Lightning Initiation and In-Cloud Electromagnetic Activity in Mississippi Thunderstorms

虽然关于闪电我们已经知道了很多，但我们仍然不知道闪电是如何产生的。不知何故，引爆过程将不导电的空气转变成一个短细的导体或初始闪电通道；然后闪光的其余部分就从这个初始通道发展出来。研究人员尚未完全了解闪电最初产生火花的物理机制，以及这些火花如何将不导电的空气转化为高导电性的闪电通道。这项研究将分析几个月的闪电数据，以获得对引爆过程的新理解。该项目结合了一套不同寻常的传统和最先进的研究传感器，以促进对闪电引发的理解。这项研究通过潜在地改善对闪电启动的理解和改进的闪电警报系统，具有强大的社会影响。这项研究试图分析2016年夏季在密西西比州北部收集的闪电数据，以研究导致闪电引发的云层放电事件。这些事件包括快速正向击穿、窄双极事件(NBE)、初始电场变化(IECS)和初始击穿脉冲(IBPs)。这项新研究的新颖性和潜在的变革性方面在于新数据，其中包括来自电场导数传感器和甚高频(VHF)传感器的测量。VHF传感器特别适合于研究闪电引发的事件，因为尽管人们对空气中的电放电了解不多，但已知的是，空气中的电放电会产生HF和VHF辐射。分析将考虑最近发现的快速正向击穿，并将调查正向击穿与后续事件的联系有多快。将进行类似的研究，以研究甚高频脉冲如何影响IECS或IBP。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Although much is already known about lightning flashes, we still do not understand how a flash initiates. Somehow the initiation processes turn the non-conducting air into a short, thin conductor or initial lightning channel; the rest of the flash then develops from this initial channel. Researchers do not yet fully understand exactly what physical mechanisms cause the first sparks of a lightning flash and how those sparks transform the non-conducting air into the highly conductive lightning channel. This study will analyze several months of lightning data to gain new understanding of initiation processes. This project combines an unusual suite of traditional and state-of-the-art research sensors to advance the understanding of lightning initiation. This research has strong societal impact through potentially improved understanding of lighting initiation and improved lightning warning systems. This research seeks to analyze lightning data collected in northern Mississippi during summer 2016 to study cloud discharge events that lead to lightning initiation. Those events include fast positive breakdown, narrow bipolar events (NBEs), initial electric field changes (IECs), and initial breakdown pulses (IBPs). The novelty, and potentially transformative aspect of this new research, is in the new data, which includes measurements from an electric field derivative sensor and a very high frequency (VHF) sensor. The VHF sensor is particularly suitable for studying the lightning initiating events, because although not well understood, electrical discharges in air are known to produce HF and VHF radiation.  The analysis will take into consideration the recent discovery of fast positive breakdown and will investigate how fast positive breakdown is connected to the events that follow. A similar line of research will be conducted to study how VHF pulses affect IECs or IBPs.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.