Back reaction of magnetic field on rotating convection in presence of thermal heterogeneity

The geomagnetic field is generated and self-sustained by dynamo action in the Earth's liquid outer core. The dynamo is driven by thermo-chemical convection that derives energy from the secular cooling and inner core growth. In addition, the geodynamo is controlled by thermally inhomogeneous core-mantle boundary (CMB). The CMB controls the heat transfer from the core to the mantle. Such heterogeneous CMB heat flux affects the flow and magnetic field patterns generated by the dynamo. The present study investigates the back reaction of magnetic fields on the onset of convective instability inside the inner core tangent cylinder by incorporating various laterally varying thermal structures at the top plate of a plane layer convection model. Different orientations of imposed magnetic fields of various strengths have been implemented at various rotation rates. Consequently, localised convective flow clusters have been developed in the regions of heat flow higher than the mean heat flux as a consequence of imposed laterally heterogeneous thermal structures. Additionally, convective clusters have developed with both odd and even orders of thermal heterogeneity, resulting in laterally asymmetric and symmetric structures respectively. As a result of rapid rotation, small-scale columnar rolls are formed in a weak magnetic field, regardless of the magnetic field orientation. However, under a strong magnetic field with a horizontally imposed magnetic field, large-scale convection rolls are developed.