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 mu and parallel resistivity eta(parallel to) 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 mu/eta(parallel to) shows a monotonic increase. (c) 2008 American Institute of Physics.