The geomagnetic field on the thermosphere contains abundant information about solar activity, ion dynamics, global climate change, and Earth's interior. By now, most geomagnetic data is from satellite-born in-situ magnetic sensors. However, satellite-born in-situ schemes have some drawbacks, such as high expenses, measurement areas, etc. To address these drawbacks of satellite-born in-situ schemes, we put forward a remote sensing scheme based on Helium Lidar. Our scheme uses the metastable helium as tracing atoms, which is the dominant species of the thermosphere. In our scheme, we use a synchronous optical pumping method to detect the Larmor precession frequency of metastable helium in the thermosphere. The Larmor precession frequency is proportional to the strength of the geomagnetic field. We have simulated the signal with parameters from our current helium lidar in Hainan. Our simulation results show sensitivities of 5.15 nT/Hz1/2, 7.14 nT/Hz1/2, and 71.33 nT/Hz1/2 for D0, D1, and D2 lines of metastable helium with laser intensity of 10 W/m2. Sensitivity can further pe optimized by optimizing our lidar parameters.
Yin et al. (Thu,) studied this question.