Role of kinetic effects on the polarization current around a magnetic island.
The polarization current due to a magnetic island rotating in a tokamak plasma is believed to play a central role in the initial evolution of the neoclassical tearing mode. Monte Carlo delta f simulations are performed which also cover a parameter range that is not amenable to analytic treatment but is relevant to experiments. It is shown that the polarization current can change sign when the island rotation frequency is of the order of the ion parallel streaming around the island. Moreover, the current is reduced when the island width is of the order of the ion banana width. Finally, the transition to the enhanced high-collisionality regime is shown to occur for collision frequencies higher than those typical of today's experiments.
Poli
E
E
Max-Planck-Institut für Plasmaphysik, Boltzmannstrasse 2, D-85748 Garching bei München, Germany.
Bergmann
A
A
Peeters
A G
AG