Breakdown of a magnetohydrodynamic flow structure

Abstract

The breakdown of a swirling blob of fluid subject to a magnetic field parallel to its axis is investigated experimentally in the present work. A flow structure in an electrically conducting fluid always tends to elongate in the direction of a strong, external magnetic field. However, if the magnetic field is sufficiently weak, the poloidal recirculation that is created at the expense of the swirl flow is not damped fast enough. While a vortex may diffuse weakly along the magnetic-field lines, it begins to propagate radially outward in the form of a ring. The transition from a purely diffusive regime to a centrifugally unstable regime has been observed in the present study.