Modeling dust coagulation and chondrule dust rim growth in a protoplanetary disk.

Coagulation of dust particles plays an important role in the formation of planets and is of key importance to the evolution of protoplanetary disks (PPD). Characteristics of dust, such as the diversity of particle size, porosity, charge, and the manner in which dust couples to turbulent gas, affect the collision process. In this work, a numerical model incorporating all of these effects is developed to simulate collisions between dust particles, which leads to dust growth, and between dust and chondrules, which results in fine-grained dust rims (FGRs) on chondrule surfaces. A Monte Carlo algorithm is used to randomly select colliding particles as well as determine the elapsed time interval between collisions. The actual collision outcome is determined by a detailed collision model which takes into account the morphology of the aggregates/FGRs,the trajectory/orientation of the colliding particles, and the electrostatic forces acting between charged grains by calculating the charge distribution on grain surface, etc. Dust growth and FGR formation are compared in environments with different turbulence strengths and different plasma conditions. The physical characteristics and timescales for growth of dust aggregates/FGRs over a range of nebular conditions are quantified, and the interplay between the effects of charge and turbulence on their evolution is investigated.