CAREER: Experimental Research on the Runaway Breakdown of Air During Thunderstorms

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This CAREER project consists of observing x-rays, gamma rays, and energetic electrons from thunderstorms and in laboratory experiments to study the runaway breakdown of air in thunderstorm conditions. Runaway breakdown is a process in which an avalanche of high-energy electrons develops in a strong electric field, producing x-rays, gamma rays, and secondary ionization, and transporting large quantities of charge great distances. This process can occur when the energy gained by an electron accelerating in a strong electric field exceeds the energy lost by collisions. It may play a part in lightning initiation and large-scale charge transport in thunderstorms, as well as in explaining x-ray emissions from storms and transient luminous events (sprites and jets) in the high atmosphere above thunderstorms. The goals of the project are to demonstrate whether runaway breakdown occurs in the atmosphere, to test current models of the mechanism, to understand the importance of runaway breakdown in thunderstorm phenomena, and to make experimental scientific research part of every student's normal curriculum. To achieve the goals, the project includes the following work:1. Design and construction of sensitive detectors for x-ray and gamma ray emissions, as part of a senior physics laboratory course. 2. Observing x-rays, gamma rays, and energetic electrons associated with triggered lightning in collaboration with the Lightning Research Laboratory of the University of Florida, Gainesville.3. Conducting laboratory experiments with accelerating electrons in strong electric fields to investigate runaway avalanche; integrating the work into undergraduate physics labs.The project will provide the first direct evidence of the importance of the runaway electron process in air, contribute to the understanding of thunderstorms, and provide students with opportunities for instrument development and research in atmospheric physics.