Instabilities in magnetized spherical Couette flow

TL;DR

This paper uses 3D numerical simulations to explore flow instabilities in magnetized spherical Couette systems, revealing boundary-driven instabilities similar to MRI and comparing results with experimental data.

Contribution

It introduces detailed numerical analysis of flow instabilities in spherical Couette flow under magnetic fields, highlighting boundary effects and MRI-like phenomena.

Findings

Different layers and jets form depending on parameters.

Boundary instabilities resemble magnetorotational instability.

Simulation results align with Maryland experiment observations.

Abstract

We report 3D numerical simulations of the flow of an electrically conducting fluid in a spherical shell when a magnetic field is applied. Different spherical Couette configurations are investigated, by varying the rotation ratio between the inner and the outer sphere, the geometry of the imposed field, and the magnetic boundary conditions on the inner sphere. Either a Stewartson layer or a Shercliff layer, accompanied by a radial jet, can be generated depending on the rotation speeds and the magnetic field strength, and various non-axisymmetric destabilizations of the flow are observed. We show that instabilities arising from the presence of boundaries present striking similarities with the magnetorotational instability (MRI). To this end, we compare our numerical results to experimental observations of the Maryland experiment, who claimed to observe MRI in a similar setup.