Wave-vector-resolved Study of Lightning Whistler Propagation and Energetics in the Low-latitude Plasmasphere

低纬度等离子体层中闪电哨声传播和能量的波矢量解析研究

• 批准号: 1443011
• 负责人: Abram Jacobson
• 金额: $ 44.63万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-15 至 2019-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1443011&HistoricalAwards=false
• 关键词: Wave; vector; resolved; Study; Lightning

Lightning strikes on Earth generate bursts of radio waves called whistlers that can travel upwards into space and scatter high-energy electrons into the atmosphere causing losses from the trapped radiation belts. When these whistlers are generated, they typically become trapped between the conducting surface of the Earth and the lower ionosphere, the Earth-ionosphere wave-guide, and can be observed thousands of kilometers away from the original lightning strikes. If they strike the ionosphere at the correct angle though, whistlers can pass though the Earth-ionosphere wave-guide and move upward. This is believed to occur mostly at high latitudes dropping in significance approaching the low-latitude ionosphere and ceasing near the magnetic equator. Whistlers moving upward from low latitudes will interact with the inner radiation belt, those moving upward at higher latitudes with the outer radiation belt. Recent observations imply that more whistlers actually enter the ionosphere at low latitudes than previously believed but the reasons are not understood. The goal of this proposal is to assess the influence of lightning-generated whistlers on the low-latitude inner radiation belt. It has recently become apparent that understanding this process and others that control radiation belt intensity is important for national security. A high-altitude nuclear explosion is estimated to enhance the radiation belts by a factor of 1,000 to 10,000 destroying satellites in low and medium Earth orbit in a matter of weeks to months and crippling critical societal infrastructures. A detailed knowledge of the radiation belts will enable the design of technologies to potentially mitigate such hostile enhancements. This project enables the training and mentoring of a graduate student at the University of Washington contributing to the creation of the next generation of scientists.The specific technological approach in the proposed work is novel. An extensive database of 3-channel electric field observations taken at +/- 26 degrees latitude by the C/NOFS satellite will be analyzed to extract information on the wave vectors, polarization and Poynting flux of the whistlers. Normally, this would require observations of both the wave electric and magnetic field vectors. However, by making the reasonable assumption of no wave electric field along the direction of the background magnetic field, this information can be extracted from the wave electric field observations alone. Once the wave vector is calculated in this way, it will be used as input to a chain of modeling tools to trace the whistler backwards from the satellite to the source lightning in the lower ionosphere and then compared to observations at that location from a ground-based lightning detection network.

地球上的闪电会产生称为哨声的无线电波爆发，这些无线电波可以向上传播到太空并将高能电子散射到大气中，从而导致被捕获的辐射带造成损失。 当这些哨声产生时，它们通常被困在地球的导电表面和较低的电离层（地球-电离层波导）之间，并且可以在距离原始雷击数千公里的地方观察到。 如果哨声以正确的角度撞击电离层，它们就可以穿过地球-电离层波导并向上移动。 据信，这种情况主要发生在高纬度地区，接近低纬度电离层时显着性下降，并在磁赤道附近停止。从低纬度向上移动的哨声将与内辐射带相互作用，而在高纬度向上移动的哨声将与外辐射带相互作用。 最近的观察表明，实际上进入低纬度电离层的哨声数量比之前认为的要多，但原因尚不清楚。该提案的目标是评估闪电产生的哨声对低纬度内辐射带的影响。 最近很明显，了解这一过程和其他控制辐射带强度的过程对于国家安全非常重要。 据估计，高空核爆炸会使辐射带增强 1,000 至 10,000 倍，在几周到几个月内摧毁低地球和中地球轨道上的卫星，并破坏重要的社会基础设施。 对辐射带的详细了解将使技术设计能够潜在地减轻这种敌对的增强。 该项目能够对华盛顿大学的一名研究生进行培训和指导，为培养下一代科学家做出贡献。拟议工作中的具体技术方法是新颖的。 将分析 C/NOFS 卫星在纬度+/-26 度处进行的 3 通道电场观测的广泛数据库，以提取有关哨声的波矢量、极化和坡印廷通量的信息。 通常，这需要观测波电场矢量和磁场矢量。然而，通过合理假设沿背景磁场方向没有波电场，可以仅从波电场观测中提取该信息。 一旦以这种方式计算出波矢量，它将被用作一系列建模工具的输入，以从卫星向后追踪哨声到较低电离层中的闪电源，然后与地面闪电探测网络在该位置的观测结果进行比较。