Four-frequency solution in a magnetohydrodynamic Couette flow as a consequence of azimuthal symmetry breaking

TL;DR

This paper investigates how azimuthal symmetry breaking in magnetohydrodynamic Couette flows leads to complex quasiperiodic states with four fundamental frequencies, revealing a sequence of bifurcations influenced by magnetic field strength and differential rotation.

Contribution

It identifies a novel bifurcation pathway resulting in four-frequency quasiperiodic flows due to azimuthal symmetry breaking in MHD Couette flows.

Findings

Four-frequency quasiperiodic flows arise from symmetry-breaking bifurcations.

Bifurcation sequence includes transitions from symmetric to asymmetric states.

Flow states depend on magnetic field strength and differential rotation levels.

Abstract

The occurrence of magnetohydrodynamic (MHD) quasiperiodic flows with four fundamental frequencies in differentially rotating spherical geometry is understood in terms of a sequence of bifurcations breaking the azimuthal symmetry of the flow as the applied magnetic field strength is varied. These flows originate from unstable periodic and quasiperiodic states with broken equatorial symmetry but having four-fold azimuthal symmetry. A posterior bifurcation gives rise to two-fold symmetric quasiperiodic states, with three fundamental frequencies, and a further bifurcation to a four-frequency quasiperiodic state which has lost all the spatial symmetries. This bifurcation scenario may be favoured when differential rotation is increased and periodic flows with $m$-fold azimuthal symmetry, $m$ being product of several prime numbers, emerge at sufficiently large magnetic field.