Explosive growth and nonlinear dynamics of the forced magnetic island

Novel features of the explosive growth and the nonlinear dynamics of the forced magnetic island subject of the suppression by plasma rotation are studied by nonlinear MHD simulations. The regime of the explosive growth of the externally driven magnetic island was found. This regime occurs after the plasma rotation has been sufficiently reduced due to the interaction with the external field. It is shown that the explosive growth is associated with changes in the structure of the magnetic island and appearance of the localized plasma current around the X-point. It was found that the presence of the localized plasma current causes the enhanced magnetic reconnection due to the occurance of secondary instabilities of the current sheet. As the result, the long term evolution of the forced magnetic island, such as , e.g., the seed island for the neoclassical tearing modes (NTM), is dominated by the secondary reconnection as the resistivity becomes small.