PSJC #113 March 27, 2012

Adrienne Dove (CU)

Experimental investigations of lunar plasma and dust dynamics

Surfaces of airless bodies and spacecraft in space are exposed to a variety of charging environments such that a balance of plasma determines the surface's charge. Photoelectron emission due to intense solar UV radiation is the dominant charging process on the sunlit lunar surface. To first order, this results in a positive surface potential, with a cloud of photoelectrons immediately above the surface, called the photoelectron sheath. Conversely, the unlit side of the body will charge negatively due the collection of the fast-moving solar wind electrons. The interaction of charged dust grains with these positively and negatively charged surfaces, and within the photoelectron and plasma sheaths, may explain the occurrence of dust lofting, levitation and transport above the lunar surface. In order to better understand these surface processes, we have performed laboratory experiments to study the physics of photoelectron sheaths above Zr, glass, CeO2, and JSC-1 surfaces in vacuum. Experimental measurements are compared with the results from a 1D PIC-code simulation to gain a greater understanding of the sheath physics.