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Modelling of positively charged aerosols in the polar summer mesopause region

机译：夏季极地绝经区带正电的气溶胶模型

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We present a model based analysis of rocket borne common volume measurements of electron number densities and aerosol charge densities during the ECHO campaign in 1994. During that campaign a sounding rocket was launched into a noctilucent cloud (NLC) as detected by a ground based lidar. At NLC altitudes a particle impact detector gave strong evidence for positively charged aerosols, and an electron probe measured a significant electron enhancement. We have applied a model of aerosol charging to these measurements and find that the existence of positively charged aerosols can be explained if they mainly consist of a substance with a sufficiently low work function. The electron enhancement as well as the aerosol size and number density deduced from our model are consistent with the electron probe and lidar measurements, respectively. Considering the photoelectrical properties of various metals we conclude that only sodium and potassium have a sufficiently low work function to allow for significant photoemission. Even under very favourable conditions the maximum positive charge accumulated on the aerosols is only approximately 4 elementary charges which is much less than discussed in some of the current theories for the creation of polar mesosphere summer echoes. We note that the amount of sodium of potassium required to form these particles is far above the natural abundances at NLC altitudes. The exact abundance and composition of the aerosols need to be known at the time of the in situ measurements in order to make more sophisticated comparisons between measurements and models.
机译：我们在1994年的ECHO战役中提出了基于模型的火箭载运电子体积密度和气溶胶电荷密度测量结果的模型分析。在该运动中，探空火箭被地面激光雷达探测到了夜光云（NLC）。在NLC高度，粒子撞击探测器为带正电的气溶胶提供了有力的证据，并且电子探针测量到了明显的电子增强。我们将气溶胶带电模型应用于这些测量，发现如果带正电的气溶胶主要由功函数足够低的物质组成，则可以解释其存在。由我们的模型推导的电子增强以及气溶胶尺寸和数量密度分别与电子探针和激光雷达的测量结果一致。考虑到各种金属的光电特性，我们得出结论，只有钠和钾具有足够低的功函，才能实现显着的光发射。即使在非常有利的条件下，气溶胶上累积的最大正电荷也只有大约4个基本电荷，这远小于当前一些有关建立极地中间层夏季回波的理论中所讨论的电荷。我们注意到，形成这些颗粒所需的钾钠含量远高于NLC海拔高度的自然丰度。在原位测量时，需要知道气溶胶的确切含量和组成，以便在测量和模型之间进行更复杂的比较。

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