The Magnetohydrodynamics of Liquid Metal Tornadoes (MAGNADO)

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The self-excitation of large-scale magnetic fields through fluid motion in the metallic interiors of planets is one of the most challenging problems in fluid dynamics. This so-called dynamo process is powered by turbulent rotating convection and involves a complex feedback cycle between the flow and the induced electrical currents. Because planetary dynamos are inaccessible to direct observation and numerical simulations cannot reach the extreme conditions prevailing deep inside planets, we need strongly theoretical-physics driven approaches to elucidate the underlying flow mechanisms and make meaningful and accurate predictions. The aim of the research proposed here is to study rotating magnetoconvection with the novel inclusion of centrifugal buoyancy. Centrifugal buoyancy promotes the formation of large-scale tornado-like vortices. I hypothesise that these tornadoes are favourable for dynamo action: Their inherent nature is helical, breaks mirror-symmetry, thus, resembling the classical theoretical Ponomarenko dynamo model. Additionally, flow speeds well above the free-fall limit can be generated. Direct numerical simulations (DNS) in liquid metals will be central for finding the sweet spot for tornado formation and dynamo action. But pushing the parameters to an extreme is not the solution for this endeavour. Instead, an understanding of the interconnected nonlinear dynamics of these highly turbulent thermal-inertial magnetohydrodynamic flows is required. To this end, successively more complex forms of the induction equation will be considered. Corresponding DNS and experiments in liquid gallium and sulfuric acid will provide a detailed picture of the local planetary induction and dynamo processes. The project shall culminate in an accurate forward model of an analogous convection-driven fluid dynamo device that is also realisable on a laboratory scale, which was previously thought impossible.