Solar Activity Dependence of the Dayside Lunar Surface Potential in the Terrestrial Magnetotail

Masahisa Kato; Yuki Harada; Shaosui Xu; Andrew Poppe; Jasper S Halekas

doi:10.1029/2025GL120581

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Solar Activity Dependence of the Dayside Lunar Surface Potential in the Terrestrial Magnetotail

Journal article

Peer reviewed

Solar Activity Dependence of the Dayside Lunar Surface Potential in the Terrestrial Magnetotail

Masahisa Kato, Yuki Harada, Shaosui Xu, Andrew Poppe and Jasper S Halekas

Geophysical research letters, Vol.53(5), e2025GL120581

03/16/2026

DOI: 10.1029/2025GL120581

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Abstract

On the dayside of the Moon, the surface potential is primarily determined by (a) photoelectron emission by solar radiation and (b) the ambient plasma environment. Both of these drivers have large variability, but the resulting variability of the lunar surface potential has not been fully characterized yet. To investigate the solar activity dependence of the dayside lunar surface potential in the terrestrial magnetotail, we compared long‐term observations of lunar surface photoelectrons with numerical calculations of photo‐emitted electron energy spectra. The comparison demonstrates that the observed solar activity dependence of lunar photoelectrons is well reproduced by the model. The current balance surface potential based on this model predicts more positive potentials for higher solar activities, possibly exceeding +100V ${+}100\ \mathrm{V}$ in the magnetotail lobes during solar flares. These results highlight the importance of evaluating the lunar electrostatic environment under various conditions, including extreme solar events.

Charged particles

Electron energy

Energy

Energy spectra

Lunar surface

Magnetic fields

Magnetotails

Moon

Photoelectrons

Plasma

Solar activity

Solar cycle

Solar flares

Solar radiation

Spectral emittance

Surface potential

Variability

Details

Title: Subtitle: Solar Activity Dependence of the Dayside Lunar Surface Potential in the Terrestrial Magnetotail
Creators: Masahisa Kato
Yuki Harada
Shaosui Xu
Andrew Poppe
Jasper S Halekas
Resource Type: Journal article
Publication Details: Geophysical research letters, Vol.53(5), e2025GL120581
DOI: 10.1029/2025GL120581
ISSN: 0094-8276
eISSN: 1944-8007
Publisher: John Wiley & Sons, Inc
Grant note: JSPS KAKENHI: 25K00024, 25H00684, 25K01053 JST SPRING: JPMJSP2110 NASA's Lunar Data Analysis Program grant: 80NSSC25K7047
MK was supported by JST SPRING, Grant JPMJSP2110. YH acknowledges support through JSPS KAKENHI Grant (25K00024, 25H00684, 25K01053). SX and AP gratefully acknowledge support from NASA's Lunar Data Analysis Program Grant 80NSSC25K7047.
Language: English
Date published: 03/16/2026
Academic Unit: Physics and Astronomy
Record Identifier: 9985139298502771

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