Characteristics of Lunar Surface Electrons Inferred From THEMIS‐ARTEMIS Observations: 2. Photoelectrons

Abstract

The lunar surface charging is controlled mainly by the balance of electron currents near the surface. One of the main electron currents is the photocurrent on the dayside, comprised of photoelectrons produced by solar photons ionizing the lunar surface. Yet, there lacks a systematic characterization of the statistical properties of lunar photoelectrons. Photoelectrons can be uniquely identified by the oxygen Auger electron flux peak in the photoelectron energy spectrum. In this study, we develop a methodology to select lunar photoelectron measurements from the Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon's Interaction with the Sun (ARTEMIS) mission. With such a photoelectron database, we statistically analyze several properties of the lunar photoelectrons when the Moon is in the magnetotail lobe environment and in the solar wind environment, including how the photoelectron fluxes and the photoelectron detection probability vary and depend on driving parameters.