EFFECT OF VISCOUS DISSIPATION ON THE GENERATION OF SHEAR-FLOW AT A PLASMA EDGE IN THE FINITE GYRO-RADIUS GUIDING CENTER APPROXIMATION

A numerical simulation is performed to study the effect of a viscous d issipation term on the generation of shear how at a plasma edge in the guiding center approximation. The guiding center model includes the e ffects of finite Larmor radius corrections and polarization drift. The numerical code applies the method of fractional steps to the fluid gu iding center equations. We attempt to discriminate between the smoothi ng of the microstructure by a small viscous dissipation term to contro l numerical instabilities, and the modification of the macroscopic phy sical results introduced by this small viscous dissipation term. The f inite Larmor radius effect allows for a charge separation to exist, wh ich can be further accentuated by the polarization drift. A difference in the viscous term between electrons and ions can add to the charge separation effect at the plasma edge, which can modify the physical re sults. The numerical calculation is effected using a slab model, perio dic in one direction and finite in the other direction, with an inhomo geneous density of guiding centers to simulate a plasma edge. The evol ution of the system shows the potential evolving to a shape characteri zed by the longest wavelength associated with the transverse dimension of the system, an evolution characteristic of an inverse cascade. We present an analysis of the effect of different values of the viscous t erm on the time evolution of this guiding center system, and on the fo rmation and existence of a charge separation and an electric held at t he edge of a plasma and the associated shear in the E x B flow.