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S. V. Mirnov, I. Semenov, A. M. Belov,
E. A. Azizov
State Research Center TRINITI, Troitsk, 142092 Moscow Region, Russian Federation
Abstract. A situation in tokamaks is analyzed in which the development of
strong plasma current filamentation leads to nonlinear magnetic islands
formation near resonant magnetic surfaces. It is shown that, along with the
usual ``negative'' magnetic islands, in which the modulation of the
perturbation currents is negative, ``positive'' islands can form in local
regions with the positive current modulation. The ``positive'' magnetic
islands can be a reason of the ``hot spot'' in plasma center during sawtooth
crash. Also the ``positive'' islands, probably, plays the important role in
m=2 development during the major disruption and in the locked modes dynamics.
IAEA 2001
