中层顶金属层的观测与模式研究
发布时间：2018-08-28 20:44
【摘要】：本文旨在研究中层顶金属层的行为特征和变化规律背后蕴藏的物理机制,重点研究了中层顶金属物质的源——流星消融——对金属层的潜在影响。并尝试解释了目前金属层中一些尚无定论或尚存争议的问题。本文主要研究内容如下： 1通过武汉(30°N)在过去几年内的长期Na和Fe激光雷达测量,我们展示了高高度偶发金属原子层的季节／周年变化特征。我们发现出现在105 km以上的高高度偶发Na层和偶发Fe层几乎只出现在夏季。从形态上看,它们具有较长的持续时间(几个小时)和较宽的层宽(明显超过2 km)。在少数夜晚,它们的绝对峰值密度可以相比或甚至超过相应的主层峰值密度。在并未排除所有包含偶发层剖面的情况下,我们建立了30°N的Na和Fe原子密度随月份和高度分布的等值线图。从图上可以看到,Na和Fe层同时具有明显的夏季层顶密度延伸,这与早期其它纬度的K和Ca层观测结果一致。由于这些观测代表了不同的金属种类、不同的地理位置和不同的测量年份,平均金属原子层密度的夏季层顶延伸可能代表了一个普适现象。通过我们的研究发现,这个现象是由105 km以上的高高度偶发金属原子层引起的。 2使用共振荧光雷达,我们在武汉(30.5°N,114.4°E)于2001年(Na)和2004年(Na和Fe)狮子座流星雨期间开展了金属层的观测。2001年11月18-19日出现的流星雨强爆发导致我们捕捉到了一个强的Na原子流星尾迹。然而,观测发现流星雨的消融不太可能造成Na原子柱密度的提升。三年后的同一个夜晚,在较为平静的2004年狮子座流星雨期间,我们没有捕捉到尾迹但却看到了复杂的偶发金属层。偶发Na和Fe层于狮子座流星雨辐射点升上地平面后出现在95 km高度附近。比较发现,92 km以上Na和Fe原子的柱密度过午夜后均出现明显提升。同时,该晚Na和Fe原子柱密度相比前一晚要大得多。在狮子座期间的总共四个观测夜晚里,有三个夜晚出现了类似的偶发层。它们具有相似的出现时间、出现高度和高度变化。当前的彗星理论认为狮子座流星雨除了包含能够产生可见流星的流星体还包括了微流星。以此我们认为地球在2004年狮子座流星雨期间可能遭遇到了密集的小尺度微流星体群,它们也隶属于狮子座流星雨。这些微流星体的质量通量可能比可视流星雨大得多。 3我们建立了包含电荷过程和溅射作用的单个流星体消融模型。通过该模型可以模拟出单个流星体消融出来的金属原子和离子各自随高度的分布。同时,还建立了流星尾迹的质量与温度变化模型。这些模型为研究流星消融与金属层的关系提供了基础。基于可靠的偶发流星源的参数,我们模拟了中间层和低热层区域由偶发流星提供的金属原子平均注入的时间变化。并惊奇地发现模拟的金属原子注入与多个不同纬度观测的金属原子密度在一定条件下展示了相似的年平均周日变化和周日平均季节变化规律。鉴于目前已知的因素均不能解释金属原子的年平均周日变化,我们做如下猜测：一些短生命周期的原子(不长于几个小时)决定了金属原子密度的平均周日变化,而其它传统的长生命周期原子(约几天)提供了一个近似恒定的背景密度。两种原子共同组成了我们的金属层。很明显,这些预测存在的短生命周期原子需要一个快速的汇,且其主要作用于新消融不久的金属原子。这个汇的机制还不清楚但可能和消融产生的高温有关。
[Abstract]:The purpose of this paper is to study the behavioral characteristics and the underlying physical mechanism of the metal layer at the top of the mesopause, with emphasis on the potential impact of the source of the metal material at the top of the mesopause, meteor ablation, on the metal layer. Some problems in the metal layer that are not yet conclusive or controversial are also explained.
1. Through the long-term Na and Fe lidar measurements in Wuhan (30 degrees N) over the past few years, we show the seasonal/annual variations of the high-altitude accidental metallic atomic layer. We find that the high-altitude accidental Na and Fe layers occurring above 105 km occur almost exclusively in summer. In a few nights, their absolute peak densities can be compared with or even exceed the corresponding peak densities of the main layer. Without excluding all the contour profiles containing the accidental layer, we have established an isogram of the distribution of the density of Na and Fe atoms at 30 degrees N with the month and height. It is found that both Na and Fe layers have obvious summer apex density extensions, which are consistent with the observations of K and Ca layers at other latitudes in the early years. Because these observations represent different metal species, different geographical locations and different measuring years, the summer apex extension of average metal atomic layer density may represent a universal phenomenon. Our research has found that this phenomenon is caused by high atomic height of 105 km.
