Order and disorder in planetary dynamos : summer study program in geophysical fluid dynamics

Abstract

Our principal lecturer, Stephen Childress, can be seen emerging from the "magnetic cottage" he constructed to edify those of us who attended G.F.D. '87. His central theme was the kinematic properties of the "fast" dynamo, one whose growth rate is insensitive to electrical conductivity. These novel studies, and the seminars given by Andrew Soward and others, offer assurance of more mechanistic understanding of evolving magnetic fields in stars and planets. The timely juxtaposition of Childress' lectures on kinematic fast dynamos and the seminars by Bruce Bayly on inertial three-dimensional instabilities of shear flow, may lead soon to a dynamic fast-fast dynamo. Faster than convecting continents, slower than Antarctic bottom water, waves in the Earth's magnetic field move to the west. Geophysicists' knowledge of the underlying process appears to advance at a similar pace. Yet the dynamos of the summer season already have suggested hydromagnetic flows which offer hope both of realizeable laboratory dynamos and more realistic planetary models. Perhaps the pace of testable predictions will quicken?