GLOBAL EVOLUTION OF SOLID MATTER IN TURBULENT PROTOPLANETARY DISKS .1. AERODYNAMICS OF SOLID PARTICLES

The problem of planetary system formation and its subsequent character can only be addressed by studying the global evolution of solid mater ial entrained in gaseous protoplanetary disks. We start to investigate this problem by considering the space-time development of aerodynamic forces that cause solid particles to decouple from the gas. The aim o f this work is to demonstrate that only the smallest particles are att ached to the gas, or that the radial distribution of the solid matter has no momentary relation to the radial distribution of the gas. We pr esent the illustrative example wherein a gaseous disk of 0.245 M. and angular momentum of 5.6 x 10(52) g cm(2) s(-1) is allowed to evolve du e to turbulent viscosity characterized by either alpha = 10(-2) or alp ha = 10(-3). The motion of solid particles suspended in a viscously ev olving gaseous disk is calculated numerically for particles of differe nt sizes. In addition we calculate the global evolution of single-size d, noncoagulating particles. We find that particles smaller than 0.1 c m move with the gas; larger particles have significant radial velociti es relative to the gas. Particles larger then 0.1 cm but smaller than 10(3) cm have inward radial velocities much larger than the gas, where as particles larger than 10(4) cm have inward velocities much smaller than the gas. A significant difference in the form of the radial distr ibution of solids and the gas develops with time. It is the radial dis tribution of solids, rather than the gas, that determines the characte r of an emerging planetary system.