THE DEPENDENCE OF THE VISCOSITY IN ACCRETION DISCS ON THE SHEAR VORTICITY RATIO/

We estimate the Shakura-Sunyaev viscosity parameter alpha for differen t values of the shear/vorticity ratio, sigma/omega, using local simula tions of dynamo-generated turbulence. We find that the time average of alpha is approximately proportional to sigma/omega (at least for sigm a/omega < 10). We point out that this result may have important implic ations for the properties of thick accretion discs, because there omeg a is small and alpha would then tend to be large. Our result may also be important for accretion discs around black holes, because sigma/ome ga becomes large in the inner 10 Schwarzschild radii as a result of re lativistic effects.