HR: 08:15h
AN: P51D-02 INVITED    [Abstracts]
TI: Saturn's ring ionosphere
AU: * Coates, A J
EM: ajc@mssl.ucl.ac.uk
AF: Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, RH5 6NT, United Kingdom
AB: The arrival of Cassini at Saturn on 1 July 2004 included a spectacular trajectory close to Saturn's rings. This allowed the first direct measurements of the ring ionosphere of Saturn, long postulated but somewhat controversial, and never measured in-situ before. This confirmed the existence of an atmosphere and ionosphere of the rings, and there were several surprising results. First, the atmosphere and ionosphere appears to be dominated by molecular oxygen – so Saturn's rings join Europa and Earth as having a molecular oxygen component to the atmosphere. Second, photoelectrons from the far side of the rings were attenuated by regions of higher optical density in the rings leading to a remarkable anticorrelation between electron fluxes and ring images. In addition, electron spectra contained photoelectrons from the ring ionosphere. Third, it has recently been postulated that currents driven by Saturn lightning may play a role in producing ring spokes. In this paper we review the relevant results from Cassini measurements, and current theory and ideas on production and loss processes. We present our current understanding of this remarkable phenomenon.
DE: 5737 Magnetospheres (2756)
DE: 5759 Rings and dust
DE: 6265 Planetary rings
DE: 6275 Saturn
DE: 7849 Plasma interactions with dust and aerosols (2461)
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting