Collaborative Research: Quantitative Analysis of Lightning's Multifaced Impact on the Ionosphere

合作研究：闪电对电离层多方面影响的定量分析

• 批准号: 1451210
• 负责人: Mark Golkowski
• 金额: $ 24.5万
• 依托单位: University of Colorado at Denver
• 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: 2015-09-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1451210&HistoricalAwards=false
• 关键词: Collaborative; Research; Quantitative; Analysis; Lightning

This award addresses fundamental questions about the impact of lightning discharges on the lower ionosphere (60-90 km). Lightning discharges are among the most powerful sources of electrostatic fields and electromagnetic radiation and are known to create significant disturbances in the lower ionosphere. Specifically, two well documented perturbations stem either from direct heating, known as Early/Fast (E/F) events, or from induced bombardment by energetic particles from the radiation belts, known as lightning-induced electron precipitation (LEP). The low ambient electron density of the lower ionosphere precludes direct measurement by standard radar techniques, hence observations of E/F and LEP events are made using remote sensing with Very Low Frequency (VLF, 3-30 kHz) waves from powerful communication transmitters. VLF signals reflect from the lower ionosphere and are perturbed in amplitude and phase when an ionospheric disturbance occurs along the path, thus allowing a form of continuous observation. Efforts to diagnose and understand the physics of disturbances have yielded largely qualitative results to date. This project will bring together two experts in ionospheric and magnetospheric processes to realize the full potential of VLF remote sensing. This project will enhance efforts to forecast navigation and communication outages due to lightning-induced disturbances. Early-career PIs at each institution will lead the project, which will also contribute to the support of several graduate students and a post-doctoral researcher. Unambiguous determination of the physics of ionospheric disturbances from VLF signal perturbations has been lacking due to the complex nature of VLF signal propagation and also the variability of lightning discharges. In this effort, the challenges to quantifying lightning-ionosphere coupling with VLF remote sensing by introducing the following innovations: 1. Strategic observations of ocean-based lightning and overlapping VLF transmitter paths. 2. Novel polarization and scattered field analysis from amplitude and phase in two channels.3. Quantifying the role of the lightning source spectrum in the ionospheric disturbance.4. Improvement of numerical codes for trans-ionospheric propagation and raytracing.

该奖项解决了有关闪电放电对低电离层（60-90 公里）影响的基本问题。闪电放电是最强大的静电场和电磁辐射源之一，已知会在较低的电离层中产生严重的干扰。具体来说，两个有据可查的扰动要么源于直接加热，称为早期/快速（E/F）事件，要么源于辐射带高能粒子的诱导轰击，称为闪电诱发电子沉淀（LEP）。较低电离层的低环境电子密度妨碍了标准雷达技术的直接测量，因此对 E/F 和 LEP 事件的观测是使用来自强大通信发射机的甚低频（VLF，3-30 kHz）波的遥感进行的。 VLF 信号从较低的电离层反射，当沿路径发生电离层扰动时，其幅度和相位会受到扰动，从而允许进行连续观测。迄今为止，诊断和理解扰动物理原理的努力已经取得了很大程度上定性的结果。该项目将汇集电离层和磁层过程方面的两位专家，以充分发挥甚低频遥感的潜力。该项目将加强对雷电干扰造成的导航和通信中断的预测工作。每个机构的早期职业 PI 将领导该项目，该项目还将为数名研究生和一名博士后研究员提供支持。由于 VLF 信号传播的复杂性以及闪电放电的可变性，一直缺乏对 VLF 信号扰动引起的电离层扰动的物理原理的明确确定。在这项工作中，通过引入以下创新来量化闪电-电离层耦合与甚低频遥感的挑战： 1. 对海洋闪电和重叠甚低频发射机路径的战略观测。 2. 从两个通道的幅度和相位进行新颖的偏振和散射场分析。3．量化雷源谱在电离层扰动中的作用。4．改进跨电离层传播和射线追踪的数字代码。