Magnetically supported disks

Since the finding that the magneto-rotational instability can transport angular momentum outward, the role of magnetic fields has been confined to producing an effective viscosity in standard accretion disk models. However, in the past ten years simulations have shown that the properties of strongly magnetized disks largely deviate from standard models. The magnetic field can support the disk vertically, can produce accretion through vertically elevated layers or non-axisymmetric structures and remove angular momentum through strong laminar stresses. All of these effects dramatically affect the observational signature of accretion disks. In this talk, I will show a comprehensive analysis of a set of GRMHD simulations showing how the properties of strongly magnetized accretion disks vary when going from thick, hot disks to cold, thin disks. I will focus on how the magnetic field can affect the dynamical structure of accretion disks and in turn their radiative properties.