Titan's Interaction with Saturn's Dynamic Magnetosphere: Three-Dimensional Multi-fluid Simulations

A three-dimensional multi-fluid model of Titan embedded within Saturn's magnetosphere has been developed to determine how the variability of Titan's space environment affects Titan's plasma interaction. Results from simulations with Titan located at 9, 13.6, and 21 Saturn local time (SLT) are presented. At each location, Titan periodically interacts with Saturn's plasma disk. Inside the plasma disk, the plasma flow becomes super-Alfvenic which compresses Titan's induced magnetosphere and enhances ion outflow. In the simulation with Titan at 9 SLT, Titan enters a boundary layer when the magnetopause is less than 2 Saturn radii from Titan. The plasma flow inside the boundary layer is either shearing or out of Titan's orbital plane. When the plasma flow is aligned with Saturn's magnetic field, the field does not drape around Titan's ionosphere and the J&ar;xB&ar; force does not produce an ion tail. In the simulation with Titan at 13.6 SLT, Titan crosses into Saturn's magnetosheath. In the magnetosheath, Titan's induced magnetosphere is irregular and Titan's connection to Saturn's magnetosphere is removed by ionospheric convection in ∼1.5 hours. Titan's ion tail may prevent (or at least slow) Saturn's magnetopause from moving radially inward. Therefore, Titan's ion tail may prevent Titan from crossing Saturn's magnetopause when Titan is in the pre-noon sector of Saturn's magnetosphere.;In addition, a three-dimensional multi-fluid model of Titan's local plasma interaction has been developed and is shown to be in good agreement with magnetic field measurements from Cassini's TA, TB, and T3 flybys. Large asymmetries are simulated as result of ion gyroradius effects. This model has been modified to include neutral fluids, ionization sources, and ion neutral interactions. The ionization rates and resulting ion densities are shown to be in good agreement with existing models of Titan's ionosphere and with data from Cassini. Collisions between Titan's dense neutral atmosphere and Saturn's magnetospheric plasma are shown to increase the altitude of the magnetic pile-up region by ∼500 km.