Further Studies of the Phenomenology and Physics of the Lightning Discharge

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These investigators will study a number of topics related to the lightning discharge, primarily using a facility they have developed in which a wire trailed from a rocket causes lightning to strike their observing facility. They will study such features of lightning as the attachment process (the initial process that determines where lightning will strike) and upward unconnected discharges that are often produced when lightning strikes a nearby location. These latter discharges are thought to be responsible for many fires and other damage in the vicinity of lightning strikes, as well as injury to humans. The investigators will measure the currents in a grounded structure that are produced when lightning strikes nearby and will use imaging cameras to study the discharge process at their instrumented site. They also will use rocket-triggered lightning to measure nitric oxide (NO) production by lightning. NO is a trace gas that affects many important chemical processes in the atmosphere, including ozone production. Previous estimates of the global importance of NO production by lightning have varied substantially, from a minor to a major source, so the investigators hope to use direct measurements in the lightning channel to reduce this uncertainty. A recent additional discovery at their observing facility has been the production of X-rays and other energetic radiation produced by a rocket-triggered lightning. They will continue studies of the nature of this radiation, which promises to provide new information on the energetics of lightning and on the breakdown process. They also plan an evaluation of the ability of the National Lightning Detection Network to detect and locate lightning, because some of their earlier studies have suggested that there are discrepancies in detection efficiency and location that now can be studied accurately using new GPS timing at their site.The work will involve extensive collaboration with international scientists and an active program of graduate education. The investigators will continue to host events for high school science, make their research available through a distance-learning program, incorporate their research results into a course on lightning, and maintain a very active program of outreach activities that makes information about lightning available to the general public. Some aspects of their expected results, especially those associated with upward unconnected discharges, have important connections to public safety. The facility that they have developed will continue to serve as an important focal point for the community and will contribute to the research of many investigators throughout the country and the world.