Dust dynamics in the lunar dusty plasmas: Effects of magnetic fields and dust charge variations

Abstract

The influence of the magnetic field of the Earth's magnetotail on dusty plasmas above the sunlit surface of the Moon is studied. For this purpose, a physical-mathematical model for a self-consistent description of dust grains and photoelectrons in the presence of the magnetic field is developed. Trajectories of motion of dust grains above the lunar surface are considered. It is shown that a distinguishing feature of the trajectory of a dust grain motion is the presence of oscillations. The process of damping of these oscillations is demonstrated to be related to variations of dust grain charges that is consistent with the concept of anomalous dissipation in dusty plasmas. We clarify whether dust grains in dusty plasmas above the sunlit lunar surface are “levitated” or “lofted.” The processes of dust grain charge variations are too fast in comparison with the day duration of the Moon. In this connection, for the majority of dust grains above the sunlit lunar surface, the oscillations are damped, and these grains can be considered as levitated. Only very fine grains do not go into “levitating” grain mode during the entire day on the Moon and can be treated as lofted those. A theory of dusty plasmas above the sunlit surface of the Moon, which takes into account the lunar gravity and the electrostatic processes but does not take into account the magnetic fields, explains the existence of dusty plasmas only for rather high lunar latitudes. The magnetic fields of the Earth's magnetotail are shown to provide a possibility of dust transport above the lunar surface, which can result in the existence of positively charged dust and correspondingly dusty plasmas at the sunlit side of the Moon for the whole range of the lunar latitudes.