Inhomogeneous Electrostatic Potentials on the Dayside Lunar Surface in the Terrestrial Magnetotail Lobes: The Role of Lunar Crustal Magnetic Fields

Masahisa Kato; Yuki Harada; Yoshifumi Saito; Shoichiro Yokota; Masaki N. Nishino; Futoshi Takahashi; Hisayoshi Shimizu; Shaosui Xu; Andrew R. Poppe; Jasper S. Halekas

doi:10.1029/2024JA033545

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Inhomogeneous Electrostatic Potentials on the Dayside Lunar Surface in the Terrestrial Magnetotail Lobes: The Role of Lunar Crustal Magnetic Fields

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Inhomogeneous Electrostatic Potentials on the Dayside Lunar Surface in the Terrestrial Magnetotail Lobes: The Role of Lunar Crustal Magnetic Fields

Masahisa Kato, Yuki Harada, Yoshifumi Saito, Shoichiro Yokota, Masaki N. Nishino, Futoshi Takahashi, Hisayoshi Shimizu, Shaosui Xu, Andrew R. Poppe and Jasper S. Halekas

Journal of geophysical research. Space physics, Vol.130(2), e2024JA033545

02/2025

DOI: 10.1029/2024JA033545

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Abstract

Though the Moon does not possess a global magnetic field like the Earth, there are localized crustal magnetic fields on the lunar surface. Because of the plasma interaction with the crustal magnetic fields, electrostatic and electromagnetic environments near magnetized regions can differ from those near non‐magnetized regions on the Moon. Previous studies observationally revealed the difference in the electrostatic potential on the lunar surface between magnetized and non‐magnetized regions of the Moon in the solar wind, which was attributed to upward electric fields formed by electron‐ion decoupling above the magnetic anomaly regions. However, these inhomogeneous distributions of surface potentials associated with lunar crustal magnetic fields remain uncharacterized in plasma regimes different from the solar wind. In this study, we use a large number of observations by Kaguya and a numerical model of photoelectrons emitted from the sunlit lunar surface to investigate the horizontal distributions of the lunar surface potential in the terrestrial magnetotail lobes. We estimate the relative surface potential variations from the measured energy shift of lunar surface photoelectrons. The results indicate that photoelectrons emitted from relatively strong crustal magnetic field regions tend to be more decelerated, suggesting more positive potentials on the magnetized surface. This implies that upward electric fields are formed by the interaction of terrestrial magnetotail plasma with the lunar crustal magnetic fields in a similar manner to the solar wind interaction with lunar crustal magnetic fields. The magnetic field configuration on the Moon is very different from that of the Earth, which has a global magnetic field, and there are many localized strong magnetic fields of crustal origin, and they are called “magnetic anomalies.” Because electrically charged particles interact with magnetic fields, previous studies reported that configurations of electric fields above the crustal magnetic field regions are different from those above non‐magnetized regions. These differences can be caused by inhomogeneities of surface charging. Since surface charging alters environments of dust and electricity near the lunar surface, information on surface charging is very important for lunar surface exploration. In order to understand how the local surface charging is related to the crustal magnetic field regions and various environments of charged particles, we compared a large number of observations of electron energy spectra by spacecraft orbiting around the Moon and a numerical model that describes electron energy spectra. Our analysis suggests that the local surface charging and electric field configuration above the crustal magnetic field regions also exist when the charged particle environment is different from the previous studies. Our results also imply that the spatial distribution of magnetic anomaly can be important for lunar surface exploration. Comparison of Kaguya observations with a photoelectron energy spectral model provides horizontal variations of the lunar surface potential More positive potentials are identified in stronger crustal magnetic fields on the lunar dayside in the terrestrial magnetotail lobes The results imply the ubiquitous formation of upward electric fields above the crustal magnetic fields in various plasma regimes

surface potential

the Moon

magnetic anomalies

Details

Title: Subtitle: Inhomogeneous Electrostatic Potentials on the Dayside Lunar Surface in the Terrestrial Magnetotail Lobes: The Role of Lunar Crustal Magnetic Fields
Creators: Masahisa Kato - Kyoto University
Yuki Harada - Kyoto University
Yoshifumi Saito - Japan Aerospace Exploration Agency
Shoichiro Yokota - Osaka Health Science University
Masaki N. Nishino - Japan Aerospace Exploration Agency
Futoshi Takahashi - Kyushu University
Hisayoshi Shimizu - Association for the Development of Earthquake Prediction
Shaosui Xu - University of California, Berkeley
Andrew R. Poppe - University of California, Berkeley
Jasper S. Halekas - University of Iowa
Resource Type: Journal article
Publication Details: Journal of geophysical research. Space physics, Vol.130(2), e2024JA033545
Publisher: AMER GEOPHYSICAL UNION
DOI: 10.1029/2024JA033545
ISSN: 2169-9380
eISSN: 2169-9402
Grant note: JST SPRINGJSPS KAKENHI Grant: JP22K14085, JP22H01285, JP22KK0045 Takenaka Scholarship Foundation
MK was supported by JST SPRING, Grant JPMJSP2110. YH acknowledges support through JSPS KAKENHI Grant (JP22K14085, JP22H01285, JP22KK0045). MK is supported by Takenaka Scholarship Foundation. MK wishes to thank Kumano dormitory community at Kyoto University for their generous financial and living assistance.
Language: English
Date published: 02/2025
Academic Unit: Physics and Astronomy
Record Identifier: 9984786445802771

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