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

该奖项涉及闪电放电对低电离层(60-90公里)的影响的基本问题。闪电放电是静电场和电磁辐射最强大的来源之一，众所周知，它会在较低的电离层造成重大干扰。具体地说，有两个有充分证据的扰动要么来自直接加热，即所谓的早/快(E/F)事件，要么源于来自辐射带的高能粒子的诱导轰击，称为闪电诱导电子沉淀(LEP)。低电离层的低环境电子密度使标准雷达技术无法直接测量E/F和LEP事件，因此使用来自强大通信发射机的甚低频(VLF)波遥感来观测E/F和LEP事件。甚低频信号从较低的电离层反射，当沿路径发生电离层干扰时，VLF信号在幅度和相位上受到扰动，从而允许进行一种形式的连续观测。迄今为止，诊断和理解扰动物理学的努力基本上取得了定性结果。该项目将汇集电离层和磁层过程方面的两位专家，以充分发挥甚低频遥感的潜力。该项目将加强对闪电引起的干扰造成的导航和通信中断的预测。每个机构的早期职业经理人将领导该项目，这也将有助于支持几名研究生和一名博士后研究员。由于甚低频信号传播的复杂性以及闪电发射的多变性，缺乏对甚低频信号扰动的电离层物理性质的明确确定。在这项工作中，通过引入以下创新来量化闪电-电离层与甚低频遥感的耦合所面临的挑战：1.对海洋闪电和重叠的甚低频发射机路径进行战略观测。2.从幅度和相位两个角度对双通道的偏振和散射场进行了分析。量化闪电源谱在电离层扰动中的作用。跨电离层传播和射线追踪数值程序的改进。

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.