Acoustic properties of triggered lightning

Monday, 15 December 2014
Maher A Dayeh1, Neal Evans1, James Ramaekers1, John Trevino1, Hamid Rassoul2, Robert J Lucia2, Joseph R Dwyer3,4, Martin A Uman5 and Douglas M Jordan6, (1)Southwest Research Institute, San Antonio, TX, United States, (2)Florida Inst of Technology, Melbourne, FL, United States, (3)University of New Hampshire Main Campus, Institute for the Study of Earth, Oceans, and Space, Durham, NH, United States, (4)University of New Hampshire Main Campus, Department of Physics, Durham, NH, United States, (5)Univ Florida, Gainesville, FL, United States, (6)Univ of Florida, Starke, FL, United States
Acoustic signatures from rocket-triggered lightning are measured by a 15m long, one-dimensional microphone array consisting of 16 receivers situated 90 meters from the lightning channel. Measurements were taken at the International Center for Lightning Research and Testing (ICLRT) in Camp Blanding, FL during the summer of 2014. The linear array was oriented in an end-fire position so that the peak acoustic reception pattern can be steered vertically along the channel with a frequency-dependent spatial resolution, enabling us to sample the acoustic signatures from different portions along the lightning channel. We report on the characteristics of acoustic signatures associated with several return strokes in 6 measured flashes (total of 29 return strokes). In addition, we study the relationship between the amplitude, peak frequency, and inferred energy input of each stroke acoustic signature and the associated measured lightning parameters. Furthermore, challenges of obtaining acoustic measurements in thunderstorm harsh conditions and their countermeasures will also be discussed.