Nonlinear simulation of resistive ballooning modes in the Large Helical Device

Abstract

Nonlinear simulations of a magnetohydrodynamic (MHD) plasma in full three-dimensional geometry of the Large Helical Device (LHD) [O. Motojima et al., Phys. Plasmas 6, 1843 (1999)] are conducted. A series of simulations shows growth of resistive ballooning instability, for which the growth rate is seen to be proportional to the one-third power of the resistivity. Nonlinear saturation of the excited mode and its slow decay are observed. Distinct ridge/valley structures in the pressure are formed in the course of the nonlinear evolution. The compressibility and the viscous heating, as well as the thermal conduction, are shown to be crucial to suppress the pressure deformations. Indication of a pressure-driven relaxation phenomenon that leads to an equilibrium with broader pressure profile is observed. © 2001 American Institute of Physics.