Finite Larmor-radius theory of magnetic island evolution

In this paper, we present the first kinetic analysis of nonlinear magnetic island evolution that includes the effect of the excitation of drift waves and extends over the complete range of frequencies comparable to the drift frequency. Our analysis brings to light three new phenomena that have important implications for our understanding of island dynamics. We find that first, the emission of drift waves leads to a radiative torque on the island. Second, the island interacts resonantly with the drift wave it excites when its width is a multiple of the radial wavelength of this drift wave. Third, there exist two bands of frequency where the polarization drift is stabilizing: the first extending from the ion diamagnetic frequency almost to the electric drift frequency, and the second extending from the electron drift frequency towards the electric drift frequency by an amount that varies inversely with the ratio of the island width to the ion gyroradius / SIGLE / Available from British Library Document Supply Centre-DSC:9091.900(UKAEA FUS 463) / BLDSC - British Library Document Supply Centre / GB / United Kingdom