A Monte Carlo model for the flow of dust in a porous comet nucleus

We describe a Monte Carlo model that simulates dust migration in a porous c ometary nucleus. We present computations for media in which the pore-size d istributions are either random or normal; additional computations indicate that media with power-law size distributions behave very similarly to rando m distributions. We show how the average time to cross the medium varies as a function of porosity and how the structure of the medium varies with tim e. Implications for the structure of the cometary nucleus are discussed. (C ) 1999 Academic Press.