Abstract

The Cassini mission yielded a treasure trove of information on Saturn's largest moon Titan. With many flybys of this complex moon Cassini revealed many aspects of Titan's upper atmosphere and interaction with Saturn's magnetosphere. In many ways Cassini revealed that this moon is unique in that it sustains a dense atmosphere and ionosphere even without the protection of an internal magnetic field. Key to the understanding of this ionosphere is understanding the ion dynamics of Titan's upper atmosphere, namely how these ions are created and lost either to the lower atmosphere where they fall and can contribute to the creation of the complex hydrocarbons seen at the surface or are carried away with Saturn's rapidly flowing magnetospheric particles. Here we present novel measurements of the velocities of many ion species in Titan's upper atmosphere. We show that multiple processes must be responsible for the acceleration of these ions as there is evidence for both mass dependent and independent acceleration. We also show that heavy, relatively complex molecular ions are accelerated and carried into the magnetospheric flow. These ions could contribute to mass loading processes and possibly additional changes in the magnetosphere when Titan resides in Saturn's magnetotail.