Formation and Structure of Protostellar Accretion Disks

The physics of accretion disks revolves around the two issues of how disks form and how angular momentum is transported within them. In the case of cataclysmic variables, the formation mechanism is well understood to be a Roche lobe overflow in a low mass, binary stellar system. There is increasing evidence for the existence of accretion disks around young stellar objects. Both low and high mass star formation regions contain protostellar disks (eg.; S106 and HL Tau respectively) and these are at least a tenth the mass of the central star (and perhaps more). While the angular momentum transport mechanisms in all types of disks could be similar, their formation mechanisms are of course not. Disks in molecular clouds could be produced as a consequence of gravitational instability and collapse in strongly magnetized, dense, cold gas.