中層頂金屬層的觀測與模式研究
發(fā)布時間：2018-08-28 20:44
【摘要】：本文旨在研究中層頂金屬層的行為特征和變化規(guī)律背后蘊藏的物理機制,重點研究了中層頂金屬物質(zhì)的源——流星消融——對金屬層的潛在影響。并嘗試解釋了目前金屬層中一些尚無定論或尚存爭議的問題。本文主要研究內(nèi)容如下： 1通過武漢(30°N)在過去幾年內(nèi)的長期Na和Fe激光雷達測量,我們展示了高高度偶發(fā)金屬原子層的季節(jié)／周年變化特征。我們發(fā)現(xiàn)出現(xiàn)在105 km以上的高高度偶發(fā)Na層和偶發(fā)Fe層幾乎只出現(xiàn)在夏季。從形態(tài)上看,它們具有較長的持續(xù)時間(幾個小時)和較寬的層寬(明顯超過2 km)。在少數(shù)夜晚,它們的絕對峰值密度可以相比或甚至超過相應(yīng)的主層峰值密度。在并未排除所有包含偶發(fā)層剖面的情況下,我們建立了30°N的Na和Fe原子密度隨月份和高度分布的等值線圖。從圖上可以看到,Na和Fe層同時具有明顯的夏季層頂密度延伸,這與早期其它緯度的K和Ca層觀測結(jié)果一致。由于這些觀測代表了不同的金屬種類、不同的地理位置和不同的測量年份,平均金屬原子層密度的夏季層頂延伸可能代表了一個普適現(xiàn)象。通過我們的研究發(fā)現(xiàn),這個現(xiàn)象是由105 km以上的高高度偶發(fā)金屬原子層引起的。 2使用共振熒光雷達,我們在武漢(30.5°N,114.4°E)于2001年(Na)和2004年(Na和Fe)獅子座流星雨期間開展了金屬層的觀測。2001年11月18-19日出現(xiàn)的流星雨強爆發(fā)導(dǎo)致我們捕捉到了一個強的Na原子流星尾跡。然而,觀測發(fā)現(xiàn)流星雨的消融不太可能造成Na原子柱密度的提升。三年后的同一個夜晚,在較為平靜的2004年獅子座流星雨期間,我們沒有捕捉到尾跡但卻看到了復(fù)雜的偶發(fā)金屬層。偶發(fā)Na和Fe層于獅子座流星雨輻射點升上地平面后出現(xiàn)在95 km高度附近。比較發(fā)現(xiàn),92 km以上Na和Fe原子的柱密度過午夜后均出現(xiàn)明顯提升。同時,該晚Na和Fe原子柱密度相比前一晚要大得多。在獅子座期間的總共四個觀測夜晚里,有三個夜晚出現(xiàn)了類似的偶發(fā)層。它們具有相似的出現(xiàn)時間、出現(xiàn)高度和高度變化。當(dāng)前的彗星理論認為獅子座流星雨除了包含能夠產(chǎn)生可見流星的流星體還包括了微流星。以此我們認為地球在2004年獅子座流星雨期間可能遭遇到了密集的小尺度微流星體群,它們也隸屬于獅子座流星雨。這些微流星體的質(zhì)量通量可能比可視流星雨大得多。 3我們建立了包含電荷過程和濺射作用的單個流星體消融模型。通過該模型可以模擬出單個流星體消融出來的金屬原子和離子各自隨高度的分布。同時,還建立了流星尾跡的質(zhì)量與溫度變化模型。這些模型為研究流星消融與金屬層的關(guān)系提供了基礎(chǔ)�；诳煽康呐及l(fā)流星源的參數(shù),我們模擬了中間層和低熱層區(qū)域由偶發(fā)流星提供的金屬原子平均注入的時間變化。并驚奇地發(fā)現(xiàn)模擬的金屬原子注入與多個不同緯度觀測的金屬原子密度在一定條件下展示了相似的年平均周日變化和周日平均季節(jié)變化規(guī)律。鑒于目前已知的因素均不能解釋金屬原子的年平均周日變化,我們做如下猜測：一些短生命周期的原子(不長于幾個小時)決定了金屬原子密度的平均周日變化,而其它傳統(tǒng)的長生命周期原子(約幾天)提供了一個近似恒定的背景密度。兩種原子共同組成了我們的金屬層。很明顯,這些預(yù)測存在的短生命周期原子需要一個快速的匯,且其主要作用于新消融不久的金屬原子。這個匯的機制還不清楚但可能和消融產(chǎn)生的高溫有關(guān)。
[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.
【學(xué)位授予單位】：武漢大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2010
【分類號】：P185.82
本文編號：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.
【學(xué)位授予單位】：武漢大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2010
【分類號】：P185.82
【參考文獻】
相關(guān)期刊論文 前1條
1 ;The Third Peak of the 1998 Leonid Meteor Shower[J];Chinese Journal of Astronomy and Astrophysics;2001年03期
，本文編號：2210565
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