Strong Nonlinear Effects in the Dynamics of Tearing Modes Controlled by Electron Cyclotron Current Drive

The 2-D time-dependent response of a tearing mode magnetic island to a radio frequency (RF)-driven current may lead to strong nonlinear effects. An extended magnetohydrodynamics model shows first the prompt appearance of current sheets tending to shield the RF current effect and, subsequently, a nonlinear filamentation of the island structure that eventually proceeds in the coalescence of secondary islands.