低热层金属层及其与电离层E层耦合研究

Recently, in the mesospheric and lower thermospheric (MLT) region, a new topic about the metal layers is the "thermospheric enhaced metal layer",which is deemed as a high-altitude extension of the neutral metal layer. However, the new scientific problems are also arised, e.g., what is the source of the thermospheric enhanced metal layer? Are there general principles and features of the thermospheric enhanced metal layers? What atmosphere dynamics structure do the thermospheric enhanced metal layers reveal? What's the relationship between the thermospheric enhanced metal layers and Es, meteors? We will use the sodium lidars of different latitudes and longitudes to detect the thermospheric enhaced sodium layers. With the help of the common volume observations from the radio equipments (ionosondes, meteor radars) as well as the satellite observations, we will focus on the following topics: (1) Statistic of thermospheric enhanced metal (sodium) layers in existing data, study the distribution of them (both in latitude and longntude, time); The comparison of features between thermospheric enhanced sodium layers in the Eastern and Western Hemisphere (e.g. Beijing & Boulder) and corresponding mechanisms; (2) Analyzing the downward (or upward) phase progression to figure out whether the thermospheric enhanced sodium layers are transported or produced locally; the relationship between ions layers and thermospheric enhanced sodium layers; (3) Relationship between thermospheric enhanced sodium layer and simultaneous sporadic metal layer, as well as the relationship between the thermospheric enhanced sodium layer and Es, meteor input.

近年来，国际上对于金属层的激光雷达探测中，一个非常有意义的现象是所谓"金属层向低热层拓展（或者低热层金属层）"现象。同时，也伴生了一系列相关的科学问题，例如，低热层金属层的源是什么？低热层钠层的分布是否存在纬度差异或者东西半球差异？如果有，那么这种分布差异与流星注入、Es、大气动力学（波动）是否有关？项目从以上问题出发，通过多站点钠激光雷达的长期钠层探测资料，结合共体的电离层探测手段及卫星掩星探测资料，分析低热层钠层在不同纬度、东西半球分布的时空特性，以及与电离层Es、流星注入、大气波动之间的内在联系，试图理解低热层钠层的长期变化规律，探索其形成的机制和可能源区。

本项目针对中间层和低热层高度金属层区域的动力学、化学过程开展研究，重点瞄准金属层与电离层、低层大气的耦合过程。基于自主的激光雷达观测、结合无线电和卫星观测、以及全大气环流模式，取得了系列研究成果：（1）揭示了中间层和低热层突发金属层的形成机制，证认了电离层等离子环境通过大气波动汇聚对于中性大气可能影响，在该研究方向累积完成SCI论文6篇。（2）发现了对流层强雷暴活动对中性的金属层和金属离子层（电离层Es）的可能影响，证认了低层大气强对流活动对中高层大气的中性和电离成分的影响。在该研究方向累积完成SCI论文2篇，其中雷暴过程导致中性金属钠层增强的工作发表于Geophys.Res.Lett.，并被编辑Highlight，指出：“该工作报了新的观测（novel observation）现象，即，中层大气中性钠层在闪电后存在显著的增强，这是基于相当大量数据（a very large data set）鲁棒分析（robust analysis）后首次报道（First time）”。（3）模拟了金属层钠原子对太阳27天活动的响应，并观测到金属层高度背景大气对太阳活动引发的地磁扰动的响应，与热层大气不同，中间层顶区域大气密度与地磁活动存在明显的负相关，证实了空间因素可以作用到中高层大气，在该研究方向累积发表SCI论文6篇。. 本项目按照计划书的要求执行，累计发表标注SCI论文14篇，其中第一和通讯作者论文12篇；目前，正在投稿SCI论文1篇。项目执行期间培养博士毕业生4名（易稳、贾铭蛟、曾炫云、于秉坤）；在读硕士研究生2人，博士研究生3人、博士后3人。

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