2. Using resonance fluorescence radar, we observed the metal layer during the 2001 (Na) and 2004 (Na and Fe) Leonid meteor showers in Wuhan (30.5 degrees N, 114.4 degrees E). A strong meteor shower eruption on Nov. 18-19, 2001 led to the capture of a strong Na atom meteor wake. However, observations found that the melting of the meteor shower was unlikely. Three years later, during the quieter 2004 Leonid meteor shower, we did not catch the wake but saw a complex episodic metal layer. The episodic Na and Fe layers appeared near 95 km above the Leonid meteor shower's radiation level. The column densities of e atoms increased significantly after midnight. At the same time, the column densities of Na and Fe atoms were much higher that night than the previous night. The Leonid meteor shower includes micrometeors as well as meteoroids capable of producing visible meteors. So we think that during the 2004 Leonid meteor shower, the Earth may have encountered dense clusters of small-scale micrometeoroids, which are also part of the Leonid meteor shower. These micrometeoroids may have a greater mass flux than the visible meteor shower. Many.
3. A single meteor ablation model including charge process and sputtering effect is established. The model can simulate the distribution of metal atoms and ions with the height of a single meteor. Meanwhile, the mass and temperature models of meteor wakes are also established. These models are used to study the relationship between meteor ablation and metal layer. Based on the parameters of reliable accidental meteor sources, we simulated the time variation of the average injection of metal atoms by accidental meteors in the middle and lower thermospheres, and were surprised to find that the simulated metal atom injection exhibited a similar year under certain conditions with the density of metal atoms observed at different latitudes. Since the known factors do not account for the annual average diurnal variation of metal atoms, we speculate that some short-lived atoms (not longer than a few hours) determine the average diurnal variation in the density of metal atoms, while other conventional long-lived atoms (not longer than a few hours) The two atoms make up our metal layer together. Obviously, these predicted short-lived atoms require a rapid sink, which acts mainly on newly melted metal atoms. The mechanism of the sink is unclear but may be related to the high temperature produced by the melting.
【学位授予单位】：武汉大学
【学位级别】：博士
【学位授予年份】：2010
【分类号】：P185.82
本文编号：2210565
[Abstract]:The purpose of this paper is to study the behavioral characteristics and the underlying physical mechanism of the metal layer at the top of the mesopause, with emphasis on the potential impact of the source of the metal material at the top of the mesopause, meteor ablation, on the metal layer. Some problems in the metal layer that are not yet conclusive or controversial are also explained.
1. Through the long-term Na and Fe lidar measurements in Wuhan (30 degrees N) over the past few years, we show the seasonal/annual variations of the high-altitude accidental metallic atomic layer. We find that the high-altitude accidental Na and Fe layers occurring above 105 km occur almost exclusively in summer. In a few nights, their absolute peak densities can be compared with or even exceed the corresponding peak densities of the main layer. Without excluding all the contour profiles containing the accidental layer, we have established an isogram of the distribution of the density of Na and Fe atoms at 30 degrees N with the month and height. It is found that both Na and Fe layers have obvious summer apex density extensions, which are consistent with the observations of K and Ca layers at other latitudes in the early years. Because these observations represent different metal species, different geographical locations and different measuring years, the summer apex extension of average metal atomic layer density may represent a universal phenomenon. Our research has found that this phenomenon is caused by high atomic height of 105 km.
2. Using resonance fluorescence radar, we observed the metal layer during the 2001 (Na) and 2004 (Na and Fe) Leonid meteor showers in Wuhan (30.5 degrees N, 114.4 degrees E). A strong meteor shower eruption on Nov. 18-19, 2001 led to the capture of a strong Na atom meteor wake. However, observations found that the melting of the meteor shower was unlikely. Three years later, during the quieter 2004 Leonid meteor shower, we did not catch the wake but saw a complex episodic metal layer. The episodic Na and Fe layers appeared near 95 km above the Leonid meteor shower's radiation level. The column densities of e atoms increased significantly after midnight. At the same time, the column densities of Na and Fe atoms were much higher that night than the previous night. The Leonid meteor shower includes micrometeors as well as meteoroids capable of producing visible meteors. So we think that during the 2004 Leonid meteor shower, the Earth may have encountered dense clusters of small-scale micrometeoroids, which are also part of the Leonid meteor shower. These micrometeoroids may have a greater mass flux than the visible meteor shower. Many.
3. A single meteor ablation model including charge process and sputtering effect is established. The model can simulate the distribution of metal atoms and ions with the height of a single meteor. Meanwhile, the mass and temperature models of meteor wakes are also established. These models are used to study the relationship between meteor ablation and metal layer. Based on the parameters of reliable accidental meteor sources, we simulated the time variation of the average injection of metal atoms by accidental meteors in the middle and lower thermospheres, and were surprised to find that the simulated metal atom injection exhibited a similar year under certain conditions with the density of metal atoms observed at different latitudes. Since the known factors do not account for the annual average diurnal variation of metal atoms, we speculate that some short-lived atoms (not longer than a few hours) determine the average diurnal variation in the density of metal atoms, while other conventional long-lived atoms (not longer than a few hours) The two atoms make up our metal layer together. Obviously, these predicted short-lived atoms require a rapid sink, which acts mainly on newly melted metal atoms. The mechanism of the sink is unclear but may be related to the high temperature produced by the melting.
【学位授予单位】：武汉大学
【学位级别】：博士
【学位授予年份】：2010
【分类号】：P185.82
【参考文献】
相关期刊论文 前1条
1 ;The Third Peak of the 1998 Leonid Meteor Shower[J];Chinese Journal of Astronomy and Astrophysics;2001年03期
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