EFFECTS OF DIAMAGNETIC DRIFT AND COMPRESSIBILITY ON LINEAR RESISTIVE MAGNETOHYDRODYNAMIC STABILITY OF STELLARATORS

To study diamagnetic and compressibility effects for stellarators, tor oidally averaged equations describing resistive pressure-driven modes are developed. Linear stability results are given for cylindrical geom etry and toroidal geometry. When toroidal coupling is included, both t he analytical theory and numerical calculations show that diamagnetic effects can be destabilizing when they are small. However, for paramet ers appropriate to the Advanced Toroidal Facility (ATF) experimental d evice [J. F. Lyon et al., Fusion Technol. 10, 179 (1986)] the diamagne tic effects are large and stabilizing. The linear results also show th at for the specific cases reported here compressibility effects tend t o cancel toroidal effects. Cylindrical calculations which include diam agnetic effects may then be adequate for the study of the experimental data.