SPRG Seminars
March 16, 2010:
" Simulations of the Near-Surface Lunar Dusty Plasma Environment "
Andrew Poppe - LASP/CU Boulder
Previous observations have suggested a number of dusty plasma phenomena on the lunar surface, including dust charging, levitation and horizontal transport. These observations include Surveyor images of Horizon Glow (HG), astronaut sketches of dust “streamers” and in-situ measurements made by the Lunar Ejecta and Meteorite (LEAM) experiment. Recent laboratory experiments have approximately reproduced the near surface lunar plasma environment and shown that charging can lead to the levitation and transport of dust grains in a tenuous electron sheath. A critical ingredient to the observed phenomena is the presence of a photoelectron sheath, formed when solar ultraviolet radiation causes the lunar regolith to emit electrons. In order to understand the dynamics of dust particles on the surface of the Moon, the lunar photoelectron sheath has been modeled via a 1-dimensional particle-in-cell (PIC) code. Simulations have focused on the effects of a non-Maxwellian photoelectron velocity distribution and the presence of an incoming solar wind flux. Using the sheath profiles obtained by the PIC code, the charging and dynamics of micron-sized dust grains in the lunar photoelectron sheath are investigated. The presence of non-monotonic sheath potential profiles and their possible impact on the analysis of Lunar Prospector data will also be discussed