Lunar atmosphere plasma and fields

Abstract

The lunar atmosphere, ionosphere, plasma, and fields form a complex, interactive system with the surface and interior. The Moon is exposed to solar wind plasma and electric and magnetic fields, as well as the Earth's magnetotail where it may encounter rapidly moving plasmoids. The lunar atmosphere is intimately coupled to the lunar surface and interior. Sources of the lunar atmosphere include venting of the interior (e.g. Ar 40) as well as lunar surface elements released into the atmosphere by solar wind and magnetospheric sputtering and by micrometeorites. In addition to the solar wind electric fields exist at the lunar surface due to a balance between local charging mechanisms. For the Moon in the solar wind, resulting electric potentials are expected to range from +5 to +10 volts on the dayside to −10's to −100's of volts on the nightside. Ions formed in the atmosphere or at the surface are accelerated by the surface electric fields and solar wind electric and magnetic fields. We show that the result is a strong flux of atmospheric and sputtered ions that readily can be detected by an ion spectrometer in lunar orbit or on the surface, giving comprehensive information about the atmospheric and surface composition.