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

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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.