SPEARS Seminar: The strange magnetism of Saturn and its magnetospheric dynamics

Professor David Southwood, Imperial College London

Tuesday 12 June 2012, 1600-1700
Cavendish Colloquium Room

Spacecraft had flown past Saturn three times before Cassini arrived in orbit in 2004. The results from the Cassini mission concerning magnetospheric science alone show not only how limited was our understanding of the system from the flybys and previous remote sensing but also provide a picture of a planetary magnetosphere and magnetic field that had confounded any prior prediction.

Indeed, defying our general understanding of the workings of planetary dynamos, the internal planetary field has yet to yield any evidence of departure from rotational symmetry. The long remotely-established radio periodicity now appears to be tied to polar ionospheric rotation (with rates which differ between northern and southern hemispheres!).

The planet does have complex auroral displays which also display rotational modulation. However, unlike Earth, the magnetospheric circulation is almost certainly not solar wind driven but internally driven. In another surprise, the major source of ionised material which drives the magnetospheric dynamics is not the planet-sized moon, Titan, but geysers on the tiny moon, Enceladus, just outside the rings.

Eight years after Cassini's arrival at Saturn, sense is beginning to be made of the complex plasma science of the magnetosphere and the dynamics of the external field. However elucidating the internal magnetism of the planet still awaits the final stages of the Cassini mission as the spacecraft is prepared for a final descent into the atmosphere.