Viscous Diffusion Stage Of Evolution Of Protoplanetary Disks

The origin of the solar system is one of the most important questions in science. The standard theory of the origin of the solar system in the solar era is the nebular hypothesis.The current knowledge suggests that the viscosity in the solar nebular is not uniform and calculations of the nebular evolution with constantαmay miss usefull information about the history of solar system. It is pointed out that the angular momentum transport mechanism can be the magnetohydrodynamic turbulence driven by the magnetorotational instability. Considering the effect of ohmic diffusion on the magnetorotational instability in the solar nebular, it is pointed out that in the outer region of the nebular, the suface density is low enough for cosmic rays to penetrate and the ionization is high enough that the magnetorotational instability can survive. The magnetorotational instability can survive in the inner region due to thermal ionization. But the magnetorotational instability can not survive in the intermediate region between the inner region and the outer region, and the viscosity drops significantly. The angular momentum transport is not nonuniform and can not be described with a uniformα.In this paper, we present complete radial, time-dependent calculations of the structure and evolution of the protoplanetary disks during the viscous diffusion stage. The viscous stress is derived from the model of the vertical nebular structure based on detailed grain opacities. we investigate the viscous diffusion stage of evolution of protoplanetary disks by including nonuniform viscosity. The calculations are done by using currently accepted viscosity, which is nonuniform. In the calculation of viscosity, we include the effect of magnetorotational instability. The radial distributions of the suface density and other physical quantities of the nebular are significantly different from nebular models with constantαviscosity.We present complete radial, time-dependent calculations of the structure and evolution of the protoplanetary disks during the viscous diffusion stage. The viscous stress is derived from the model of the vertical nebular structure based on detailed grain opacities.