SPRG Seminars
March 11, 2014:
"Plasma-Neutral Interactions in the Lunar Exosphere"
Andrew Poppe, Space Sciences Laboratory, University of California, Berkeley
The moon is surrounded by a thin, collisionless collection of neutral particles collectively referred to as the lunar exosphere. Several processes are responsible for the generation of the lunar exosphere including internal gas release, thermal-, electron-, and photon-stimulated desorption, micrometeoroid bombardment, and sputtering by charged particles. Despite the overall weak nature of plasma-neutral coupling in the lunar exosphere, there nonetheless exist several examples of feedback and/or interaction between the neutral exosphere and the ambient plasma. We will present and discuss several findings regarding plasma-neutral interactions at the moon from both ARTEMIS in-situ spacecraft observations and accompanying modeling. These findings include the interaction of freshly born lunar pick-up ions with ambient lunar electrostatic fields, the process of self-sputtering, where pick-up ions re-impact the lunar surface to generate additional neutrals, and the role that lunar crustal magnetic anomalies play in modulating charged-particle sputtering production of the lunar exosphere. Such results are timely given the on-going Lunar Atmosphere and Dust Environment Explorer (LADEE) mission, currently in orbit around the moon measuring the lunar neutral and dust environment.