Averaged cold plasma equations for ion cyclotron waves in stellarators

Abstract

When the toroidally varying component of a stellarator equilibrium is much smaller (larger) than the helically varying component, the cold plasma equations can be averaged over the helical (toroidal) angle to yield a two-dimensional description of ion cyclotron wave propagation. Higher order corrections may be computed iteratively; at each step only a two-dimensional operator need be inverted. Since the cold plasma equations have a singularity at the cyclotron resonance, a special coordinate system is introduced that exactly represents the resonance surface.