Linear stability of resistive magnetohydrodynamic(MHD) modes in general toroidal geometry

Abstract

The Linearized resistive MHD boundary layer equations, including the electron diamagnetic drift, compression, and electron temperature gradient terms in general toroidal geometry, are solved numerically to obtain the dispersion relations of the three resistive MHD modes of resistive interchange, tearing, and ballooning. Numerical solutions with very high accuracy are obtained using two different numerical methods. Various physically interesting problems, such as electron diamagnetic drift effects coupled with compression and average curvature, and ETG(effects of temperature gradient coupled with thermal conduction and transport) are investigated in a wide range of parameters. From the present study it is found that for the resistive ballooning and tearing modes, which have similar forms of dispersion relation, ion sound compression gives a substantial stabilizing effect, while ion polarization compression gives a destabilizing effect and the stabilizing effect of favorable average curvature is significantly reduced as the diamagnetic drift effect increases. For the resistive interchange mode, these numerical results are in good agreement with previous results. On the other hand, for the ETG, it is shown that it gives a substantial stabilization to the resistive ballooning and tearing modes, while the resistive interchange mode is destabilized by this effect. Though most of these findings are in good agreement in their essential points with existing work, the conclusion associated with the resistive ballooning mode appears to be in disagreement with some aspects of previous work. An analysis of the reasons for this discrepancy is presented.