Linear three-dimensional instability of a magnetically driven flow

The instability of a rotating magnetic field driven liquid metal flow in a finite cylinder with respect to infinitesimal azimuthally periodic
perturbations is studied numerically. This instability is observed to set in prior to its axisymmetric counterpart with relatively low frequency at diameter-to-height ratios between 0.5 and 2. The both, axisymmetric and three-dimensional instabilities have similar characteristic features. The instability originates in the cross-section of the horizontal and vertical rotating boundary layers and excites inertial waves in the inviscid core.