Stabilization of Z-pinch By Velocity Shear

A numerical experiment is run to assess the stabilization of ideal magnetohydrodynamic (MHD) instabilities by externally applied velocity shear. A Z pinch, unstable to both kink and interchange (sausage) instabilities, is subjected to an external force that drives sheared mass flow along the axis. The turbulence from the MHD instabilities is found to be suppressed significantly with increasing Mach number of the flow. At sonic Mach numbers of 4–5, the “discharge” is seen to have recovered to its laminar state in more than 95% of the volume, there being a small residual wobble at the center of the column. For lower Mach numbers, the wobble becomes more significant. This is consistent with analytic theories that predict supersonic sheared flows are needed to stabilize MHD instability.