Modeling Saturn’s Magnetospheric Field

Abstract:

The Cassini spacecraft has now provided an excellent coverage of radial distances, local times and latitudes in Saturn’s magnetosphere. The magnetic field observations from Cassini continue to provide deep insights on the structure and dynamics of Saturn’s magnetosphere. Two of the unexpected findings from Saturn’s magnetosphere are that the current sheet of Saturn assumes a shallow saucer like shape from the forcing of the solar wind on the magnetosphere and that rotational diurnal periodicities are ubiquitous in a magnetosphere formed by an axisymmetric internal field from Saturn.

We have used the comprehensive magnetic field data from Cassini to construct a versatile new model of Saturn’s magnetospheric field for use in current and future data analysis. Our model consists of fully shielded modules that specify the internal spherical harmonic field of Saturn, the ring current and the magnetotail current systems and the interconnection magnetic field from the solar wind IMF. The tilt and hinging of the current sheet is introduced by using the general deformation technique [Tsyganenko, 1998].

In the new model, Saturn’s current sheet field is based on Tsyganenko and Peredo [1994] formalism for disk-shaped current sheets. The shielding field from the magnetopause for the equatorial current sheet and the internal field is specified by Cartesian and cylindrical harmonics, respectively. To derive the shielding fields we use a model of the magnetopause constructed from magnetopause crossings observed by both Cassini and Voyager (Arridge et al. 2006). The model uses observations from Pioneer, Voyager and Cassini. A comparison of model field with the observations will be presented.

Finally, we discuss both the applications of the new model and its further generalization using data from the proximal orbit phase of Cassini.