Experimental observation of response to resonant magnetic perturbation and its hysteresis in LHD

It has been observed that thresholds of the amplitude of resonant magnetic perturbation (RMP) for the healing/growth transition of the magnetic island depend on the magnetic axis position R_ax in the Large Helical Device (LHD). The RMP threshold for growth of the island increases as the magnetic axis position R_ax increases. Furthermore, the threshold of RMP for healing is smaller than that for growth, which means hysteresis in the critical RMP at a healing/growth transition. The poloidal viscosity would be considered as a candidate to explain the experimental observation from the view point of the balance between the electromagnetic torque and the viscous torque. (author)