Speaker:
Dr Susanne Horn, School of Computing, Electronics and Mathematics, Coventry University
Title:
Probing Planetary Core Turbulence via DNS of Liquid Metal Rotating Magnetoconvection
Abstract:
The metallic fluid in the deep interiors of terrestrial planets is vigorously convecting, and the interplay of this turbulent convective motion with rapid rotation drives the dynamo action and maintains large-scale magnetic fields. Understanding the complex couplings between buoyancy, Lorentz, and Coriolis forces and the exact mechanisms behind the magnetic field generation remains one of the challenges in planetary fluid dynamics. The system of rotating magnetoconvection (RMC), i.e. a fluid heated from below, cooled from above and subjected to rotation and an imposed magnetic field, constitutes an idealised local model of planetary core turbulence, capturing all of the key ingredients.
In this talk, I will present results from direct numerical simulations (DNS) of RMC in a low Prandtl number fluid, as characteristic for liquid metals. In particular, I will discuss how the small Prandtl number gives rise to unique instabilities and affects the dynamics and flow morphologies. By varying the thermal forcing, the magnetic field strength, and the rotation rate, several distinct pathways from the onset of convection to the turbulent state can be followed. Thus, we can explore the individual instabilities, analyse their imprints on the flow, trace their evolution, and also investigate their interactions. We find that the signatures of the underlying instabilities remain present up to relatively high supercriticalities, generally leading to multimodal flows with various prominent temporal and spatial scales. However, it is neither necessarily the onset nor the latest instability setting in that dominates the overall flow.