Behavior of sporadic Na layers on small time scale

Seventeen sporadic Na (Nas) layers were observed from ~150 h of the 8-s Na density profiles obtained by lidar measurements at Wuhan, China. Each of them consists of a sequence of small-timescale density enhancement bursts. The burst intensity ranges from 200 to 10,400 cm−3. The burst duration and interval vary between 16 and 112 s. The instantaneous growth and decay rates often have an order of 100 cm−3 s−1. This suggests that there exists a very rapid atom removal process corresponding to the dramatic burst density enhancement if the advection effect by large-scale wind could be ignored. These results provide a new clue for explaining the formation mechanism of sporadic metal layers.