Ice iron/sodium film as cause for high noctilucent cloud radar reflectivity
Ice iron/sodium film as cause for high noctilucent cloud radar reflectivity
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DOI：
10.1029/2008jd009927
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发表时间：
2008-08-26
影响因子：
4.4
通讯作者：
Bellan, P. M.
中科院分区：
文献类型：
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作者：
Bellan, P. M.
[1]夜光云是位于85公里高空的微小的带电冷冰粒，具有极高的雷达反射率。它表明，这可以解释观察到的高雷达反射率假设冰粒被一层薄的金属膜，大量的证据表明，存在这样一个膜，是由铁和钠原子的沉积在冰粒上的铁和钠层位于紧接在冰粒云层上方。冰粒表面的金属薄膜中的传导电子数很大。当在大量冰粒所占据的体积上进行平均时，这些金属膜电子的散射对雷达反射率的贡献比数量少得多的尘埃等离子体电子或电子空穴大得多。使用的观测表明，冰碛云是夏季的铁和钠层的主要汇，它表明，一个足够厚的金属层应形成一个典型的冰粒在几个小时到几天。
[1] Noctilucent clouds, tiny cold electrically charged ice grains located at about 85 km altitude, exhibit anomalously high radar reflectivity. It is shown that this observed high radar reflectivity can be explained by assuming the ice grains are coated by a thin metal film; substantial evidence exists indicating that such a film exists and is caused by the deposition of iron and sodium atoms on the ice grain from iron and sodium layers located immediately above the noctilucent cloud layer. The number of conduction electrons in the thin metal film coating an ice grain is very large. When averaged over the volume occupied by a large number of ice grains, the quivering of these metal film electrons provides a much larger contribution to radar reflectivity than does the much smaller number of dusty plasma electrons or electron holes. Using observations indicating that noctilucent clouds are the dominant sink for the summer-time iron and sodium layers, it is shown that a sufficiently thick metal layer should form on a typical ice grain in a few hours to a few days.