A review of latitudinal characteristics of sporadic sodium layers, including new results from the Chinese Meridian Project

Our results highlighted both the single-mechanism and combined actions of the temperature mechanism and ES theory on the formation of the SSLs in different latitudes and altitudes. The high latitude SSLs have a closer link with the ES theory and the subtropical SSLs correlate more strongly to high temperature, while both the temperature mechanism and ES theory probably contribute equally to the SSLs in the low-latitude Haikou station. In fact, we show that the observations in Haikou yield the example that two SSL events could be controlled by different mechanisms even though they occurred at the same location within the same night.