Exploring the dynamic and chemical mechanisms of the formation of high altitude sporadic Na event by model

Abstract:

The high altitude sporadic Na layer events around the globe have been studied for many decades. Various studies have demonstrated that the major source of the sporadic Na layer above 100 km is the Na+ within the sporadic E layer in lower E region, where the two share very similar seasonal and local time variations. However, the neutralization process of Na+ above 100 km has not been fully understood due to lack of measurements of both neutral dynamic conditions and the model simulation that can include both dynamics and chemistry.. In this paper, we run the classic sodium model based upon the recent work by Plane et al., (2015) within a simulated lower E region, where both the ion density and the neutral atmosphere are modulated by tidal waves and gravity waves. With the formation of sporadic E layer in this simulation, our results show that the Na density change brought by tide and gravity waves can increase the Na density effectively within the sporadic E layer and the sporadic Na layer can formed above 100 km naturally, which is matched with our USU Na lidar observations.