Nonlinear dynamics of rotating drift-tearing modes in tokamak plasmas

The rotation frequency of the drift-tearing mode is investigated with numerical simulations of reduced two-fluid equations. An extended analytical formula of the rotation frequency of the drift-tearing mode is derived, and is used to analyze numerical results. It is found that the rotation frequency depends strongly on the poloidal zonal flow generated by the drift-tearing mode. The dependence of the rotation frequency on transport coefficients is examined in the nonlinear saturation phase. It is found that ion viscosity μ and parallel resistivity ηparallel play important roles by controlling the self-generated zonal flow through the change of the balance between the Reynolds stress and the Maxwell stress. The dependence of the rotation frequency on the magnetic Prandtl number μ/ηparallel shows a monotonic increase.