HR: 1400h
AN: SM23B-03    [Abstracts]
TI: Dependence of Lunar Surface Charging on Ambient Plasma Conditions and Solar Irradiation
AU: Stubbs, T J
EM: Timothy.J.Stubbs.1@gsfc.nasa.gov
AF: University of Maryland, Baltimore County, NASA Goddard Space Flight Center Mail Code 674, Greenbelt, MD 20771, United States
AU: * Halekas, J S
EM: jazzman@ssl.berkeley.edu
AF: U.C. Berkeley, Space Sciences Laboratory, 7 Gauss Way, University of California, Berkeley, CA 94720, United States
AU: Farrell, W M
EM: William.M.Farrell@nasa.gov
AF: NASA Goddard Space Flight Center, Science and Exploration Directorate, Greenbelt, MD 20771, United States
AU: Vondrak, R R
EM: Richard.R.Vondrak@nasa.gov
AF: NASA Goddard Space Flight Center, Science and Exploration Directorate, Greenbelt, MD 20771, United States
AU: Burchill, J K
EM: Johnathan.K.Burchill.1@gsfc.nasa.gov
AF: Natural Resources Canada, Geomagnetic Laboratory, Ottawa, ON K1A 0Y3, Canada
AU: Delory, G T
EM: gdelory@ssl.berkeley.edu
AF: U.C. Berkeley, Space Sciences Laboratory, 7 Gauss Way, University of California, Berkeley, CA 94720, United States
AU: Pfaff, R F
EM: Robert.F.Pfaff@nasa.gov
AF: NASA Goddard Space Flight Center, Science and Exploration Directorate, Greenbelt, MD 20771, United States
AB: The surface of the Moon is electrically charged by solar ultraviolet radiation incident on its dayside and the highly variable plasma environment that surrounds it. Lunar surface charging and the associated transport of charged dust could present hazards to future explorers, so developing a predictive capability for this environment will be a high priority. The main electric current sources come from the photoemission of electrons, plasma electrons, plasma ions, and the secondary emission of electrons. All four current sources can be very dynamic, which in turn results in a highly variable electrostatic potential and electric field at the lunar surface, both temporally and spatially. We present predictions for lunar surface potentials and electric fields for a variety of steady-state solar wind conditions. In addition, we also consider what happens when the Moon enters the hotter and more tenuous lobe and plasma sheet regions in the Earth's magnetotail. The main assumptions in deriving these predictions are that all the charged particle populations have a Maxwellian velocity distribution, and that as far as these populations are concerned the Moon's surface is an infinite plane. Since we focus mainly on the solar wind-lunar interaction, we initially neglect the effects of secondary electron emission, since this is often not a significant current source. The intention of this work is to develop a basic theoretical approach to making lunar surface charging predictions, which can be augmented by improvements in (1) our understanding of the current sources, (2) observational constraints, and (3) laboratory measurements. These initial predictions establish a "baseline" against which future theoretical and observational results may be compared, not just for the lunar case, but for all airless bodies such as Mercury and asteroids.
DE: 5421 Interactions with particles and fields
DE: 6025 Interactions with solar wind plasma and fields
DE: 6250 Moon (1221)
DE: 7855 Spacecraft sheaths, wakes, charging
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Joint Assembly