  We investigate the effects of a large-scale magnetic field with open field
lines on the steady-state structure of a radiation-dominated accretion disk,
using self-similarity technique. The disk is supposed to be turbulent and
possesses an effective viscosity and an effective magnetic diffusivity. We
consider the extreme case in which the generated energy due to viscous and
magnetic dissipation is balanced by the advection cooling. While the magnetic
field outside of the disk is treated in a phenomenological way, the internal
field is determined self-consistently. Magnetized and nonmagnetized solutions
have the same radial dependence, irrespective of the values of the input
parameters. Generally, our self-similar solutions are very sensitive to the
viscosity or diffusivity coefficients. For example, the density and the
rotation velocity increase when the viscosity coefficient decreases. The gas
rotates with sub-Keplerian angular velocity with a factor less than unity which
depends on the magnetic field configuration. Magnetic field significantly
reduce disk thickness, however, tends to increase the radial velocity comparing
to the nonmagnetic self-similar solutions.
