Mischishina I. The peculiarities of dynamics the coarse dust particles in comet atmosphere

Theoretical modeling of the thermal relaxation was preformed for grains sublimating under the solar radiation. The relaxation time of the grain temperature to the equilibrium state was calculated, one dependence on grain size drastically differs for ice grains polluted carbon and those polluted by silicate and can amount to several minutes at 1a.u. The nonequilibrium thermal radiation of the particles was studied. Using phase plane method the possibility of stable location of dust grains in the comet atmosphere with weak dust content was studied. The simulation was made using the hydro-dynamical symmetrically spherical gas flow and Knudsen boundary layer. It was shown that the dust particles could have two equilibrium points one of which is a point of stable equilibrium. For the nucleus of 2.5km at 2a.u. this point occurs at 10-1000km and corresponds to the grains of 4.5-0.5cm size and 1g/cm3 density. The simulation of trajektories of big dust grains was made. Terminal velocity versus dust size was calculated for their different initial velocities. Parameters of the grains that can be trapped into the stable equilibrium points were obtained. In the steady atmosphere the process of ballistics accumulation has low probability. Contrary in the dynamic atmosphere the probability of trapping of grains increases.