Saturn Magnetospheric Interaction with Titan Ionisation Sources and Dynamics as Inferred from Cassini Observations

ÅGREN, K.; WAHLUND, J.; MODOLO, R.; MOROOKA, M. W.; LUMMERZHEIM, D.; BERTUCCI, C.; GALAND, M.; MÜLLER-WODARG, I.; COATES, A.; LEWIS, G.; CANU, P.; KURTH, W. S.; NEUBAUER, F. M.; CRAVENS, T.; WAITE, J. H., JR.; YELLE, R.; YOUNG, D.

Congreso; AGU Fall Meeting 2006; 2006

We present results of the cold plasma environment around Titan obtained during several Titan flybys primarily from the Cassini Radio and Plasma Waves Science (RPWS) Langmuir probe (LP) sensor. It shows that the magnetosphere of Saturn interacts strongly with this moon's ionosphere and exo-ionosphere. The altitude structure of the deep ionosphere during nightside conditions was found to be reproducible by a simple electron impact ionisation model. The dense and cold exo-ionosphere (from the exobase at 1430 km outward to several Titan radii from the surface), although partly affected by exospheric ionisation of impacting low energy electrons (30-50 eV), is dominated by induced magnetospheric forcing. The magnetospheric flow also seems to force a complicated dynamic situation below the exobase. The exo-ionosphere acts as a heavy mass- loading region for the magnetospheric flow resulting in draping of the magnetic field within Titan's induced magnetosphere. We illustrate the importance of UV ionisation on the sunlit side of Titan for the exo- ionospheric escape from this moon.