Effects of ion diamagnetic drift on the m⁄n = 1 high-order harmonic modes in rotating tokamak plasmas

Abstract

The effects of ion diamagnetic drift on the high-order harmonic modes in rotating tokamak plasmas are numerically investigated by using a cylindrical reduced magnetohydrodynamic model. It is found that the ion diamagnetic drift has a stabilizing effect on the high-order tearing modes in the small ion diamagnetic drift regime and can excite the high-order Kelvin–Helmholtz (KH) instability in the large ion diamagnetic drift regime. The effects of ion diamagnetic drift flow on the tearing modes are different from those of the poloidal shear flow. Moreover, the combined effect of the two flows on tearing modes and KH modes depends on their relative direction. The eigenmode structures of the tearing modes and KH modes under the influence of ion diamagnetic drift flow are also presented. Finally, the numerical results are verified reasonably by the scalings on resistivity.