Formation of Dusty Plasma in the Vicinity of Comet 67P/Churyumov–Gerasimenko

Plasma–dust processes for a comet with nucleus parameters close to those of the comet 67P/Churyumov–Gerasimenko nucleus are analyzed. The distribution functions of photoelectrons, altitude dependences of electric fields, as well as charges and sizes of dust particles, are determined using a physicomathematical model that allows for a consistent description of concentrations of photoelectrons and dust particles above the illuminated part of the comet nucleus. It is demonstrated that plasma–dust processes reveal themselves distinctly when the distance from the comet to the Sun is at least ~5 AU. In this case, dusty plasma in the vicinity of the nucleus of a comet with parameters close to those of the comet 67P/Churyumov–Gerasimenko nucleus is formed due to electrostatic interactions, i.e., similar to the formation of dusty plasma near atmosphereless celestial bodies, such as the Moon, Mercury, and asteroids. On the contrary, if a comet is closer to the Sun, the dust-particle dynamics is determined by the gas outflow from the comet nucleus. The albedo of the comet nucleus represents an important factor influencing the formation of dusty plasma in the vicinity of the nucleus. Comet 67P/Churyumov–Gerasimenko is characterized by a relatively low albedo. As a result, dusty plasma formed due to electrostatic interactions in the vicinity of its nucleus can be observed only in a short segment of its orbit close to aphelion. Had the albedo been an order of magnitude higher, the influence of the plasma-dust processes would have to be taken into consideration in a substantially wider range of comet distances from the Sun.