The exosphere of Titan and its interaction with the kronian magnetosphere: MIMI observations and modeling

Titan's nitrogen-rich atmosphere is directly bombarded by energetic ions, due to its lack of a significant intrinsic magnetic field. Singly charged energetic ions from Saturn magnetosphere undergo charge exchange collisions with neutral atoms in Titan's exosphere, being transformed into energetic neutral atoms (ENAs). The ion and neutral camera (INCA), one of the three sensors that comprise the magnetosphere imaging instrument on the Cassini/Huygens mission to Saturn and Titan, images the ENA emissions from various ion/gas interaction regions in the Saturnian magnetosphere. During Cassinis second orbit around Saturn the spacecraft performed the Ta Titan flyby (26 October 2004), at an altitude of only 1174 km. INCA data acquired during this targeted close flyby not only confirm model predictions of dominant finite ion gyroradii effects, but also reveal a much more complex interaction. These observations are analyzed and compared to simulations. A new Titan exosphere model is then proposed.