Lightning Initiation and In-Cloud Electromagnetic Activity in Mississippi Thunderstorms

点击翻译按钮获取中文摘要

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.