Remote Measurements of Lightning Current and Charge Transfer with Low Frequency ElectroMagnetic (EM) Sensors

尽管进行了至少几个世纪的科学研究，闪电仍然是现代研究的一个重要而有趣的目标。对与精灵等不寻常现象有关的闪电的测量表明，闪电中的大电流和电荷转移可能比之前估计的更常见，但人们对电流和电荷转移上限、这些高能事件的地理分布及其相关的气象学知之甚少。事实上，在任何类型的闪电中，很少有人对电荷转移和持续电流进行定量测量。绝大多数闪电测量是在有限的地理区域使用短距离或局部仪器进行的，这些仪器非常适合研究个别闪电的细节，但不适合观察更广泛地区的闪电过程。在过去几年中，在开发远距离、定量闪电电流和电荷转移遥感技术方面取得了实质性进展(部分是在前身NSF赠款的支持下)。随着这些能力的基本发展，一项为期三年的研究工作将应用这些闪电遥感技术来完成与以下主题有关的重点任务：地面伽马射线闪电的机制和影响；闪电电荷转移和持续电流的基本统计数据和气象变化；风暴综合闪电电荷转移到地面的新测量；以及利用高速闪电视频和闪电测绘阵列数据分析相关的远程闪电电荷和电流测量。这些测量的智力价值在于，它们将提高我们对闪电数量变化的理解，并将识别导致异常强烈闪电的气象条件。风暴中某些类型的闪电电荷转移和持续电流特征的存在也可能提供对风暴基本电气结构和发展的洞察。将量化与地面伽马射线闪电有关的闪电的特征，从而更好地了解这一现象及其与闪电引发的可能联系。该技术方法利用了过去已经进行的实验测量，以及将使用现有仪器进行的新测量。研究具有更广泛的影响，因为它为学生提供了一个很好的培训机会，可以在数据驱动的分析、实验和硬件以及理论建模之间取得平衡。一名研究生将在该项目的支持下接受培训，杜克大学奖学金资助的本科生研究助理也将参与其中。这一领域的研究具有很高的公众知名度，因为人们对闪电及其影响有着广泛的兴趣。过去PI在这一领域的研究引起了媒体的兴趣，导致了大量的新闻稿、媒体文章，甚至两次电视露面。将尽一切努力确保尽可能广泛地传播结果。这些测量是更广泛的大气电学和大气科学界的资源，将作为国家和国际合作的一部分由多名研究人员在报告和出版物中使用。这项工作的数据将被视为社区的一种资源，并将继续提供给其他人。这些测量还具有重要的实际联系，有助于更好地了解闪电危害，并有助于更好地确定和减轻闪电对人类活动的影响。这一努力还将有助于正在进行的与Quasar公司(加利福尼亚州圣地亚哥)的合作，将其中一些闪电遥感技术商业化。

Despite at least several centuries of scientific inquiry, lightning remains an important and interesting target for modern research. Measurements of lightning associated with unusual phenomena such as sprites have anecdotally suggested that large currents and charge transfer in lightning strokes may be more common than previously appreciated, but little is known about current and charge transfer upper limits, the geographic distribution of these energetic events, and their associated meteorology. In fact, few quantitative measurements of charge transfer and continuing currents have been made in lightning of any kind. The overwhelming majority of lightning measurements have been made in limited geographic areas with short range or local instrumentation that are ideal for studying the details of individual flashes, but not for observing lightning processes over wider regions. Substantial progress over the past several years (partly with support of a predecessor NSF grant) has been made in developing techniques for long range, quantitative lightning current and charge transfer remote sensing. With these capabilities now essentially fully developed, a three-year research effort will apply these lightning remote sensing techniques to complete focused tasks related to the following topics: the mechanisms behind and implications of terrestrial gamma ray flashes; the basic statistics and meteorological variability of lightning charge transfer and continuing currents; novel measurements of the total storm-integrated lightning charge transfer to ground; and the analysis of correlated remote lightning charge and current measurements with high speed lightning video and lightning mapping array data.The intellectual merit of the measurements is that they will improve our understanding of the quantitative variability of lightning, and they will identify the meteorological conditions responsible for unusually strong lightning. The presence of certain classes of lightning charge transfer and continuing current characteristics in storms may also provide insight into fundamental storm electrical structure and development. The characteristics of lightning associated with terrestrial gamma ray flashes will be quantified, leading to a better understanding of the phenomenon and its possible link to lightning initiation. The technical approach leverages past experimental measurements that have already been made, and new measurements that will be made with existing instrumentation. This ensures the research can be completed cost-effectively.The research has broader impact in that it provides an excellent training opportunity for students with a balance of data-driven analysis, experiments and hardware, and theoretical modeling. One graduate student will be trained with support from this project, and undergraduate research assistants funded by Duke fellowships will also be involved. Research in this area has a high public profile because of broad interest in lightning and its effects. Past research in this area by the PI has generated media interest resulting in numerous press releases, media articles, and even two television appearances. Every effort will be made to ensure the broadest possible dissemination of the results. The measurements are a resource to the broader atmospheric electricity and atmospheric science communities and will be used in presentations and publications by multiple investigators as part of national and international collaborations. Data from the effort will be treated as a resource to the community and will continue to be made available to others. The measurements also have significant practical links to better understanding lightning hazards and could help better identify and mitigate the impact of lightning on human activities. The effort will also aid an ongoing collaboration to commercialize some of these lightning remote sensing techniques with QUASAR, Inc. (San Diego, CA).