Nonlinear Analysis for Stabilization of Interchange Mode in LHD Plasmas

The nonlinear behavior of the interchange mode in Large Helical Device (LHD) plasma depends on the overlap of the vortices with different helicity. If the vortices are separated in the radial direction, each mode saturates mildly with generating the local flat regions in the pressure profile. In the case of significant overlap of the vortices, the appearance of large-scale convection results in sudden global reduction of the pressure. The sequence of the saturated pressure profile in the increase of beta can suppress the overlap. Self-organization of the pressure profile to suppress the overlap of the vortices can be the stabilizing mechanism in the LHD plasma.