Charged dust dynamics above the surface of a comet far from the Sun

We investigate the dynamics of small dust particles ejected from the sunlit side of the nucleus of a comet far from the Sun. The motion of these particles is determined by gravity, electromagnetic forces, and solar radiation pressure. The nucleus is not shielded from either the solar wind or the solar UV radiation; therefore the surface of the nucleus absorbs electrons and protons and emits photoelectrons. As a result, the surface gets positively charged. Above the nuclear surface a photoelectron plasma sheath forms in which the ejected dust grains collect electrostatic charges and become responsive to the electric field in the sheath. We show that most of the dust cloud created by an impact (e.g., a lander) will settle after a few (similar to 4) hours elsewhere and not, in the close vicinity of the impact site (i.e., on the lander itself).