On the role of charged aerosols in polar mesosphere summer echoes
On the role of charged aerosols in polar mesosphere summer echoes
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带电气溶胶在极地中间层夏季回波中的作用
DOI：
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发表时间：
1992
期刊：
影响因子：
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通讯作者：
M. Kelley
中科院分区：
文献类型：
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作者：
John Y. N. Cho;T. Hall;M. Kelley
极地中层和夜光云的出现证明了亚微米气溶胶存在于观测到极地中层夏季回波（PMSE）的高度。我们研究了文献中提出的带正电和带负电的气溶胶在散射过程中的作用。这些气溶胶如果带有大量电荷，可以通过双极效应提高电子施密特数，从而在 VHF 和 UHF 下产生非常高的雷达反射率。带正电的组件可能通过修饰灰尘效应增加非相干散射功率来增强 UHF 雷达散射，尽管这样的过程作为 PMSE 期间 VHF 散射的解释是不现实的。这种增强的 UHF 散射将与极窄的反向散射光谱相关。我们提出了一个模型，其中同时存在带负电和带正电的气溶胶，以解释雷达特性和带电粒子损耗的火箭探测器观测结果。最后，我们指出，扑克平地 50 MHz 长期数据与公认的动力学理论相反，显示夏季上层中间层的平均向下速度，可归因于导致 PMSE 的气溶胶的下落速度。
Submicron aerosols, as evidenced by the occurrence of polar mesospheric and noctilucent clouds, exist at heights from which polar mesosphere summer echoes (PMSE) are observed. We investigate the role of positively and negatively charged aerosols in the scattering processes proposed in the literature. These aerosols, if charged substantially, can account for the remarkably high radar reflectivity at both VHF and UHF by raising the electron Schmidt number through the ambipolar effect. A positively charged component may be responsible for enhanced UHF radar scatter by increasing the incoherent scatter power through a dressed dust effect, although such a process is not realistic as an explanation for VHF scatter during PMSE. Such an enhanced UHF scatter will be associated with extremely narrow backscatter spectra. We propose a model in which both negatively and positively charged aerosols are present to explain both the radar properties and the rocket probe observations of charged particle depletions. Finally, we point out that the Poker Flat 50-MHz long-term data, which contrary to accepted dynamical theory show average downward velocities in the summertime upper mesosphere, can be attributed to the fall speed of the aerosols responsible for PMSE.