Effects of a toroidal rotation on the stability boundary of the MHD modes in the Tokamak edge pedestal

Effects of a toroidal rotation on the stability of the MHD modes in the edge pedestal, which relate to the edge-localized mode (ELM), are investigated numerically. The new linear MHD initial value code MINERVA is developed for analyzing the effects of a toroidal rotation on the edge MHD stability with high accuracy. As the numerical results, a toroidal rotation increases the achievable maximum pressure gradient. Moreover, it is found for the first time that the edge MHD mode whose toroidal mode number is intermediate (>5) is stabilized, and this stabilization realizes to sustain a steep pressure gradient even in the low edge current density case. From the result in this paper and the previous theoretical studies about the effect of the sheared toroidal rotation on the ballooning mode, the toroidal rotation is thought to stabilize the edge MHD mode due to suppressing the destabilizing contribution from the pressure-driven component of the MHD mode. (author)