Lower thermospheric‐enhanced sodium layers observed at low latitude and possible formation: Case studies
Lower thermospheric‐enhanced sodium layers observed at low latitude and possible formation: Case studies
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DOI：
10.1002/jgra.50200
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发表时间：
2013-05
期刊：
影响因子：
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通讯作者：
X. Xue;X. Dou;J. Lei;Juanli Chen;Z. Ding;Tao Li;Q. Gao;W. Tang;Xuewu Cheng;K. Wei
中科院分区：
文献类型：
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作者：
X. Xue;X. Dou;J. Lei;Juanli Chen;Z. Ding;Tao Li;Q. Gao;W. Tang;Xuewu Cheng;K. Wei
本文报道了2012年3月10日和4月10日在中国丽江低纬站（26.7°N，100.0°E）观测到的两个低热层增强钠层（TeSL）个例。这两个案例中的TeSL分别位于122和112公里附近的高度。此外，2012年3月10日观测到的TeSL伴随着100公里附近的强零星钠层。TeSL和SSL都表现出潮汐诱导的向下运动。邻近的地面和空间电离层射电观测表明，在TeSL出现之前，存在较强的Es层，表明通过潮汐风切变机制形成了“Es-TeSL（SSLs）”链。在潮波垂直波长不变的情况下，发现在潮风切变引起的不同区域，TeSL的演化过程不同：（1）在潮辐合区，由于Na+寿命在低层迅速减少，TeSL/SSL向下传播相增强;（2）在离子聚散界面区，TeSL/SSL仍随潮汐下降相进行，但钠离子浓度没有明显增强;（3）当TeSL/SSL进入潮汐风辐散区时，层密度有减小的趋势。
We report two lower thermospheric‐enhanced sodium layer (TeSL) cases observed at a low‐latitude station, Lijiang, China (26.7°N, 100.0°E), on 10 March and 10 April 2012, respectively. The TeSLs in the two cases were located at altitudes near 122 and 112 km, respectively. In addition, strong sporadic sodium layers (SSLs) near 100 km accompanied the TeSL observed on 10 March 2012. Both the TeSLs and SSLs exhibited tidal‐induced downward motion. The adjacent ground‐based and space‐borne ionospheric radio observations showed strong Es layers before the appearance of the TeSLs, suggesting an “ Es– TeSLs (SSLs)” chain formed through the tidal wind shear mechanism. Assuming that the vertical tidal wavelengths remain unchanged, it is found that in different regions caused by the tidal wind shear, different TeSLs evolution processes are expected: (1) in a tidal‐convergence region, a TeSL/SSL with a downward propagation phase is enhanced due to a rapid decrease in the Na+lifetime at the lower altitude; (2) in an ion convergence‐divergence interface region, a TeSL/SSL will still follow the tidal downward phase progression, but sodium density does not exhibit evident enhancement; and (3) when a TeSL/SSL enters into a tidal wind‐divergence zone, the layer density tends to decrease.