Global evolution of solid matter in turbulent protoplanetary disks

Tile problem of planctary system formation and its subsequent character can only be addressed by studying the global evolution of solid material 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 dccouple from the gas. The aim of this work is to demonstrate that only the smallest particles are attached to the gas, or that the radial distribution of the solid matter has no momentary relation to the radial distribution of the gas. We present the illustrative example wherein a gaseous disk of 0.245 3.,fc_and angular momentum of 5.6 × 1052 gcm 2 s-1 is allowed to evoh'e due to turbulent viscosity characterized by either c_ = 10-2 or o, = 10-3. The motion of solid particles suspended in a viscously evolving gaseous disk is calculated numerically for particles of different sizes. In addition we calculate the global evolution of single-sized, noncoagulating particles. We find that particles smaller than 0.1 cm move with the gas; larger particles have significant radial velocities relative to the gas. Particles larger then 0.I cm but smaller than 10 3 cm have inward radial velocities much larger than the gas, whereas particles larger than 104 cm have inward velocities much smaller than the gas. A significant difference in the form of the radial distribution of solids and the gas develops with time. It is the radial distribution of solids, rather than the gas, that determines the character of an emerging planetary system.