2011年5月26日北京上空TeSL与Es、大气风场的同时观测

Simultaneous measurements of TeSL,Es layer and atmospheric wind in Beijing,China(116.0°E,40.5°N) on 26 May 2011

本文报道了北京延庆(116.0°E,40.5°N)钠荧光激光雷达在2011年5月26日夜间观测到的一例低热层钠层(lower thermospheric-enhanced sodium layer,TeSL)事例,从数据采集开始到观测结束,该低热层钠层持续存在且不断增强,峰值密度从250 cm^(-3)增加至1500 cm^(-3),峰值高度却从111 km逐渐下降到100 km.同一时间相距28 km的测高仪也观测到了出现在106～117 km的Es层,平均强度4.5 MHz;对流星雷达设备观测到的75～100 km的纬向风风速进行拟合,得到100～125 km的风速,风剪切节点从122 km下降到108 km.Es层和纬向风剪切节点的演化趋势与TeSL事件呈现出极好的相关性.我们计算了离子垂直速度及辐射复合反应的生成率,对钠原子的出现高度和密度做出解释,推测风剪切汇聚的Na^+与Es层中的电子中和,是形成当日TeSL的主要机制.

We report a lower thermospheric-enhanced sodium layer （TeSL） case observed at Yanqing station in Beijing, China （116.0°E,40.5°N） on 26 May 2011. From starting to collect data to the end of the observation, the density of lower thermospheric sodium layer was constantly enhanced. Its peak density increased from 250 cm-3 to 1500 cm-3. However, its peak height decreased from 111 km to 100 km gradually. At the same time, an ionosonde away from 28 km detected a Es layer in 106 km to 117 km, The average intensity of the Es layer was 4.5 MHz. According to the observational data of meteor radar, we fitted zonal wind over 100 km, and found the wind shear node decreased from 122 km to 108 km. The evolution trend of the Es layer and zonal wind were similar to the TeSL.We calculated vertical velocity of ions and the production rate of radiative recombination, and explained the density and height of the sodium atoms. We speculate the Na＋ converged by wind shear mechanism. Furthermore, the thermospheric sodium layers are neutralized from converged Na＋ layers.