Simulation study of the energetic neutral atom (ENA) imaging monitoring of the geomagnetosphere on a lunar base

Abstract

Since the moon’s revolution cycle is exactly the same as its rotation cycle, we can only see the moon always facing Earth in the same direction. Based on the clean particle radiation environment of the moon, a neutral atomic telemetry base station could be established on the lunar surface facing Earth to realize long-term continuous geomagnetic activity monitoring. Using the 20°×20° field of view, the 0.5°×0.5° angle resolution, and the ~0.17 cm²sr geometric factor, a two-dimensional ENA imager is being designed. The magnetospheric ring current simulation at a 4–20 keV energy channel for a medium geomagnetic storm (Kp=5) shows the following: 1) at ~60 Rᴇ (Rᴇ is the Earth radius), the imager can collect 10⁴ ENA events for 3 min to meet the statistical requirements for 2D coded imaging data inversion, so as to meet requirements for the analysis of the substorm ring current evolution process of magnetic storms above medium; 2) the ENA radiation loss puzzles in the magnetopause and magnetotail plasma sheet regions have been deduced and revealed using the 2-D ENA emission model. High spatial-temporal resolution ENA imaging monitoring of these two important regions will provide the measurement basis for the solar wind energy input process and generation mechanism; 3) the average sampling interval of ENA particle events is about 16 ms at the moon’s orbit; the spectral time difference for the set energy range is on the order of minutes, which can provide location information to track the trigger of geomagnetic storm particle events.