On Dust Fractions of Various Compositions under the Conditions of Formation of a Dusty Plasma System near the Nucleus of a Comet

In a situation where dusty plasma can form in the vicinity of a comet’s nucleus, the influence of the dust composition at the surface of the nucleus on the plasma parameters, as well as on the composition of dust in the coma and tail of the comet, is considered. The cases of silicate and ice dust particles are discussed. It is shown that the influence of electrostatic effects in relation to the effects caused by the force of entrainment of a dust particle by a gas flow is weaker for ice particles than for silicate particles. Accordingly, the importance of ice particles in dusty plasma in the vicinity of comets, compared to silicate particles, becomes apparent at greater distances from the Sun. Furthermore, ice particles rising to certain heights are larger than silicate particles rising to the same heights. Accordingly, ice particles accumulate greater charges than silicate particles. For a comet with parameters of the nucleus close to those of comet 67P/Churyumov–Gerasimenko, the proportion of dust particles carried away by the gas flow from the cometary nucleus relative to their number on the surface of the cometary nucleus does not exceed a value of about 10%. In this case, the proportion of carried away ice dust particles relative to the number of ice dust particles on the cometary nucleus, and, accordingly, included in the composition of the comet’s dust coma and cometary tail, turns out to be several times greater than the proportion of carried away silicate dust relative to the number of silicate dust particles on the cometary nucleus.