From small-scale to large-scale dynamos driven by rotating convection

Astronomy Unit Seminars
Dr Benjamin Favier (University of Cambridge)
March 15th, 2013 at 14:30
GO Jones UG1

One of the most important aspect of dynamo theory is to explain the existence of large-scale coherent magnetic fields in planets and stars. In most rotating bodies, differential rotation provides an obvious way to generate toroidal from poloidal magnetic field, the so-called Omega effect. The remaining step to close the dynamo loop is however more controversial. It is common to invoke the alpha effect which arises from correlations in small-scale fluctuations and is responsible for the generation of a large-scale electromotive force. We discuss here the generation of such large-scale magnetic fields by rotating convection using a local approach. From small-scale to large-scale dynamos and from simple steady flows to the fully turbulent regimes, we discuss different aspects of this problem and its relation to recent global spherical simulations of stellar and planetary dynamos.