Influence of negatively charged plume grains on the structure of Enceladus' Alfvén wings: Hybrid simulations versus Cassini Magnetometer data

Abstract

[1] We apply the hybrid simulation code AIKEF (adaptive ion kinetic electron fluid) to the interaction between Enceladus' plume and Saturn's magnetospheric plasma. For the first time, the influence of the electron-absorbing dust grains in the plume on the plasma structures and magnetic field perturbation, the Alfven wing, is taken into account within the framework of a global simulation. Our work continues the analytical calculations by Simon et al. (2011), who showed that electron absorption within the plume leads to a negative sign of the Hall conductivity. The resulting twist of the magnetic field, referred to as the Anti-Hall effect, has been observed during all targeted Enceladus flybys between 2005 and 2010. We show that (1) applying a plume model that considers both, the neutral gas and the dust allow us to quantitatively explain Cassini Magnetometer (MAG) data, (2) dust enhances the anti-Saturnward deflection of the ions, causing asymmetries which are evident in the MAG data, and (3) the ions in the plume are slowed down below 1 km s−1; and we compare our results to MAG data in order to systematically analyze variations in the plume activity and orientation for selected pairs of similar flybys: (E5, E6), (E7, E9) and (E8, E11).