Observational Study on the Near-Ground Fair Weather Electric Field and Its Variations at LHAASO

Based on the near-ground Fair Weather Electric Field data recorded by the High-Altitude Cosmic Ray Observatory in Daocheng, Sichuan, from January 2020 to December 2021, this study analyzes the long-term variations and diurnal characteristics of the near-ground Fair Weather Electric Field in the Daocheng region, as well as its correlation with meteorological factors. The analysis of meteorological effects reveals that the long-term trends of the near-ground Fair Weather Electric Field in this region are largely consistent with three meteorological parameters (atmospheric pressure, temperature, and absolute humidity). The relationships between wind speed, aerosols, and the Fair Weather Electric Field are also discussed. The overall level of the Fair Weather Electric Field varies across seasons: approximately 0.13 kV/m in spring, 0.17 kV/m in summer, 0.14 kV/m in autumn, and 0.11 kV/m in winter. The Fair Weather Electric Field intensity is relatively higher in summer and lower in winter. The diurnal variation of the Fair Weather Electric Field exhibits a single-peak and single-trough pattern, with the peak occurring at 18:00 Beijing time and the trough at 7:00. The timing of these peaks and troughs varies slightly depending on the month. Additionally, the distribution characteristics of the diurnal variations of the Fair Weather Electric Field differ across months. These variations are related to meteorological parameters. Specifically, from November to February, the Fair Weather Electric Field primarily varies with temperature and wind speed, while from March to October, its distribution characteristics become more complex, influenced by other meteorological factors such as humidity. This study provides a comprehensive understanding of the Fair Weather Electric Field in the Daocheng region, highlighting its seasonal and diurnal patterns as well as its dependence on meteorological conditions. These findings contribute to advancing knowledge of atmospheric electricity and its interactions with local environmental factors。