Non-ideal MHD ballooning modes in three-dimensional configurations

A linear stability theory of non-ideal MHD ballooning modes is investigated using a two fluid model for arbitrary three-dimensional electron-ion plasmas. Resistive-inertia ballooning mode (RIBM) eigenvalues and eigenfunctions are calculated for a variety of equilibria including axisymmetric shifted circular geometry (s − α model) and configurations of interest to the Helically Symmetric Stellarator (HSX). For parameters of interest to HSX, characteristic growth rates exceed the electron collision frequency. In this regime, electron inertia effects dominate plasma resistivity and produce an instability whose growth rate scales with the electromagnetic skin depth. Attempts to generalize previous analytic calculations [1] of RBM stability using a two scale analysis on s − α equilibria to more general 3-D equilibria will be addressed.