  We add the $\alpha-$ effect in the dynamo driven accretion disk model
proposed by Tout & Pringle (1992), i.e., a dynamo model depends on the physical
processes such as Parker instability, Balbus-Hawley instability, magnetic field
reconnection and $\alpha-\omega$ mean field dynamo as well. The $\alpha-$
effect in the dynamo mechanism is determined by the strength of turbulence of
the accretion flow. When the turbulent Mach number $M_t$ is less than 0.25, the
solutions of the magnetic fields oscillate around their equilibrium values. The
increase of the value of $M_t$ makes the amplitude of the oscillation smaller
and the period longer, but does not affect the equilibrium values. The
Shakura-Sunyaev viscosity parameter $\alpha_{SS}$ oscillates around the
equilibrium value of 0.33. When the turbulent Mach number $M_t$ is larger than
0.25, the magnetic field components reach a stable state. In the non-linear
dynamo region, the critical turbulent Mach number $M_t$ is 0.44 rather than
0.25. The oscillating magnetic fields and viscosity parameter can explain the
basic properties of the dwarf nova eruptions and some properties of quiescent
disks (Armitage et al. 1996).
