HR: 10:35h
AN: P52B-02    [Abstracts]
TI: Why Does Saturn's Auroral Oval Not Respond to the Rotating Cam Perturbations?
AU: * Kivelson, M G
EM: mkivelson@igpp.ucla.edu
AF: Inst. Of Geophys. and Planetary Phys., 6843 Slichter Hall, 405 Hilgard Ave., Los Angeles, CA 90095-1567, United States
AU: Southwood, D J
EM: david.southwood@esa.int
AF: European Space Agency, HQ, 8-10 Rue Mario-Nikis, Paris, FRA 75015,
AU: Southwood, D J
EM: david.southwood@esa.int
AF: Physics Department, Imperial College, London, SW7 2BZ, United Kingdom
AB: The regular magnetic perturbations in Saturn's magnetosphere have been shown to require source currents flowing in regions external to the planet. The perturbations are also consistent with a rotating source where the current varies with azimuth around the planet as cos φ. From the low latitude data, one deduces that the current seems to cross the equatorial plane and flow from ionosphere to ionosphere on magnetic L-shells in the region 10 to 15. Near the equator, such a current system produces roughly the same perturbations as one with the same azimuthal symmetry flowing on the surface of a sphere of radius 10 to 15 RS, implying that inside the current-carrying shell the perturbation field is uniform and that outside it has the form of an equatorial dipole. Indeed, beyond L=15, but near the equator, the field corresponds approximately to that of an internal dipole tilted by roughly 10 degrees and modified by local plasma contributions. At high latitudes, the spherical model is not applicable and so deductions based on it cannot be made. Evidence for this is seen in the response of the auroral emissions to planetary rotation. Auroral emissions associated with a tilted dipole, as at Earth, move relative to the spin axis as the planetary dipole rotates. At Saturn the auroral emissions move little relative to the spin axis as the planet rotates. The lack of response to the cam currents at high latitudes can be understood by considering current paths in the polar regions, as we shall discuss in this talk.
DE: 2756 Planetary magnetospheres (5443, 5737, 6033)
DE: 5719 Interactions with particles and fields
DE: 5737 Magnetospheres (2756)
DE: 6270 Pluto and satellites
DE: 6280 Saturnian satellites
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting