Analytic Model for Advection-Dominated Accretion Flows in a Global Magnetic Field

A model for advection-dominated accretion flows (ADAFs) in a global magnetic field is proposed. In contrast to the well known ADAF models in which the viscosity of a fluid determines both angular momentum transfer and energy dissipation in the flow, the magnetic field and the electric resistivity, respectively, control them in this model. A manageable set of analytic solutions for the flow and the magnetic field is obtained to vertically non-integrated basic equations. This set describes mathematically a fully advective accretion flow and, in physically plausible situations for most AGNs, it is also confirmed that the radiation cooling estimated on this solution is really negligible compared with the internal energy of the flow.Comment: 27pages, 1 figure, to appear in ApJ vol 529, Feb.1, 200