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. Observed non-axisymmetric structure in the Earth’s magnetic field over long timescales almost certainly arises due to the influence on heterogeneous boundary conditions imposed at the either the top or bottom of the fluid layer. Although considerable previous work has considered the influence on core convection of heterogeneous heat flux conditions imposed at the top boundary, relatively little work has been done investigating heterogeneous boundary conditions applied at the bottom boundary, either in isolation or simultaneously with heterogeneous conditions on the top boundary. Initial simulations of both non-magnetic convection and the geodynamo indicate that the inclusion of heterogeneous boundary conditions at the 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 investigate both the general principles of how heterogeneous boundary conditions influence the dynamics of convection within a rotating fluid shell, and the potential of such boundary conditions to explain the non-axisymmetric components of the Earth’s magnetic field.