Remote Lightning Current and Charge Measurements

尽管经过几个世纪的科学探索，闪电的许多基本科学方面仍然没有完全理解。 地面伽马射线闪光（TGFs）表明，失控击穿在至少一些闪电的开始或发展中起着作用，但这种联系的细节仍然难以捉摸。含有大量电荷转移的高能闪电具有重要的实际后果，例如森林火灾和建筑物损坏，但产生它们的闪电和风暴的种类通常不为人所知。 近年来，在发展远程雷电流和电荷遥感技术方面取得了实质性进展，这些技术可以帮助回答这些和其他重要的科学问题。这项研究工作将应用这些雷电流和电荷遥感技术完成与以下主题有关的几项重点任务：陆地伽马射线闪光背后的机制和含义;雷击参数和闪电特征之间的联系（特别是在异常活跃的中风）;和新的测量雷暴云电荷密度，充电率，和净雷暴电荷转移闪电。这些任务涉及宽带低频无线电测量和闪电测绘阵列（LMA）数据的联合分析，这是一种互补测量的组合，其价值已在研究小组最近的工作中得到证明。 智力优点：最近的测量首次揭示了TGFs背后的过程，目前的项目旨在确定产生TGFs的闪电的不寻常之处，并量化负责的过程。这将使雷暴中失控击穿的真实建模成为可能，并有助于确定与闪电引发的任何联系。 人们对雷击电流和电荷之间的定量联系以及闪电的细节知之甚少，特别是在不寻常的或高能的雷击中，这项工作将提供这种新的基本理解。 新的测量净雷暴电荷转移和电荷密度在雷暴在广泛的条件下，也将提供新的界限，这些参数与驱动电荷分离的过程，在雷暴。 该技术方法应用了宽带无线电和LMA测量联合分析的强大技术。 它还建立在现有数据或新数据的基础上，大部分现有仪器，这确保了项目可以尽可能经济高效地完成。更广泛的影响：该研究为学生提供了一个极好的培训机会，可以平衡数据驱动的分析，实验和硬件，以及理论建模。 一名研究生将在研究的支持下接受培训，内部资助的本科研究助理也将参与其中。 最近的本科生参与导致了第一作者出版物的学生和研究生研究助理在闪电领域。 由于人们对闪电及其影响的广泛兴趣，这一领域的研究具有很高的公众形象。 PI过去在这一领域的研究引起了媒体的兴趣，导致了许多新闻稿，媒体文章和电视采访。 NSF的支持对于保持支持这种与公众接触的能力至关重要。 这些测量结果是更广泛的大气电和大气科学界的一个资源，并已被许多研究人员作为国家和国际合作的一部分用于演示和出版物。 这些测量结果还与雷电灾害探测有着重要的实际联系，可以帮助更好地识别和减轻其影响。

Despite centuries of scientific inquiry, many fundamental scientific aspects of lightning are still not fully understood. Terrestrial gamma ray flashes (TGFs) indicate that runaway breakdown plays a role in the initiation or development of at least some lightning, but details of this connection remain elusive. Energetic lightning containing significant charge transfer has important practical consequences, such as forest fires and damage to structures, but the kinds of lightning flashes and storms that create them are not in general known. Substantial progress has been made recently in developing techniques for long range lightning current and charge remote sensing that can help answer these and other important scientific questions.This research effort will apply these lightning current and charge remote sensing techniques to complete several focused tasks related to the following topics: the mechanisms behind and implications of terrestrial gamma ray flashes; the connections between lightning stroke parameters and lightning flash characteristics (particularly in unusually energetic strokes); and novel measurements of thundercloud charge density, charging rate, and net thunderstorm charge transfer in lightning. These tasks involve joint analysis of broadband low frequency radio measurements and lightning mapping array (LMA) data, a combination of complementary measurements whose value has been demonstrated in recent work by the research team. Intellectual merit: Recent measurements have provided the first glimpse of what processes are behind TGFs, and the current project is designed to determine what is unusual about the lightning flashes that create TGFs and quantify the processes responsible. This will enable realistic modeling of runaway breakdown in thunderstorms and help determine any link to lightning initiation. Little is known about the quantitative connection between lightning stroke current and charge and the details of the lightning flash, especially in unusual or energetic lightning strokes, and this effort will provide this new basic understanding. New measurements of net thunderstorm charge transfer and of charge density in thunderstorms under a wide range of conditions will also provide new bounds on these parameters that are linked to the processes that drive charge separation in thunderstorms. The technical approach applies a powerful technique of joint analysis of broadband radio and LMA measurements. It also builds on existing data or new data with largely existing instrumentation, which ensures the project can be completed as cost-effectively as possible.Broader impacts: The research 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 the research, and internally funded undergraduate research assistants will also be involved. Recent undergraduate involvement has led to a first-author publication for the student and a graduate research assistantship in the lightning field. 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 television interviews. NSF support is critical for maintaining the ability to support this engagement with the public. The measurements are a resource to the broader atmospheric electricity and atmospheric science community and have been used in presentations and publications by many investigators as part of national and international collaborations. The measurements also have significant practical links to lightning hazard detection and could help better identify and mitigate their impact.