Towards realistic models of magnetic field generation in planetary cores

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Convection-driven flows influenced by rotation are ubiquitous in planetary interiors, including the liquid cores of terrestrial bodies, the outer regions of gas giants and the convective regions of cool stars. These flows generate global-scale magnetic fields that can be observed remotely and hence provide unique insight into otherwise inaccessible regions of planets and stars. However, from a fluid dynamical perspective, modelling the rotating fluid dynamics in the deep fluid interiors of these bodies represents an outstanding challenge because of the rapid rotation rates (equivalent to Ekman numbers E < 10-10) and turbulent flow (Reynolds number Re > 108). Such extreme conditions cannot be modelled by direct 3D computer simulation and so complementary approaches are required. This project will combine theoretical and computational work to improve: 1) quasi-geostrophic (QG) models of core dynamics that exploit the rapidly rotating limit to reduce the (magneto)hydrodynamic equations to 2D; 2) an asymptotically reduced model of convection and magnetic field generation that is valid in the limit of rapid rotation. Systematic analysis and comparisons of these new models with existing 3D simulations and convection experiments conducted at UCLA will allow the turbulent dynamics and the role of magnetic fields to be analysed in hitherto inaccessible dynamical regimes with direct application to planetary interiors.