Plasma rotation driven by rotating magnetic fields

Abstract

We report a novel method to control plasma rotation speed, namely, using the rotating magnetic field (RMF), which is a mature technique to form field reversed configuration, to drive the electron rotation and then the ion rotation via electron–ion collisions in a magnetic mirror plasma. It can be observed that the plasma starts rotating if the RMF strength exceeds a threshold value, corresponding to which the value of the magnetization parameter becomes larger than the value of the penetration parameter. The flow speed achieved in this experiment is approximately 0.14 Mach. The rotation is found to start from outside to inside with the propagating time almost equal to the penetration time of the RMFs. Also, a clear sheared flow is observed to have developed in the region of core plasma. It has been further identified that the electron–ion friction is the dominant force to drive the ion spinning up. The rotation speed is primarily determined by the RMF strength, instead of background magnetic field strength, which may offer a method to study the effect of rotation on the confinement in different magnetic field strengths while keeping the rotation profile intact.