Dissipation and Vertical Energy Transport in Radiation-Dominated Accretion Disks

Understand

Standard models of radiation supported accretion disks generally assume that diffusive radiation flux is solely responsible for vertical heat transport.

• This requires that heat must be generated at a critical rate per unit volume if the disk is to be in hydrostatic and thermal equilibrium.
• This raises the question of how heat is generated and how energy is transported in MHD turbulence.
• By analysis of a number of radiation/MHD stratified shearing-box simulations, we show that the divergence of the diffusive radiation flux is indeed capped at the critical rate, but deep inside the disk, substantial vertical energy flux is also carried by advection of radiation.