Progress on the Three-Meter Model of Earth’s Core this (Strange) Year: New Hope for Dynamos with Inner Sphere Roughness.

Abstract:

The dynamo generation of magnetic fields in turbulent flows of conducting fluids and plasmas is an important feature of stars and planetary cores. Our Three-Meter diameter spherical Couette experiment uses liquid sodium to mimic some of the dynamics of these flows, giving insight into these natural phenomena. We are now progressing from the previous amplified magnetic fields toward a possible dynamo state based on adding baffles to the inner sphere. This is an ambitious goal that involves draining 12 tons of sodium to a storage tank, modifying the inner sphere, refilling, and implementing diagnostic instrumentation changes. Numerical studies of Finke and Tilgner (Phys. Rev. E, 86:016310, 2012) suggest roughening the inner sphere, which can be achieved by adding baffles on the inner sphere, result in a reduction in the threshold for dynamo action by increasing the poloidal flows with respect to the zonal flows and ultimately increase helicity. We are working toward a new baffle design that improves the likelihood of observing dynamo action by breaking the symmetry in parameter space of the experiment and generating flows of different topology. Here we present the delayed but in-progress experimental modifications, in spite of a global pandemic and campus shutdowns.