Formation and Early Evolution of Protoplanetary Disks under Nonuniform Cosmic-Ray Ionization
Abstract: Angular momentum transport is one of the key processes controlling the evolution and structure of protoplanetary disks. Because protoplanetary disks are cold and dense, the gas is poorly ionizaed, and nonideal magnetohydrodynamic processes play a significant role in regulation of angular momentum transport.
In star and disk formation processes, the gas is mainly ionized by cosmic rays with relatively low energies. Since such cosmic rays are considerably attenuated by the gas, the cosmic-ray ionization is highly non-uniform and time dependent. Furthermore, recent observations suggest that forming protostars may be producing cosmic rays by themselves. In order to model such complicated interaction between the cosmic rays and dynamics in star and disk formation processes, we have been developing a new simulation code. In this talk, I will review recent observations of protoplanetary disks and their ionization states, and present our recent works on modeling star formation processes including the effects of cosmic rays.