Boundary Controls on Convection from the Top and Bottom of Earth's Fluid Core

Convection within the Earth’s fluid core generates the planetary magnetic field; spatial and temporal variations of the geomagnetic field can thus be used to gain insight into the dynamics of this otherwise inaccessible region. Seismic, geomagnetic, and geodynamic observations indicate that lateral variations in heat flow are imposed on the core at the top, and possibly bottom, boundary. These forcings, together with free convection, produce a rich variety of dynamical behaviour. Accessing the Earth-like regime of rapid rotation (i.e. low Ekman number), strong driving (i.e. high Rayleigh number), and vigorous turbulence (i.e. high Reynolds number) in a spherical shell is computationally challenging. Initial non-magnetic simulations by the group in Leeds indicate that the inclusion of heterogeneous boundary conditions at the top and bottom of the fluid core can significantly reorganise the pattern of convection, resulting in novel scaling relations for the transport of heat through the system. This project will produce a systematic study of the influence of boundary control on the dynamics of non-magnetic convection within a rotating fluid shell at the most Earth-like conditions achieved to date and investigate the potential for these dynamics to explain observed features of the Earth’s magnetic field.