Composition and Dynamics of Plasma in Saturn's Magnetosphere
Lewis, G. R.; Coates, A. J.; Linder, D. R.; Grande, M.; Thomsen, M. F.; Tokar, R. L.; Johnson, R. E.; McAndrews, H. J.; Holmlund, C.; Sittler, E. C.; Smith, H. T.; McComas, D. J.; Young, D. T.; Bolton, S.; Reisenfeld, D.; Vilppola, J.; Dunlop, M. W.; Goldstein, R.; Berthelier, J. -J.; Gosling, J. T.; Burch, J. L.; Hill, T. W.; Mursula, K.; Crary, F. J.; Illiano, J. -M.; Baragiola, R. A.; Bebesi, Z.; Pallier, E.; Rymer, A. M.; Gilbert, L. K.; Tanskanen, P.; Narheim, B. T.; Maurice, S.; Blanc, M.; Barraclough, B. L.; Svenes, K. R.; Szegö, K.; Kelha, V.; Bakshi, S.; Delapp, D.; Furman, J. D.; Zinsmeyer, C.; Glenn, D.
United States, France, United Kingdom, Finland, Norway, Hungary
Abstract
During Cassini's initial orbit, we observed a dynamic magnetosphere composed primarily of a complex mixture of water-derived atomic and molecular ions. We have identified four distinct regions characterized by differences in both bulk plasma properties and ion composition. Protons are the dominant species outside about 9 RS (where RS is the radial distance from the center of Saturn), whereas inside, the plasma consists primarily of a corotating comet-like mix of water-derived ions with ~3% N+. Over the A and B rings, we found an ionosphere in which O2+ and O+ are dominant, which suggests the possible existence of a layer of O2 gas similar to the atmospheres of Europa and Ganymede.