热层大气中钠原子层的激光雷达观测研究

发布时间：2017-12-27 08:53

本文关键词：热层大气中钠原子层的激光雷达观测研究　出处：《中国科学技术大学》2016年博士论文　论文类型：学位论文

【摘要】：中高层大气中的金属原子层可以被共振荧光激光雷达探测到,因而成为了探测空间大气相互作用区域的良好示踪物。中性金属原子通常被认为存在于75-110km的中间层和低热层区域,它们的这种分布特征限制了激光雷达遥感的探测范围。近些年来新的发现从根本上改变了我们的认识。Chu et al. (2011)报道了在南极McMurdo观测站(77.83°S,166.66°E)使用铁激光雷达发现的最高高度达到155 km的中性铁原子层现象(Chu et al.,2011)。这是第一次在热层大气区域发现具有重力波特征的中性铁原子层。在这之后,许多热层金属原子层的观测相继被报道出来。热层中性金属原子层为使用激光雷达技术对100-200 km中性成分进行高时空分辨率观测提供了优良的示踪物。它们可以被用来研究热层和电离层的耦合过程,以及100-200km高度的化学反应、热力学、动力学和电动力学现象。作为一个研究各种物理和化学过程的天然实验室,热层中性金属原子的研究具有重要的意义。但是截至2013年底,钠原子层的最高观测记录只为140 km,这一结果远低于铁原子层170km (Chu et al.,2013)和钾原子层155 km (Friedman et al.,2013)的观测记录。由此我们产生了一系列疑问,比如中性铁原子层170 km的观测记录是得益于McMurdo特殊的地理位置,抑或是铁原子的本身特性?中性钠原子层能否在南极以外的其他地区突破140 km的观测记录?解决这些问题有助于我们深入理解热层中性金属原子层的起源和形成机制。在本文中,我们主要对2012年3月、4月和12月在丽江(地磁纬度21.6°N,171.8°E)观测到的最高可以达到170km具有潮汐相位特征的中性钠原子层现象进行研究,并对其形成机制进行定性分析。据我们所知,这是中性钠原子层第一次在这个高度被发现。在2012年37个夜间的观测数据中,我们确认了至少12个最高高度超过130 km的丽江热层钠原子层事件,即其出现频率约为33%。热层大气中的中性钠原子层密度非常低,在130-170km之间约为1-6cm-3,比中间层顶附近的钠层峰值密度小大约3个数量级。它们都有相位向下发展演化的特征,下降速率约为11-12 km/h(约3 m/s),这一数值和140 km左右半日潮汐的垂直相速度相一致。丽江热层中性钠原子事件几乎都对应着中等或者较强的的赤道喷泉效应现象,这两者之间的关系有力的支持了我们的理论假设,即金属离子在赤道喷泉效应的作用下从赤道地区向低纬地区输运,这一过程为丽江上空的热层区域带来了Na+离子,根据Chu et al.(2011)和Yu and Chu(2014)中的理论和Tsuda et al.(2015)中的假设,我们进一步认为丽江热层钠原子层是通过潮汐风剪切汇聚的Na+离子层通过直接辐射复合反应Na++e-→Na+hv中和而形成的,并通过估算,得到了和观测相一致的结果。在本文中我们还对子午工程各台站的热层钠原子层的观测结果进行了分析,它们与丽江观测结果的差异表明了探测极限对于热层中性金属原子观测活动的重要性。通过子午工程各台站观测情况的对比,我们进一步推论,对于低纬130km以上热层金属原子层的形成过程,赤道喷泉效应引起的等离子体输运起到了非常重要的作用。丽江热层钠原子层的形成机制在低纬度地区具有代表性。
[Abstract]:The atomic layer in middle and upper atmosphere can be detected by resonance fluorescence lidar, so it becomes a good tracer for detecting the interaction area of space atmosphere. Neutral metal atoms are usually considered in the middle and low thermosphere regions of 75-110km. Their distribution limits the range of lidar remote sensing. The new discoveries have fundamentally changed our understanding in recent years. Chu et al. (2011) reported a neutral iron atomic layer phenomenon with highest altitude of 155 km (Chu et al., 2011) detected at the McMurdo Observatory (77.83 degree S, 166.66 degrees E) at the Antarctic. This is the first time to find a neutral iron layer with the characteristics of a gravitational wave in the hot layer atmosphere. After that, many observations of the metallic layer of the hot layer have been reported. The neutral metal atomic layer of the thermal layer provides a good tracer for high temporal resolution observation of the neutral component of 100-200 km using laser radar technology. They can be used to study the coupling process of the heat layer and the ionosphere, as well as the chemical reaction, thermodynamics, dynamics and electrodynamics of the 100-200km height. As a natural laboratory for the study of various physical and chemical processes, the study of the neutral metal atoms in the hot layer is of great significance. But by the end of 2013, the highest observation record of sodium atomic layer was only 140 km, which is much lower than that of atomic layer 170km (Chu et al., 2013) and potassium atomic layer 155 km (Friedman et al., 2013). We have a series of questions, such as the observation records of neutral iron atoms km layer 170 is McMurdo due to the special geographical location, or is the iron atom itself? Neutral sodium atom layer can in other areas of Antarctica exceeded 140 km observation records? To solve these problems helps us to understand the origin and the formation mechanism of thermospheric neutral metal atoms layer. In this paper, we mainly studied the phenomenon of neutral sodium atomic layer with the highest tidal phase characteristics observed at Lijiang (geomagnetic latitude 21.6 degree N, 171.8 degree E) in March 2012, April and December, and qualitatively analyzed its formation mechanism. As far as we know, this is the first time that the neutral sodium layer is found at this height. During the 37 night observations in 2012, we identified at least 12 layers of sodium layer events in Lijiang hot layer with a maximum height of more than 130 km, that is, the occurrence frequency is about 33%. The density of neutral sodium layer in the thermosphere is very low, and it is about 1-6cm-3 between 130-170km, which is about 3 orders of magnitude smaller than the peak density of the sodium layer near the top of the middle layer. They all have the characteristics of downward evolution of the phase. The descending rate is about 11-12 km/h (about 3 m/s), which is consistent with the vertical velocity of 140 km or half day tide. Lijiang thermospheric neutral sodium atomic events almost corresponds to a moderate or strong equatorial fountain effect, the relationship between the strong support of our hypothesis, the metal ions in the equatorial fountain effect from the equator to the low latitude area transport layer, heat the process over Lijiang area bring the Na+ ion, according to Chu et al. (2011) and Yu and Chu (2014) in the ET al. theory and Tsuda (2015) in the hypothesis, we further consider the Lijiang hot layer sodium layer through the Na+ layer of ion wind shear convergence tide through direct radiative recombination reaction of Na++e-, Na+hv and formed and, by estimating, are consistent with the observation results. In this paper, we also analyze the observational results of the sodium layer in the hot layer of every station in the meridian project. The difference between them and the observations in Lijiang indicates the importance of the detection limit for the observation of the neutral metal atoms in the thermal layer. By comparing the observational results of different stations in the meridian project, we further conclude that for the formation of the atomic layer of the hot layer above 130km above the low latitude, the plasma transport caused by the equatorial fountain effect has played a very important role. The formation mechanism of the sodium atomic layer of the Lijiang thermal layer is representative at low latitudes.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P407

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