Sodium Lidar observed multiple sodium layer structures and their dynamical coupling mechanism

Abstract

Abstract. On the night of 13 June 2013, the University of Science and Technology of China (USTC) sodium lidar observed multiple sporadic sodium layers (SSLs) and enhanced sodium patterns (ESPs) over Hefei, China (31.8°N, 117.3°E). These structures appeared at different times, collectively spanning nearly the entire night, and exhibited distinct vertical motions and horizontal propagation behaviors. Their propagation was closely linked to the background horizontal wind, indicating the role of horizontal transport. Combined observations from the nearby meteor radar and ionosonde in Wuhan (~200 miles west of Hefei) revealed that SSLs occurring before 19:30 UT are closely associated with the sporadic E (Es) layer. The evolution of the Es layer shows an overall downward propagation consistent with tidal wind variations, suggesting that tidal waves modulate ion distribution and associated sodium production. Notably, two ESP events exhibit quasi-periodic structures with periods of ~50–60 minutes, accompanied by similar oscillations in the Es layer and associated ion convergence regions. This behavior indicates that the atmospheric gravity waves may also modulate the horizontal wind, thereby influencing ion convergence, the Es layer, and sodium density. These observations provide new insights into the roles of wave-modulated horizontal winds in driving sodium-layer variability and underscore the importance of coupled neutral–ion processes in the MLT region.