Instabilities of Taylor columns in a rotating stratified fluid

We numerically solve for the flow in a differentially rotating spherical shell, with a stable stratification imposed along the rotation axis. The axisymmetric basic state evolves from a Stewartson layer in the unstratified limit to a Taylor column in the strongly stratified limit. For the Taylor columns, we next compute the linear onset of non-axisymmetric instabilities, and show that small (0.1) and large (10) Prandtl numbers yield very different results. For Pr=10, positive and negative differential rotations also yield fundamentally different instabilities.