Session 2: Solar, Planetary and Space Physics

Title: Exploring Saturn's magnetosphere with Cassini-Huygens
Author(s):   M. Blanc    Main Session Speaker  
Contact: Dr M.Blanc, Observatoire Astronomique De Marseille, France

During the period from the summer of 2004 to late 2008 or later, the Cassini spacecraft will conduct an extendive study of Saturn, its main moon Titan, its icy satellites, rings, atmosphere and internal structure. The spacecraft carries what is probably the most comprehensive and efficient payload for the study of a magnetosphere, its plasmas and fields ever flown to a planet other than Earth. We shall show why this mission offers a unique opprotunity to explore in great detail two very different types of magnetospheres : the intrinsic magnetosphere of Saturn and the "induced" magnetosphere of Titan. . Saturn's intrinsic magnetosphere is particularly interesting because it interacts, via a variety of processes, with all other components of the Saturn system : it interacts with Saturn's ionosphere and upper atmosphere over a broad range of latitudes, and also with the rings (via electrodynamic processes which are likely to produce the ring spokes and to contribute to their dynamics and partly to their long-term evolution), with the icy satellites (via particle bombardment, absorption and sputtering), with the Titan neutral and ion torus and finally with the solar wind. All these interactions contribute sources and sinks of plasma and energetic particles to Saturn's magnetosphere which are balanced globally with additional radial transport. Titan's induced magnetosphere is a plasma cavity dug into Saturn's magnetospheric flow (or at times into the solar wind itself) by the satellite's relative motion. This poorly known object corresponds to a very interesting case of interaction of a plasma flow with an unmagnetized atmospheric obstacle. It is also the main source of plasma in the outer magnetopsphere of Saturn, and superimposes its effects in a very intricate way to those of the solar wind interaction, as shown by recent numerical simulations. We shall describe the Cassini tour and instrument complement, and suggest some of the investigations which can be conducted with this fascinating mission.