Numerical study of drift-resistive modes in general toroidal geometry

Abstract

The linearized resistive boundary layer equations, including electron diamagnetic drift terms in general toroidal geometry, are solved numerically to obtain the dispersion relations of the resistive ballooning modes as well as the resistive interchange and tearing modes in both highly collisional and semicollisional regimes. Numerical solutions with high accuracy are obtained using two different numerical methods. Various physical effects, such as electron diamagnetic drift, parallel and perpendicular compression, and average curvature, are investigated in a wide range of equilibrium parameters. The present work is believed to be the first numerical study of the resistive ballooning modes with finite electron diamagnetic drift effects. These numerical solutions cover a wider range of parameter spaces than thus far available from analytical and other numerical methods. The new solutions contain previously known results as special cases. 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 modes, these numerical results are shown to be in good agreement with previous results.