  Stellar atmosphere models of ionized accretion disks have generally neglected
the contribution of magnetic fields to the vertical hydrostatic support,
although magnetic fields are widely believed to play a critical role in the
transport of angular momentum. Simulations of magnetorotational turbulence in a
vertically stratified shearing box geometry show that magnetic pressure support
can be dominant in the upper layers of the disk. We present calculations of
accretion disk spectra that include this magnetic pressure support, as well as
a vertical dissipation profile based on simulation. Magnetic pressure support
generically produces a more vertically extended disk atmosphere with a larger
density scale height. This acts to harden the spectrum compared to models that
neglect magnetic pressure support. We estimate the significance of this effect
on disk-integrated spectra by calculating an illustrative disk model for a
stellar mass black hole, assuming that similar magnetic pressure support exists
at all radii.
