Collaborative Research: Observations of Gamma Emissions and Electric-Field Changes in and above Thunderstorms during STEPS

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The Severe Thunderstorm Electrification and Precipitation Study field program (STEPS), planned for the early summer of 2000 in western Kansas, will provide a wide range of observations in and around thunderstorms using aircraft, radar, and other observing systems. As part of STEPS, Dr. Eack and his Co-PI Dr. William Beasley of the University of Oklahoma will launch balloons that are equipped with special instruments to measure gamma rays (and x-rays) and short-term fluctuations in the electric field at altitudes within and just above thunderstorms. They will also arrange for a gamma-ray detector to be flown on the South Dakota T-28 armored aircraft. Objectives of the research are (1) to test hypotheses for the production of transient luminous events (TLEs) including sprites, elves, and blue jets, which are observed at altitudes in the middle atmosphere above thunderstorms; (2) to test hypotheses for the production of bremsstrahlung radiation within thunderstorms by runaway electron processes; (3) to evaluate models for lightning initiation and return strokes. Data analysis will be closely coordinated with other NSF-supported STEPS projects, including the New Mexico Tech lightning mapper (ATM-9912073), the CHILL radar (ATM-9912051 and -9982030), the South Dakota armored aircraft (ATM-9981175), balloon soundings of the electrical field (ATM-9912562), and visual observations of TLEs (ATM-0000569).