MHD modes driven by anomalous electron viscosity and their role in fast sawtooth crashes

The dispersion relations are derived for both small and large delta' modes (m is greater than or = to 2, and m = 1 modes, respectively) driven by anomalous electron viscosity. Under the assumption that the anomalous kinematic electron viscosity is comparable to the anomalous electron thermal diffusivity, we find that the viscous mode typically has a higher growth rate than the corresponding resistive mode. Computational results in cylindrical and toroidal geometries are compared with theory and some nonlinear results are presented for viscous m = 1 modes in both circular and D-shaped boundaries and their possible rile in fast sawtooth crashes are discussed.