Novel features of the rapid growth and the nonlinear dynamics of driven magnetic islands in rotating plasmas are studied by nonlinear magnetohydrodynamics simulations. The transition phase of the magnetic island evolution is found between the rapid growth phase and the Rutherford-like phase in the low resistivity regime. It is shown that the rapid growth of the magnetic island is associated with its deformation that leads to the secondary magnetic island formation around the original X-points. The suppressed state is characterized by the asymmetric deformation of the magnetic island caused by the non-monotonic torque profile within the island separatrix. In the regime of the high magnetic flux input rate, the critical magnetic island width shows weak dependence on viscosity while it noticeably depends on resistivity. It is conjectured that this is a result of the effect of the Alfven type interaction between the rotating plasma and the fast growing external magnetic perturbation.
Experiment of magnetic island formation in Large Helical Device