observed by NASA’s Galileo mission during flybys of the moon [Zimmer et al., 2000; Cochrane et al., 2025].

While the JUICE mission plans to carry out several flybys of Callisto, the interaction between the moon and Jupiter’s magnetosphere remains poorly understood. Simulations describing the neutral and ionized environments of the Jovian satellite must therefore be set up. The Larmor radii of freshly generated pick-up ions of O₂⁺ and CO₂⁺ being larger than the moon radius, a kinetic approach for the ion dynamic is more appropriate than a fluid model and is enable to capture asymmetries in Callisto’s plasma interaction. Therefore, these simulations use the LatHyS hybrid multi-species parallel 3D model [Modolo et al., 2016; 2018] developed to describe planetary plasma environments. This model has already been used to simulate the interaction between Galilean moons and the Jovian magnetosphere : Ganymede [Leclercq, 2015] and Europa [Baskevitch et al., 2025].

We will present our latest simulation results and compare them with Galileo in-situ observations, in particular with the C23 flyby (closest approach at 1052 km) which was the closest one to the center of the Jovian current sheet.