The effects of compressibility of the resistive ballooning mode

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Abstract
The linear stability of the resistive ballooning mode, as described by the resistive magnetohydrodynamic (MHD) model, is investigated both analytically and numerically. When the pressure evolution is approximated by fluid convection (reduced MHD model), an instability driven by geodesic curvature, with a growth rate γ∼η1/3 β2/3p, is found. For conditions relevant to the Impurity Study Experiment (ISX‐B), it is shown that for modest poloidal bets (βp≂1), high current, and relatively high temperatures, compressibility has a significant stabilizing influence, relative to the pressure convection model. However, at high βp (≳2), low current, and lower temperatures, compressibility has much less effect.