Enhanced Current Penetration in Plasmas Due to Anomalous Viscosity

An investigation is made of the anomalous current penetration in a plasma in the presence of turbulence-induced viscosity. Exact similarity solutions are found for the characteristic nonlinear diffusion equation determining the, current penetration and approximate solutions are presented, which describe the evolution of smooth initial current profiles. Comparisons with previous numerical results show good agreement. The results indicate that the anomalous viscosity should be very efficient in smoothing out sharp current gradients, but should not be important on length scales comparable to the minor radii of modern tokamaks.