1. M3D to study the effect of isotropic viscosity and
thermal conductivity on results of CDX-U nonlinear simulation. (J. Breslau, C.
Isotropic viscosity and thermal conductivity terms have been implemented in M3D. Convergence studies were performed to determine the effects of these terms on linear growth rates of the n=1 mode for the CDX equilibrium with q(0)=0.82. For cases using the artificial sound term for parallel heat conduction, switching to isotropic viscosity was found to increase the growth rate by only about 6%, while switching to isotropic heat conduction did not result in a significant change in the growth rate. For cases without parallel heat conduction, switching to isotropic viscosity nearly doubled the n=1 growth rate, while switching to isotropic heat conduction as well in these cases reduced it by about 13%.
The nonlinear sawtooth run for the q(0)=0.92 equilibrium was repeated with isotropic viscosity switched on and 10 toroidal modes retained. The initial linear growth rate was found to be 20% higher than with the original perpendicular viscosity. The sawtooth period was reduced by 20% relative to the original case. Separation between kinetic energies in successive toroidal modes was less than before during termination of the crashes, but greater than before during the recovery periods in between. Stochasticity of the magnetic field following the crash was somewhat reduced. A numerical instability occurred in the n=10 mode as its energy dropped to near the background noise level, but this is not believed to have affected these results. A more implicit treatment of the leading-order part of the phi-derivative term in the isotropic operators is being considered to try to alleviate the instability.
2. Decide upon appropriate equilibrium for the ELM test cases. (S. Kruger, P. Snyder)