Photoelectron‐induced waves: A likely source of 150 km radar echoes and enhanced electron modes
Photoelectron‐induced waves: A likely source of 150 km radar echoes and enhanced electron modes
复制标题
光电子感应波：150 公里雷达回波和增强电子模式的可能来源
DOI：
10.1002/2016gl068179
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发表时间：
2016
影响因子：
5.2
通讯作者：
Y. Dimant
中科院分区：
文献类型：
--
作者：
M. Oppenheim;Y. Dimant
地磁赤道附近的甚高频雷达在白天接收到130和160公里高度之间等离子体密度不规则性的相干反射。尽管研究人员在50多年前首次发现了这些150公里的回波，并利用它们来监测垂直等离子体漂移，但产生它们的潜在机制仍然是一个谜。本文使用大规模动力学模拟来证明光电子可以驱动电子波，然后增强雷达可以观察到的150公里回波的离子密度不规则性。这个模型解释了为什么150公里的回波只在白天存在，以及为什么它们出现在中午附近的最低高度。它预测了Chau（2004）观察到的光谱结构，并提出了可以进一步评估这种机制的观测结果。它还显示了光电子波相互作用在磁化等离子体中产生的电子模式的类型和强度。
VHF radars near the geomagnetic equator receive coherent reflections from plasma density irregularities between 130 and 160 km in altitude during the daytime. Though researchers first discovered these 150 km echoes over 50 years ago and use them to monitor vertical plasma drifts, the underlying mechanism that creates them remains a mystery. This paper uses large‐scale kinetic simulations to show that photoelectrons can drive electron waves, which then enhance ion density irregularities that radars could observe as 150 km echoes. This model explains why 150 km echoes exist only during the day and why they appear at their lowest altitudes near noon. It predicts the spectral structure observed by Chau (2004) and suggests observations that can further evaluate this mechanism. It also shows the types and strength of electron modes that photoelectron‐wave interactions generate in a magnetized plasma.