Titan's ionosphere in the magnetosheath: Cassini RPWS results during the T32 flyby

Abstract. The Cassini mission has provided much information about the Titan environment, with numerous low altitude encounters with the moon being always inside the magnetosphere. The only encounter taking place outside the magnetopause, in the magnetosheath, occurred the 13 June 2007 (T32 flyby). This paper is dedicated to the analysis of the Radio and Plasma Wave investigation data during this specific encounter, in particular with the Langmuir probe, providing a detailed picture of the cold plasma environment and of Titan's ionosphere with these unique plasma conditions. The various pressure terms were also calculated during the flyby. The comparison with the T30 flyby, whose geometry was very similar to the T32 encounter but where Titan was immersed in the kronian magnetosphere, reveals that the evolution of the incident plasma has a significant influence on the structure of the ionosphere, with in particular a change of the exo-ionospheric shape. The electrical conductivities are given along the trajectory of the spacecraft and the discovery of a polar plasma cavity is reported.