A model of the ionosphere of Saturnʹs rings and its implications

The detection of cold O 2 + and O+ ions in the vicinity of Saturnʹs rings during the Cassini Orbiter orbit insertion confirmed expectations that the rings would have a water product atmosphere and ionosphere. These observations prompted a new look at their origin and nature by Johnson et al. [Johnson, R.E., Luhmann, J.G., Tokar, R.L., Bouhram, M., Berthelier, J.J., Sittler, E.C., Cooper, J.F., Hill, T.W., Crary, F.J., Young, D.T., 2006. Icarus 180, 393–402], but also raised questions about the ionosphereʹs spatial distribution and fate that inspired the ionospheric model described in this report. Here a test particle model with some Monte Carlo aspects is used to consider the behavior of the O 2 + and O+ ions produced in the atmosphere of Saturnʹs rings. Key features of these calculations include the Johnson et al. description of the production of the ring atmosphere, and the effects of the offset dipole magnetic field of Saturn. The results suggest that the latter should produce some possibly observable asymmetries in both the inner ring ionosphere and the precipitation of ring ions into the atmosphere of Saturn. Further in situ observations of the rings are not currently planned, but remote sensing instruments on Cassini may provide future observational tests of the model.