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Abstract

Stable stratified layer near CMB plays a significant role both on the flow pattern in the outer core, as well as the morphology of the geomagnetic field. Using a radially varying heat source various temperature profiles have been generated. These profiles are characterised based on the presence of a stable stratified layer, of varying thickness, near the outer boundary. The dynamics of the Earth’s outer core convection is the central focus of this study. Heat flux variation at the outer boundary, with three different amplitudes of spherical harmonic pattern, is imposed to mimic core-mantle thermal interactions. The flow structures are analysed based on the vorticity dynamics and the role of helical flow structures, responsible for dynamo action and generating magnetic fields. It is observed that although the anticyclonic helicity is dominant over the cyclonic helicity, positive heat flux promotes the cyclonic helicity whereas the negative heat flux promotes the anticyclonic helicity in strongly driven convection. In rapidly rotating regime, thicker stratified layer tries to damp the magnetic field across the layer resulting in a large scale field at the CMB. Finally, it is also seen that high heat flux boundary forcing causes the dynamo action to fail.