Modeling of a Giant Planet Magnetodisc

We present preliminary calculations of magnetic flux functions associated with the perturbation of a planetary dipole field by a rotating, equatorially-situated disk of plasma. Such structures are central to the dynamics of the rapidly rotating magnetospheres of Jupiter and Saturn. They are 'fed' internally by sources of plasma from moons such as Io (Jupiter) and Enceladus (Saturn). For these preliminary models, we use a scaled form of Caudal's Euler potentials for the Jovian magnetodisc [G. Caudal, J. Geophys. Res., 1986]. In this formalism, the field is assumed to be azimuthally symmetric about the planet's axis of rotation, and plasma temperature is constant along a field line. We perturb the dipole potential ('homogeneous' solution) by using simplified, corotating, planar disc structures with uniform plasma beta parameter. Our results quantify the degree of radial 'stretching' exerted on the dipolar field lines through the plasma's rotational motion and pressure. We comment on the degree of equatorial confinement as represented by the scale height associated with disk ions of varying mass and temperature. We also make preliminary comparisons with Cassini magnetic field measurements at Saturn.