Open AccessReview and Case Study of Sounds Associated with the Lightning Electromagnetic Pulse
Author(s) -
Timothy A. Coleman,
Kevin R. Knupp,
John T. Tarvin
Publication year - 2009
Publication title -
monthly weather review
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.862
H-Index - 179
eISSN - 1520-0493
pISSN - 0027-0644
DOI - 10.1175/2009mwr2931.1
Subject(s) - thunder , lightning (connector) , electromagnetic pulse , acoustics , pulse (music) , meteoroid , spectrogram , physics , meteorology , computer science , optics , speech recognition , astronomy , power (physics) , quantum mechanics , detector
The electromagnetic pulses (EMPs) associated with two lightning flashes on 22 July 2008 in central Alabama produced audible clicking sounds. These clicks were observed almost simultaneously with the lightning flashes, but a significant period of time before the thunder. The lightning flashes and associated sounds were recorded in digital video and audio by a video camera. Based on theories primarily developed to explain reports of sounds associated with aurora and meteors entering the earth’s atmosphere, it appears that the sounds were associated with transduction of the electromagnetic energy at audible frequencies into vibrations in objects near the camera. Coronal discharges are also possible. Examination of spectrograms of the clicks and the subsequent thunder, and comparison to measurements of the normalized light intensity in each frame of video, show that the clicks must have been associated with sounds in nearby objects. Therefore, the sounds were associated with the lightning EMP.