The plasma environments of Saturn’s moons Enceladus and Rhea

One of the most fascinating discoveries of the Cassini mission was the plume of water vapor and dust below the small moon Enceladus. The interaction between this plume and Saturn’s magnetospheric plasma by means of charge exchange and pickup of newly born ions leads to large-scale perturbation of Saturn’s magnetic field, the Alfven wing. In this thesis, analytical models as well as simulations with the hybrid code A. I. K. E. F. (Adaptive Ion-Kinetic Electron-Fluid) are applied to study the processes that generate these field perturbations. The results are compared with Cassini Magnetometer (MAG) data obtained during the 20 Enceladus flybys, which took place between 2005 and 2013. It is shown that electron absorption by dust leads to a reversal of the Hall current, which is referred to as the ”Anti-Hall effect”. The resulting twist of the magnetic field has been observed during all Enceladus flybys so far. In a second study, the plasma simulations are combined with simulations of the 3D profile of the plume. Thereby, the effect of the distorted electromagnetic fields on the charged dust grains is considered. It is demonstrated that the magnetic field signatures indicate the pick-up of nanograins. In addition, magnetic field observations from the polar R2 and R3 flybys of Saturn’s largest icy moon Rhea are analyzed. Observations of exospheric neutral gas suggest Rhea to be embedded in a tenuous gas envelope. However, the interaction of this gas with the magnetospheric plasma does not cause any measurable contribution to the magnetic field draping pattern detected above the poles of the moon. Instead, it is shown that the finite length of Rhea’s wake leads to a diamagnetic current that generates a weak Alfven wing which has been measured by the Cassini.