Abstract:

Starting from the equations of magnetohydrodynamics, the dispersion equation of accretion disks including anomalous viscosity,anomalous resistivity,azimuthal magnetic field and vertical magnetic field is derived from the perturbation method. It is numerically shown that there exist one monotonous mode of instability and three monotonous modes of stability in the inner disk region if  the magnetic field is weak, and the magnetic field acts as a factors of instability for the monotonous mode of instability. The monotonous modes diminish and there are four modes of oscillations in the disks when the magnetic fields strengthen. Two of them are always pulsationally stable, and the azimuthal magnetic field acts as a factor of instability, while the vertical magnetic field is the  stabilizing factor. The other two modes are instable if  the wave number is small, and they become stable when the wave number increases. The azimuthal magnetic field and vertical magnetic field act as factors of stability and instability, respectively.

Key words: anomalous viscosity; anomalous resistivity; instability; accretion disks; vertical magnetic field; azimuthal magnetic field