Evaluation of cometary dust parameters from numerical simulations: comparison with an analytical approach and the role of anisotropic emissions.

Abstract

A numerical method is developed which models cometary dust tails by means of sample grains. The orbital motion of the grains is rigorously computed, avoiding any Finson-Probstein hypersonic condition and dust shell geometry approximation. The model is applied to the dust tails of Comet Seki-Lines 1962III and Comet Kohoutek 1973XII. The results show no significant differences from those obtained for these comets by Fulle (1988) using an inverse approach to the Finson-Probstein method. It is found that the dust velocities related to anisotropic dust ejections can be significantly higher than the velocities of dust ejected in isotropic shells. However, there is no direct relation between ejection anisotropy and the dust ejection velocity. It is shown that the dust tail analysis is quite insensitive to assumptions about the size dependence of the dust velocity.