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

该奖项旨在解决有关电离层下部（60-90公里）闪电放电影响的基本问题。闪电放电是静电场和电磁辐射最强大的来源之一，已知在电离层下部产生重大干扰。具体来说，有两种充分记录的扰动要么来自直接加热，称为早/快（E/F）事件，要么来自辐射带高能粒子的诱导轰击，称为闪电诱导电子沉淀（LEP）。由于电离层下部的环境电子密度较低，无法通过标准雷达技术直接测量，因此使用来自强大通信发射机的甚低频（VLF, 3-30 kHz）波遥感进行E/F和LEP事件的观测。VLF信号从较低的电离层反射，当电离层扰动沿路径发生时，其振幅和相位受到扰动，从而允许一种连续观测的形式。迄今为止，诊断和理解扰动物理学的努力已经产生了很大的定性结果。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VLF遥感的潜力。该项目将加强对因闪电引起的干扰而导致的导航和通信中断的预测。每个机构的早期职业pi将领导该项目，该项目还将为几名研究生和一名博士后研究员提供支持。由于VLF信号传播的复杂性和闪电放电的可变性，对VLF信号扰动引起的电离层扰动的物理性质的明确确定一直缺乏。在此工作中，通过引入以下创新来量化闪电-电离层耦合与VLF遥感的挑战：海洋闪电和重叠VLF发射机路径的战略观测。2. 2 .基于振幅和相位的双通道偏振和散射场分析。定量化闪电源光谱在电离层扰动中的作用。跨电离层传播和射线追踪数值编码的改进。

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.