THE SOLAR NEBULA AS A PROCESS - AN ANALYTIC MODEL

We have constructed an analytic model of the solar nebula based on a t ime-dependent accretion disk theory. Until now, this problem has been solved only numerically. Our model offers explicit formulas for a spat ial structure and temporal evolution of the nebula. The model is chara cterized by only three major parameters: initial mass of the nebula, i nitial angular momentum of the nebula, and viscosity parameter alpha. The values of these parameters are relatively well constrained. Models of the solar nebula obtained using our formulas are in good agreement with previously published numerical results. An analytic model has th e advantage of embodying all the different scenarios, thus providing m uch deeper insights into the dynamical evolution of the nebula. We hav e found that the evolution of the nebula passes through different epoc hs, each characterized by a different rate of evolution. The number of different epochs, and thus the character of the evolutionary history of the nebula, depends on a particular set of parameters. We have show n that very different evolutionary scenarios arise from even modest ch anges in the values of the parameters. The analytic model can help to link disk theory to observations, as well as to provide a valuable too l for cosmogonic studies. (C) 1998 Academic Press.