EFFECTS OF COMPRESSIBILITY, DIAMAGNETIC DRIFT, AND THERMAL CONDUCTION ON RESISTIVE BALLOONING MODES IN THE 2ND STABILITY REGIME

The stabilizing effects of various terms such as compressibility, diamagnetic drift, and parallel thermal conduction are investigated on the type of resistive ballooning modes whose driving force comes from the resistive region, which are known to be unstable in the high-beta second stability regime when analysed in the incompressible limit. It is found that compressibility gives a significant stabilizing effect mainly through the perpendicular magnetic compression, which suggests the possibility of a second stable window for these resistive ballooning modes. The diamagnetic drift terms slightly reduce the growth rate in the incompressible limit, but, with finite compressibility, lead to fairly strong stabilization. The compression due to ion polarization, which becomes significant at large diamagnetic drift, contributes to this stabilization. On the other hand, parallel thermal conduction and perpendicular magnetic compression, which enter through the equation for temperature evolution, are shown to have a negligible effect on the stability of these modes.