Collaborative Research: High-Speed Slitless Spectroscopy Studies of Natural Lightning Flashes

闪电每年导致许多人死亡，并损坏企业和家庭的电网和电子设备。闪电最大的谜团之一是闪电是如何启动的。我们知道，引发过程将不导电的空气转变为一种称为闪电通道的短细导体，但目前尚不清楚是什么物理机制引发了闪电的第一批火花，也不知道这些火花何时产生导电通道。该项目将使用三个高速摄像机和七个电场变化传感器收集有关闪电引发的新数据。这项研究的主要社会影响将是提高我们对闪电引发的知识，并通过这项研究产生的改进的闪电预警系统潜在地拯救生命。数据收集将集中在形成闪电通道所需的时间内发生的初始火花(持续时间仅为百万分之五到万分之五秒)，大约是闪电的前千分之三到万分之一秒。摄像机将使用100,000到300,000帧/秒的帧速率记录下初始脉冲的发展过程，这比以前用于研究闪电引发的帧速率更高。为了确定初始脉冲通道是否足够热以成为良好的导体(即阶跃先导)，将使用在20微秒或更高分辨率下获得的光谱来测量初始阶段和返回冲程期间作为时间函数的温度发展。具有高达5微秒分辨率和更高灵敏度的数据还将用于研究研究小组早期工作中似乎看到的更复杂的行为，并比较云对地(CG)和互云(IC)闪存启动。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。

Lightning flashes kill many people each year and damage power grids and electronic equipment in businesses and homes. One of the greatest mysteries about lightning is how a flash initiates. We know that the initiation processes turn non-conducting air into a short, thin conductor called the lightning channel, but it is not known exactly what physical mechanisms cause the first sparks of a lightning flash nor when these sparks produce the conducting channel. This project will collect new data on lightning initiation using three high-speed video cameras and seven electric field change sensors. The main societal impact of this research will be to improve our knowledge of lightning initiation and, potentially, save lives through improved lightning warning systems resulting from this research. The data collection will focus on the initial sparks (with durations of only 5 to 60 millionths of a second) that occur during the time needed to form the lightning channel, roughly the first 3 to 10 thousandths of a second of a lightning flash. The video cameras will record the development the initial pulses using frame rates of 100,000 to 300,000 frames/second, higher than previously used to study lightning initiation. To determine whether the initial pulse channel is hot enough to be a good conductor (i.e. stepped leader) spectra acquired at 20 micro-seconds resolution or better will be used to measure the temperature development as a function of time during the initial stage and during the return stroke. Data with up to 5 micro-second resolution and better sensitivity will also be used to study the more complicated behavior that seems to have been seen in the research group's earlier work and to compare cloud-to-ground (CG) and intercloud (IC) flash initiation.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.