Finite Larmor-Radius Theory of Magnetic Island Evolution

Gyrokinetic theory is used to investigate the effect of the polarization drift on magnetic island evolution. Three regimes are found. For island phase velocities between the ion- and electric-drift velocities, the polarization current is shown to be stabilizing. For phase velocities between the electric- and electron-drift velocities, the island emits drift waves. This results in a radiative drag force. For all other phase velocities the polarization current is destabilizing, in agreement with the fluid limit.