Research on Temporal and Spatial Characteristics of 50/60Hz Electromagnetic Background Based on CSES Satellite Observation

Power Line Emission (PLE) generated by ground power systems has been receiving close attention in recent years. To enhance the precision in identifying and researching the PLE phenomenon in the topside ionosphere, the investigation of the electromagnetic background without PLE is necessary. The Extremely Low Frequency (ELF) electric field data of the China Seismo-Electromagnetic Satellite (CSES) during the three years (2019–2021) have been used to study the background at 50/60Hz. A statistical study was conducted on the differences in the impact of geomagnetic activity and lightning on the background in different regions and at different times. By analyzing the temporal and spatial distribution characteristics of the background, it is found that the geomagnetic activity may not affect the 50/60Hz electromagnetic background in the top ionosphere. The seasonal changes in areas with high lightning occurrence are very obvious at night, while in areas with less lightning, there is almost no seasonal change. Therefore, it is believed that the 50/60Hz electromagnetic background at night may be mainly affected by the proton whistler waves from lightning activities.