Ionosphere D-Layer Observation At Low-Latitude In East Asia Using Lightning Radiation Signals

The D-layer of the ionosphere refers to the atmospheric plasma layer located 5090 km above the ground,which is directly coupled to the lower atmosphere.The structural changes of the D-layer are mainly modulated by solar activity and are also affected by space weather activities such as cosmic rays and lower atmospheric activities.These changes can have important impacts on radio communication and navigation.However,traditional detection methods such as rockets and radar have certain temporal and spatial limitations and are expensive.Currently,using lightning as a signal source to detect the D-layer has become a hot research topic for scholars at home and abroad.By inverting the lightning waveform containing D-layer reflection information,high spatiotemporal resolution observations of the D-layer can be achieved.Previous research has made significant progress in detecting the D-layer in mid to high latitudes,but research on low-latitude regions of East Asia is still insufficient,especially regarding the impact of space weather activities on the D-layer.This study used continuous four-year summer thunderstorm data recorded by the Jianghuai Area Sferic Array to invert the D-layer virtual height for four consecutive Junes in low-latitude regions of China.The temporal and spatial characteristics of Dlayer virtual height during daytime,sunrise and sunset,and nighttime were statistically analyzed.The study also explored the effects of solar activity and geomagnetic disturbances on the D-layer,combined with space weather data.The main results are summarized as follows:(1)During the daytime,the D-layer height is mainly dominated by the solar zenith angle,while on a longer monthly time scale,the behavior of the D-layer height shows a significant negative correlation with solar shortwave radiation.(2)During the sunrise and sunset stages,the average formation speed of D-layer sunrise is 5 km/h,and the average dissipation speed of D-layer sunset is 7.3 km/h.It is particularly noteworthy that geomagnetic activity will increase the D-layer sunrise formation rate but decrease the D-layer sunset dissipation rate.(3)During the nighttime stage,the D-layer is generally stable and there is no obvious trend of changes over time.However,there are also fluctuations with amplitudes of about 3 km and uneven distribution in certain time periods.This study systematically and statistically analyzed the temporal and spatial characteristics of the D-layer in different time periods,revealed the impact of different geomagnetic environments on the D-layer sunrise and sunset processes,filled the gap of long-duration D-layer observation using lightning method and enriched the understanding of the academic community on the characteristics and rules of D-layer changes in low-latitude regions of East Asia.Meanwhile,the work of this paper has important practical application value for improving wireless communication and navigation systems,and can provide more accurate reference information for related modeling and prediction techniques.