[P-PS06] Lunar Science and Exploration

[PPS06-P08] Characteristics of Auger electrons and photoelectron beams emitted from the dayside lunar surface in the terrestrial magnetotail

*Masahisa Kato¹, Yuki Harada¹, Shaosui Xu², Andrew R Poppe², Jasper S Halekas³, Yohei Miyake⁴, Hideyuki Usui⁴, Masaki N Nishino⁵ (1.Department of Geophysics, Graduate School of Science, Kyoto University, 2.Space Sciences Laboratory, University of California, Berkeley, 3.Department of Physics and Astronomy, University of Iowa, 4.Education Center on Computational Science and Engineering, Kobe University, 5.Japan Aerospace Exploration Agency, Institute of Space and Astronautical Science)

Since the Moon does not have an intrinsic dense atmosphere and strong magnetic field, the lunar surface is exposed to its ambient plasma environment. Surface charging is one of the phenomena resulting from interactions of the lunar surface with ambient charged particles and solar radiation. On the dayside of the moon, photoelectrons and Auger electrons are emitted from lunar surface and move along magnetic field lines and the electrons can be accelerated or decelerated by the electric field determined by the potential distribution above the surface.
Since Auger electrons have intrinsic energies characteristic of the emitting element, we can expect that observations of an energy shift of the Auger electron line enable us to infer the electrostatic potential at the surface level. In this study, we analyzed electron data from ARTEMIS, and have found a number of Auger electron events observed in the terrestrial magnetotail. A particular challenge we identified is that the energy resolutions of Electrostatic Analyzer (ESA) onboard ARTEMIS is not sufficiently high to fully resolve Auger electron’s energy shift in many cases. To overcome this difficulty and aid the interpretation of the observations, we develop a simple model of lunar photoelectron and Auger electron spectra. We report the status of the model development and data-model comparison.