A Numerical Investigation on the Variation of Sodium Ion and Observed Thermospheric Sodium Layer at Cerro Pachón, Chile During Equinox
A Numerical Investigation on the Variation of Sodium Ion and Observed Thermospheric Sodium Layer at Cerro Pachón, Chile During Equinox
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DOI：
10.1029/2018ja025927
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发表时间：
2019-12
期刊：
影响因子：
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通讯作者：
X. Cai;T. Yuan;J. Eccles;N. Pedatella;Xiaoqi Xi;C. Ban;A. Liu
中科院分区：
文献类型：
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作者：
X. Cai;T. Yuan;J. Eccles;N. Pedatella;Xiaoqi Xi;C. Ban;A. Liu
最近使用 Na 激光雷达在低纬度和高纬度地区观测到中性钠 (Na) 层延伸至热层（长达 170 公里）。然而，其形成的地球物理机制和影响目前尚不清楚。在这项研究中，我们对低纬度 E 和 F 地区的 Na 和 Na+ 变化进行了先进的二维数值模拟。数值模拟用于研究电磁力、中性风、扩散和重力的贡献。模拟得出三个主要发现。首先，地磁赤道副热带地区的Na+是中性钠的主要储存库，在E→×B→漂移的垂直分量和库仑漂移的共同作用下，其夜间分布大多在200 km以下。其次，我们发现喷泉效应对Na在夜间的行为影响很小。第三，智利帕雄山春分时热层钠层频繁生成的可能解释是，来源不明的大型垂直风扰动产生的大型垂直中性输送，其震级超过10 m/s，与半日潮密切相关。
The extension of the neutral sodium (Na) layer into the thermosphere (up to 170 km) has recently been observed at low and high latitudes using a Na lidar. However, the geophysical mechanisms and implications of its formation are currently unknown. In this study, we conduct an advanced two‐dimensional numerical simulation of the Na and Na+ variations in the E and F regions at low latitudes. The numerical simulations are used to investigate the contributions of the electromagnetic force, neutral wind, diffusion, and gravity. The simulations lead to three major findings. First, Na+ in the subtropical region of the geomagnetic equator acts as the major reservoir of the neutral sodium, and its distribution during nighttime is mostly below 200 km due to the combined effect of the vertical component of the E→×B→ drift and Coulomb‐induced drift. Second, we find that the fountain effect has little influence on the behavior of Na in the nighttime. Third, the probable explanation for the frequent generation of the thermospheric sodium layer during spring equinox at Cerro Pachón, Chile is attributed to the large vertical neutral transport generated by large vertical wind perturbations of unknown origin, with a magnitude exceeding 10 m/s that is closely associated with the semidiurnal tide.