Simultaneous lidar observations of the sporadic Ni layer and sporadic Na layer in the MLT

Here we report on simultaneous lidar observations of sporadic Ni (Nis) layers and sporadic Na (Nas) layers in the atmosphere over Yanqing, Beijing (40.42°N, 116.02°E) from April 2019 to October 2022. During 343 nights of observation, 68 Nis and 56 Nas were observed. The seasonal variation of Nis and Nas was also obtained, with the highest occurrence of Nis being in July (43%) and that of Nas being in June (61%). We found that the seasonal variation of Nis is similar to that of Nas and that both occur more frequently in summer than in winter. In addition, we found 23 events in which Nis and Nas occur simultaneously. The average peak altitude of Nas is approximately 1 km higher than that of Nis, and the peak density ratio of Nas to Nis is approximately 5, which is half the density ratio of the two main layers. Additionally, the strength factor for Nas is smaller than that for Nis. Through data analysis of sporadic E layers (Es), we found that Nis and Nas has a significant correlation with Es. The neutralization rates of Ni⁺/Na⁺ were calculated according to the dissociative recombination reaction of Ni⁺/Na⁺ and the WACCM-Ni (Whole Atmosphere Community Climate Model of Ni). The production rates of Ni and Na were estimated to be approximately 1:4.4, which is consistent with the density ratio of Nis to Nas. The results showed that the neutralization reaction of Ni⁺, Na⁺, and electrons in Es is the main reason for the formation of the Nis layer and the Nas layer.