Evolution of Protoplanetary Disks with Condensation and Coagulation

Abstract

We investigate the global evolution of the viscous stage of a turbulent protoplanetary disk. The time-dependent radial development of the nebula is calculated with the help of analytical one-zone models of the vertical structure that relate optical properties of grains to turbulent viscosity. Special attention is given to possible growth of dust particles that cause significant opacity and hence viscosity changes. In the framework of a simple two-component model for the dust size population we follow the evolution of the total surface density of the disk. Assuming that grain growth is especially rapid in the main condensation regions (e.g., due to the enhanced sticking probabilities) we find significant surface density enhancements in these radially confined regions. Moreover, a lower turbulence strength in these regions (e.g., caused by the suppression of thermal convection) leads to a further increase in the density. Possible consequences for planet formation are briefly outlined.