On the abundance of metal ions in the lower ionosphere
On the abundance of metal ions in the lower ionosphere
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DOI：
10.1029/97ja00384
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发表时间：
1997-05-01
影响因子：
2.8
通讯作者：
Kopp, E
中科院分区：
文献类型：
--
作者：
Kopp, E
本文介绍了用磁质谱仪在五次火箭飞行中现场测量的低电离层金属离子Fe ~+、Mg ~+、Ca ~+和Na ~+的高度分布。在没有特别流星雨活动的时期，电离金属柱的平均总密度在4.4 ± 1.2 × 10（9）cm（-2）以内。在1976年8月12日的英仙座流星雨期间，柱密度增加了一个数量级。在所有五个航班中占主导地位的金属离子是Fe+。其在五个飞行中的柱密度平均比Mg+大2.0+/-0.6倍。将Ni+、Al+、Ca+、Mg+、K+和Na+的柱密度（归一化为Fe+）与I型碳质方解石（CI）中的相应比率进行比较，结果表明铝（80%）、钙（65%）、镁（55%）和镍（35%）的丰度减少。在95公里以上的高度，所有考虑中的金属应主要以离子的形式出现，并且从主要的损失过程，即金属离子层的向下运动，预计不同离子化金属之间没有明显的质量分馏。因此，Al、Ca、Mg和Ni的丰度降低很可能是源自部分熔融的微陨石和相关联的部分蒸发保持元素的分馏的效果，所述部分蒸发保持元素与Fe相比具有相对高的冷凝温度，Ni、Al、Ca和Mg的情况就是如此。
Height profiles of the metal ions Fe+, Mg+, Ca+, and Na+ in the lower ionosphere measured in situ in five rocket flights with a magnetic mass spectrometer are presented. The mean total column density of the ionized metals is within 4.4+/-1.2x10(9) cm(-2) in periods without special meteor shower activity. The column density increased by 1 order of magnitude during the Perseid meteor shower of August 12, 1976. The dominant metal ion in all five flights is Fe+. Its column density in the five flights is, in average, a factor 2.0+/-0.6 larger than Mg+. A comparison of the column densities of Ni+, Al+, Ca+, Mg+, K+, and Na+, which were normalized to Fe+, to the corresponding ratios in carbonaceous chondrites type I (CI) showed a depletion in the abundance of aluminium (80%), calcium (65%), magnesium (55%), and nickel (35%). At the heights above 95 km all metals under consideration should predominantly occur as ions, and no distinct mass fractionation between the different ionized metals is expected from the main loss process, the downward movement of the metal ion layers. The reduced abundance of Al, Ca, Mg, and Ni is therefore most likely an effect of a fractionation originating from partially melted micrometeorites and an associated partial evaporation retaining elements having a relatively high condensation temperature as compared to Fe, which is the case for Ni, Al, Ca, and Mg.