High-wavenumber ballooning-like modes with a finite parallel flow in LHD

摘要

Fully three-dimensional, compressible and nonlinear MHD simulations are carried out to study nonlinear evolution of ballooning-like modes in LHD. A near-ideal dynamical evolution shows that growths of ballooning modes in brings about drastic deformations of the pressure. Another simulation which starts under a finite-amplitude flow parallel to the magnetic field lines suggests that the ballooning modes, which are obtained by the near-ideal simulation, are not sensitive to the parallel perturbation. In the nonlinear stage, only the parallel component of the velocity with n = 1 wavenumber survives the nonlinear saturation and the perpendicular velocity components become less energetic. Consequently, the saturated profile of the simulation with flow becomes more organized than that in the simulation without flow