Influence of the Lunar Dielectric Permittivity on Charging by the Solar Wind Plasma of Dust Grains on the Surface of the Moon

Electric charging of dust grains lying on the surface of the Moon is caused by the action of the solar wind plasma and the solar UV radiation. Near the terminator and in the shadow the charges on dust grains are negative and not too high for electrostatic lofting of such grains. That is why very strong electric fields are required to explain dust motion above the surface. Due to this various factors are taken into account to obtain stronger electric forces acting on dust grains. In the present paper it is investigated how the dielectric permittivity of the regolith and subsurface layers influence charging of dust grains on the Moon. We show theoretically that the dielectric permittivity in some regions can provide stronger (one order of magnitude and even more) electric charges of dust grains on the surface than it was estimated before.