On the rotation of magnetic islands in a tokamak

We investigate various mechanisms affecting the rotation of magnetic islands. Generally, the rotation of a magnetic island is determined by a $\sin \left[m(\theta -\zeta/q) -\omega t\right] $ component of the non-ambipolar electric current. We consider several processes leading to the transverse non- ambipolar electric currents in a tokamak such as small-scale electromagnetic turbulence, anomalous viscosity, and neoclassical transport. It is argued that in a toroidal plasma the non-ambipolar neoclassical transport is a dominant process. It results in the locking of the magnetic island into the ion poloidal motion.