Nonlinear Growth of a Single Neoclassical MHD Tearing Mode in a Tokamak

摘要

The nonlinear evolution equation for the growth of a single neoclassical MHD tearing mode is derived from the usual resistive MHD equations with neoclassical effects included. For the case delta ' > 0 where the usual resistive MHD modes are unstable, in nonlinear neoclassical MHD there is an intermediate time regime in which the island width w grows only as t/sup 1/2/. However, eventually the neoclassical MHD tearing modes are found to enter the usual resistive MHD Rutherford regime where w infinity t. Physically, the neoclassical MHD bootstrap current effects modify the linear and early nonlinear growth of tearing modes. However, eventually the magnetic islands flatten the pressure gradient within the island to remove these effects and return, at long times, to the usual quasilinear picture for the nonlinear evolution of a single resistive MHD tearing mode. (ERA citation 11:028992)