Energy distribution in nonaxisymmetric magnetic Taylor-Couette flow

TL;DR

This study investigates energy distribution in nonaxisymmetric magnetic Taylor-Couette flow, revealing how magnetic instabilities generate and transfer energy between modes, with implications for controlling flow patterns.

Contribution

It demonstrates the coexistence and energy transfer between axisymmetric and nonaxisymmetric modes in magnetic Taylor-Couette flow through nonlinear simulations.

Findings

Both m=1 and axisymmetric modes appear in simulations.

Energy can be transported into the axisymmetric field via inverse cascade.

Mode ratio can be controlled by Reynolds and Hartmann numbers.

Abstract

Azimuthal magnetorotational instability is a mechanism that generates nonaxisymmetric field pattern. Nonlinear simulations in an infinite Taylor-Couette system with current-free external field show, that not only the linearly unstable mode m=1 appears, but also an inverse cascade transporting energy into the axisymmetric field is possible. By varying the Reynolds number of the flow and the Hartmann number for the magnetic field, we find that the ratio between axisymmetric (m=0) and dominating nonaxisymmetric mode (m=1) can be nearly free chosen. On the surface of the outer cylinder this mode distribution appears similarly, but with weaker axisymmetric fields. We do not find significant differences in the case that a constant current within the flow is added.