Regularized magnetic islands. II. The role of polarization current

The role of polarization current in the problem of rotating magnetic island s in the absence of drift effects is discussed for the case of nonregulariz ed and regularized velocity profiles governed by the perpendicular viscosit y. The polarization current is calculated taking into account the finite io n Larmor radius effects. It is shown that, in correspondence with the gener al rule by Waelbroeck and Fitzpatrick [Phys. Rev. Lett. 78, 1703 (1997)], t his current is destabilizing. The destabilizing contribution of the polariz ation current into the generalized Rutherford equation for the magnetic isl and width does not depend on whether the profile function is regularized or not. It is shown that the Larmor corrections to the current consist of the sum of two oppositely directed currents and do not contribute into the gen eralized Rutherford equation. (C) 2000 American Institute of Physics. [S107 0-664X(00)01604-9].