Abstract Details
| Name: Trinesh Sana Affiliation: Physical Research Laboratory Conference ID: ASI2025_278 Title : Effect of Solar Activity on The Lunar Plasma Environment Authors and Co-Authors : Trinesh Sana (1,2), S. K. Mishra (1) Abstract Type : Poster Abstract Category : Sun, Solar System, Exoplanets, and Astrobiology Abstract : The Sun greatly influences the plasma environment around the Moon. Without any significant atmosphere and global magnetic field, the Moon's surface is directly exposed to the solar wind and/or magnetospheric plasma and solar photons. Under exposure to dominant solar radiation, the sunlit lunar surface (and floating dust) generally acquires a positive charge and generates photoelectrons. The emitted photoelectrons and floating charged dust form a dusty photoelectron sheath in the vicinity of the lunar surface, which is a major component of the lunar dusty plasma environment. In contrast, plasma electrons typically predominate on the night side, and the surface acquires a negative charge and forms a classical plasma sheath. The complex electric potential/ field structures and dust dynamics within the lunar photoelectron sheath significantly depend on the solar vacuum ultraviolet (VUV; < 200 nm) radiation. The solar activity is highly variable in the range of 70–100 nm. Since the photoemission efficiency (quantum yield) of the lunar surface peaks in this range, the photoemission current and subsequent sheath characteristics significantly vary with solar activity. Here, we present a quantitative estimate of lunar photoelectron sheath characteristics using the high-resolution solar UV spectrum for different solar activity measured at 1 AU from the Flare Irradiance Spectral Model 2 (FISM2) and lunar photoelectron yield measured from sample return by the Apollo missions. This data will be used as the input parameters for a comprehensive photoelectron sheath model to derive the electric potential/field and population density profiles of the sheath constituents. The results demonstrate that under extreme solar flare conditions, the photoemission current increases significantly, which results in stronger potential and electric fields in the vicinity of the lunar surface. As a result, in extreme solar flare conditions, the electrostatic mobilization of lunar dust is anticipated to increase significantly. |