Observations of Thermospheric Na Layers up to 170 Km at Lijiang (26.7 N, 100.0 E)

Abstract:

We report the lidar observations of neutral Na layers in the thermosphere up to about 170 km at Lijiang in 2012. We get 4 cases with downward phase progression during whole 36 days observations. The maximum densities of these thermospheric Na layers range from 3.62 to 6.27 above 125 km. We calculate the detection limit for each case and find the densities of these layers are well above the detection limit, which makes the existence of Na layers up to so high latitudes definitely. Correlation with tides output from GSWM (Global Scale Wave Model) is also analyzed. Evidence has showed that the direct recombination Na⁺ +e^-→ Na + hν may account for the formation of neutral Na layers, similarly as the formation of neutral Fe layers analyzed in Chu et al. [2011], Fe⁺ +e^-→ Fe + hν , which is affected by the semidiurnal tides.