Lightning Studies Based on Measurements Spanning the Ranges from Radio Frequency to Optical (including Infrared and Ultraviolet) to Gamma-Rays

雷电是一种壮观的自然现象，也是对人类生命财产的严重危害。关于闪电实际上是如何工作的一些基本问题仍然是开放的，如果不使用非传统的方法和工具，就无法回答。使用独特的高速分幅相机阵列在前所未有的宽波长范围内对闪电进行光学观测，除了传统的可见光范围外，还将在中远红外（IR）和近紫外（UV）范围内进行操作，以获得以前从未有过的闪电过程。红外图像将提供闪电通道不同部分的温度测量，紫外图像将使探测“冷”闪电过程（如电晕流光爆发）成为可能，这在确定闪电行为方面发挥着重要作用。观测将在佛罗里达盖恩斯维尔（盖恩斯维尔）的闪电观测站进行，同时记录相应的射频电磁场和穿透辐射（x射线和伽马射线）特征。预期的结果将潜在地影响异常多的领域/学科，除了闪电物理学之外，还包括（1）全球电路，其中电晕是使地球保持负电荷的关键过程之一，（2）云带电（接地的电晕可能是形成较低正电荷区域的重要因素），（3）高能大气物理（电晕流光爆发产生x射线和伽马射线），（4）防雷（有时声称电晕发射系统控制雷电终止点），及（五）雷暴警告（电晕的出现是雷暴危险的一个指标）。该项目旨在回答以下新的科学问题：（1）在与雷暴和闪电有关的各种现象中，日冕流光的作用是什么？(2)我们可以从红外线、可见光和紫外线范围内的闪电高速记录的直接比较中了解到什么？(3)哪些进程（除了附着进程）在闪电通道中创建循环？(4)+ CG和-CG之间的根本区别是什么？新的紫外线照相机的观测将首先瞄准下行先导分支的流光区和上行未连接先导分支的流光区。然后，将探索在闪电附着过程中形成的共同流光区和闪电通道电晕鞘成像的可能性。红外图像将允许清晰的成像的早期阶段的演变返回行程的过程中，这是不可能的，在可见光范围内，由于显着的光散射。此外，红外图像将用于区分处于加热和冷却过程不同阶段的先导通道网络的部分，而紫外图像将显示基本上冷的（并且在可见范围内通常无法检测到）流光形成。协同效应的结果将从同时观测这一前所未有的宽光波长范围内，这将与相应的记录RF电磁场签名和高能辐射一起进行。此外，最近观察到的闪电通道中的神秘环路将被检查，并将确定+CG表现出-CG特征的条件。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Lightning is a spectacular natural phenomenon but also a severe hazard to human life and property. A number of fundamental questions on how lightning actually works are still open and cannot be answered without the use of nontraditional approaches and tools. Optical observations of lightning in an unprecedentedly wide wavelength range using a unique array of high-speed framing cameras operating, besides the traditional visible-range, also in the medium-to-far infrared (IR) and near ultraviolet (UV) ranges will be performed to get a view of lightning processes that has never been possible before. IR images will provide a measure of temperature in different parts of the lightning channel and UV images will make it possible to detect “cold” lightning processes (such as corona streamer bursts) which play a fundamental role in determining lightning behavior. Observations will be carried out at the Lightning Observatory in Gainesville (LOG), Florida, in conjunction with recordings of corresponding radio-frequency electromagnetic field and penetrating radiation (x-rays and gamma-rays) signatures. The anticipated results will potentially impact an unusually large number of areas/disciplines, including, besides the lightning physics, (1) the global electric circuit, in which corona is one of the key processes that keep the Earth negatively charged, (2) cloud electrification (corona at ground may be a significant contributor to the formation of the lower positive charge region), (3) high-energy atmospheric physics (corona streamer bursts produce x- and gamma-rays), (4) lightning protection (corona-emitting systems sometimes are claimed to control the lightning termination point), and (5) thunderstorm warning (occurrence of corona is an indicator of thunderstorm hazard).The project is aimed at answering the following new science questions: (1) What is the role of corona streamers in the various phenomena associated with thunderstorms and lightning? (2) What can we learn from direct comparison of high-speed recordings of lightning in the IR, visible, and UV ranges? (3) What processes (besides the attachment process) create loops in the lightning channel? (4) How fundamental are the differences between +CGs and –CGs? Observations with the new UV camera will first target the streamer zone of descending leader branches and that of upward unconnected leaders. Then, the possibility of imaging the common streamer zone formed during the lightning attachment process and the lightning channel corona sheath will be explored. IR images will allow clear imaging of the evolution of the early stage of return-stroke process, which is impossible in the visible range due to significant light scattering. Also, IR images will be used to distinguish between parts of the leader channel network that are at different stages of their heating and cooling processes, while UV images will show essentially cold (and generally undetectable in the visible range) streamer formations. Synergistic results will be obtained from simultaneous observations in this unprecedentedly wide optical wavelength range, which will be performed in conjunction with the corresponding recordings of RF electromagnetic field signatures and energetic radiation. Further, the recently observed mysterious loops in the lightning channel will be examined and conditions under which +CGs exhibit features characteristic of –CGs will be identified.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.