Editing Openai/67b71e2c-cc10-8008-9939-dfe494d1384d (section)

=== Assistant: During the lunar night, the surface voltage of the Moon is influenced primarily by the interaction of the surface with … ===
During the lunar night, the surface voltage of the Moon is influenced primarily by the interaction of the surface with the solar wind plasma and the ambient space environment, rather than direct photoelectric charging from sunlight.

===== - The minimum surface voltage of the lunar night side is estimated to be around -100 V to -200 V, but it can vary depending on location and plasma conditions. =====
* This negative charging occurs because: - The lunar surface is in shadow and does not experience photoelectron emission (which occurs on the sunlit side). - Electrons from the solar wind (or the plasma sheet when the Moon is in Earth's magnetotail) deposit a net negative charge on the surface. - The lack of photoemission means that there is no balancing positive charge, leading to an accumulation of negative charge.

===== 1. Solar Wind Plasma Density & Energy - In the normal solar wind (when the Moon is not inside Earth's magnetotail), the night-side voltage is estimated to be around -100 V to -200 V. - If solar wind density is higher, the negative charge accumulation could increase. =====
# Earth’s Magnetotail Influence - During part of its orbit, the Moon passes through Earth's magnetotail plasma sheet, which can cause the surface potential to vary. - Some measurements and models suggest that voltages could drop to -500 V or even lower in these conditions.
# Local Surface Composition & Topography - Rough terrain or crater edges may have locally stronger electric fields. - The presence of insulating dust (regolith) affects how charge distributes.

===== - Day Side: Lunar surface voltage can be +5V to +10V, and in extreme cases, up to +100V, due to UV-driven photoemission. =====
* Night Side: There is no UV, so charging is controlled by the balance of electrons and ions in the plasma environment, leading to a negative surface potential.

===== - Minimum surface voltage during lunar night: Typically -100V to -200V, but can drop to -500V or lower in Earth’s magnetotail. =====
* Why? Lack of photoemission, electron accumulation from the solar wind or magnetotail plasma.
* Implications: Strong negative charging could influence dust movement and spacecraft charging when landed on the Moon’s dark side.

Would you like more details on how these values were measured or modeled?