Nonlinear Simulation of Edge-Localized Mode in Spherical Tokamak

Numerical simulation which is based on the nonlinear resistive magnetohydrodynamic(MHD) model is executed to reveal the dynamics of the edge-localized modes(ELMs) in the spherical tokamak(ST) plasma. Characteristic features of the ELMs, such as the formation of the filaments, the toroidal localization of the mode structures, and the separation of plasmoid from the bulk, have been successfully reproduced. These processes are found to be the consequence of the nonlinear growth of the ballooning mode under the MHD assumptions. The simulation results are compared with the experimental observations in Mega-Amp Spherical Tokamak(MAST), and show good agreement.