Titan's Interaction With the Supersonic Solar Wind During T96: A Hybrid Simulation Study

Abstract:

We apply a hybrid simulation code (kinetic ions, fluid electrons) to study the structure of Titan’s plasma environment during the T96 flyby on 01 December 2013. The T96 encounter constitutes the only event of the Cassini era during which Titan was exposed to the supersonic solar wind upstream of Saturn’s bow shock. Cassini plasma and magnetic field observations revealed a Venus/Mars-like plasma interaction, including the formation of a bow shock and a magnetic barrier upstream of Titan. However, it has also been suggested that the ambient solar wind conditions were not stationary at the time of the T96 encounter: around closest approach Cassini probably passed through a region of fossilized magnetic fields, arising from Titan’s interaction with a previously encountered, high-pressure solar wind regime. To substantiate this hypothesis, we carry out simulation runs for different ram pressures of the incident solar wind. The model reveals the interaction region to be dominated by kinetic effects, such as a splitting of the bow shock due to large ion gyroradii (shocklets). The simulation results are compared against Cassini magnetic field data from T96.