  In this letter, we present numerical calculations made to investigate the
possible resolution dependence of the Shakura & Sunyaev (1973) viscosity
parameter alpha from local magnetohydrodynamic simulations of the
magnetorotational instability (MRI). We find that the values of alpha do indeed
depend significantly on the numerical resolution but also that when the highest
resolutions attainable by the computational resources available are used, the
growth of the alpha-parameter seems to saturate. The values of alpha are at
most of the order of 10^(-3), which indicates that the sole presence of
turbulence due to dynamo generated magnetic field in the disk is not enough to
reproduce alphas of the order unity which could explain some observational
results (e.g. Cannizzo 1993).
