Enhanced Charging and Mobilization of Photoemitting Dust Particles in a Low‐Density Plasma

We present the first observations of dust charging and mobilization in a combined vacuum ultraviolet (VUV) and plasma environment. It is experimentally demonstrated that exposing photoemitting dust particles to a low‐density plasma enhanced the charge on the particles, accompanied by a significant increase in dust mobilization compared to VUV or plasma exposure alone. Measurements of the dust charge support a proposed ‘charge pumping’ mechanism, in which ambient electrons are collected by photoemitting dust surfaces, causing more photoelectrons to be pumped onto surrounding dust particles, increasing repulsive forces and leading to enhanced mobilization. Plain Language Summary On the surfaces of airless planetary bodies, phenomena such as the Lunar horizon glow, or the formation of dust ponds on the asteroid Eros are proposed to be the result of dust charging and mobilization by the solar wind plasma and vacuum ultraviolet (VUV) radiation. Laboratory experiments have demonstrated these charging and transport phenomena during dust exposure to VUV or plasma separately. Here we present the results of laboratory experiments on dust charging and transport during combined VUV and plasma. The mobilization of the dust particles was found to increase significantly in the combined case, compared to VUV or plasma alone. We propose a new mechanism, plasma charge pumping, in which the presence of ambient plasma electrons leads to larger charges developed on dust particles, resulting in increased electrostatic forces and therefore mobilization. These results provide strong evidence for the contribution of the solar wind to enhance dust charging phenomena on the illuminated areas on the Lunar surface. Key Points Dust piles exposed to both VUV and plasma are significantly more mobile than piles exposed to VUV or falone The charge on dust particles is enhanced in the combined case of VUV and plasma These observations show that the solar wind plasma may increase dust charging and mobilization on the illuminated surface of the moon