  Standard accretion disk theory is formulated which is based on the local heat
balance. The energy produced by a turbulent viscous heating is supposed to be
emitted to the sides of the disc. Sources of turbulence in the accretion disc
are connected with nonlinear hydrodynamic instability, convection, and magnetic
field. In standard theory there are two branches of solution, optically thick,
and optically thin. Advection in accretion disks is described by the
differential equations what makes the theory nonlocal. Low-luminous optically
thin accretion disc model with advection at some suggestions may become
advectively dominated, carrying almost all the energy inside the black hole.
The proper account of magnetic filed in the process of accretion limits the
energy advected into a black hole, efficiency of accretion should exceed $\sim
1/4$ of the standard accretion disk model efficiency.

Astrophysics