Magnetohydrodynamic "cat eyes" and stabilizing effects of plasma flow

TL;DR

This paper extends hydrodynamic vortex solutions to magnetohydrodynamics, showing how plasma flow and magnetic fields influence vortex stability and pressure structures, with implications for fusion plasma stability.

Contribution

It introduces a generalized MHD vortex solution with flow and magnetic fields, demonstrating their stabilizing effects on pressure islands and vortex stability in plasma.

Findings

Flow and magnetic fields create pressure islands within vortices.

Magnetic-field-aligned flow stabilizes pressure islands.

External magnetic fields enhance vortex stability.

Abstract

The cat-eyes steady state solution in the framework of hydrodynamics describing an infinite row of identical vortices is extended to the magnetohydrodynamic equilibrium equation with incompressible flow of arbitrary direction. The extended solution covers a variety of equilibria including one- and two-dimensional generalized force-free and Harris-sheet configurations which are preferable from those usually employed as initial states in reconnection studies. Although the vortex shape is not affected by the magnetic field, the flow in conjunction with the equilibrium nonlinearity has a strong impact on isobaric surfaces by forming pressure islands located within the cat-eyes vortices. More importantly, a magnetic-field-aligned flow of experimental fusion relevance and the flow shear have significant stabilizing effects in the region of pressure islands. The stable region is enhanced by an external axial ("toroidal") magnetic field.