Stabilization of Short Wavelength Resistive Ballooning Modes by Ion-to-Electron Temperature and Gradient Ratios in Tokamak Edge Plasmas

We numerically investigate the effects of ion-to-electron temperature ratio T_\rm i/T_\rm e and temperature gradient ratio \eta_\rm i/\eta_\rm e on resistive ballooning modes (RBMs) under tokamak edge plasma conditions. The results show that the growth rates of the RBMs exhibit the characteristic of a quite broad poloidal wavenumber spectrum in the cold ion limit. The growth rate spectrum becomes narrower and the peak of the spectrum shifts from the short to long wavelength side with increasing T_\rm i/T_\rm e and \eta_\rm i/\eta_\rm e. The electron temperature gradient has a very weak effect on the stability of RBMs. However, the ion-to-electron temperature ratio and the temperature gradient ratio have strong stabilizing effects on short-wavelength RBMs, while they have relatively weak effects on long-wavelength RBMs.