Journal article
Lunar Photoemission Yields Inferred From ARTEMIS Measurements
Journal of geophysical research. Planets, Vol.126(6), e2020JE006790
06/2021
DOI: 10.1029/2020JE006790
Abstract
Photoemission yield (the number of emitted electrons per incoming photon) is one of the fundamental properties of solid materials but is not yet well constrained for the lunar surface for photon energies >∼20 eV. In this study, we constrain this yield for incident photons with energies of ∼10–500 eV with data from the Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon's Interaction with the Sun (ARTEMIS) mission along with solar irradiance spectra from Version 2 of the Flare Irradiance Spectral Model. We also report the first oxygen Auger electron observations at the Moon by the ARTEMIS spacecraft, which provides a unique feature to identify photoelectrons emitted from the lunar surface. With lunar photoelectron observations identified in both Earth's magnetotail lobes and the solar wind for four selected days, we infer a lower bound of 10−3 in yield for photon energies >∼20 eV. However, our investigation also reveals an uncertainty over ∼4 orders of magnitude in derived yields with a sensitivity study, owing to a poorly constrained photoelectron energy probability function. This uncertainty motivates future experiments on lunar samples to better characterize the lunar surface charging environment.
Plain Language Summary
The photoemission yield (the number of emitted electrons per incoming photon) is one of the fundamental properties of solid materials, but not yet well constrained for the lunar surface for photon energies >∼20 eV (electron volts). A better understanding of lunar surface photoemission yield is also important for characterizing the lunar electrostatic charging environment, as lunar photoelectrons contribute to one of the dominant currents at/near the lunar surface. This study utilizes measurements from the Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon's Interaction with the Sun mission and also full solar irradiance spectra from a model to determine this yield. While we can infer a lower bound in yield for photon energies >∼20 eV, we find an uncertainty over ∼4 orders of magnitude in derived yields, which motivates future experiments on lunar samples to better characterize the yield function.
Key Points
We make the first report of oxygen Auger electron observations at the Moon by the Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon's Interaction with the Sun spacecraft
We infer a lower bound of 10−3 in photoemission yield of the lunar surface for photon energies >∼20 eV
Uncertainties over four orders of magnitude in yields are found, motivating future experiments on lunar samples for a better understanding
Details
- Title: Subtitle
- Lunar Photoemission Yields Inferred From ARTEMIS Measurements
- Creators
- Shaosui Xu - University of California, BerkeleyAndrew R. Poppe - University of California, BerkeleyYuki Harada - Kyoto UniversityJasper S. Halekas - University of IowaPhillip C. Chamberlin - Laboratory for Atmospheric and Space Physics
- Resource Type
- Journal article
- Publication Details
- Journal of geophysical research. Planets, Vol.126(6), e2020JE006790
- DOI
- 10.1029/2020JE006790
- ISSN
- 2169-9097
- eISSN
- 2169-9100
- Number of pages
- 13
- Grant note
- German Ministry for Economy and Technology and the German Center for Aviation and Space (DLR) (50 OC 0302) National Aeronautics and Space Administration (NASA) (NNX14AG16A; NNX15AH15A; 80NSSC18K1565; NAS5‐02099)
- Language
- English
- Date published
- 06/2021
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984428766802771
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