CSES Satellite Observation of Nightside Bremsstrahlung X-Ray Distributions Induced by Energetic Electron Precipitation

High-energy electrons can penetrate deeply into the ionospheric D-region, ionizing neutral molecules and producing reactive odd nitrogen and odd hydrogen, which ultimately impact the surface climate and temperature regime of the atmosphere. Although several instruments have been developed to measure precipitating electrons, accurately measuring precipitating electrons remains a highly challenging task. It is well known that high-energy electrons entering the lower ionosphere release both electrons and X-rays through a process known as bremsstrahlung radiation. By measuring the X-rays produced through this process, the flux of the precipitating electrons can be derived. In recent years, there have been numerous observations of X-ray emissions recorded by balloons-based measurement, but relatively few have been recorded from satellites. We analyze the characteristics of X-rays distribution detected by the CSES satellite from 2019 to 2022. The results indicate that the distribution of X-ray rates on the nightside corresponds closely with precipitated energetic electrons, especially at energies below 800 keV. Bremsstrahlung X-ray rates significantly increase when the Kp index exceeds 2 in high-latitude regions. X-rays generated by lightning-induced electron precipitation are primarily found in the region where 2.5 < L < 3, spanning 150°E to 260°E in the northern hemisphere and 300°E to 360°E in the southern hemisphere.