Reconstructing the 3D shape of lightning strikes from their thunder
A nearby lightning strike is accompanied by a loud roll of thunder that can last for many seconds. The stroke conducts current between cloud and ground, simultaneously superheating the air along the path of the stroke. The resultant shock wave expands outwards and forms the sound of thunder all along the length of the stroke, reaching the listener at the much slower speed of sound.
We propose to reconstruct the lightning stroke path using the sound of thunder recorded at three or more locations separated by 1 km or more. The audio data is acquired by recording two audio channels with a computer. One channel is fed by a microphone placed outside (but not to be a lightning strike risk!) and the other channel is fed by an FM radio. The lightning strike causes a burst of radio waves that is picked up by the radio and serves as a time tag for synchronisation. Suggested reconstruction is by drawing hemispherical shells around each location with radius from speed of sound times time from strike and intensity by the amplitude of the thunder, colouring them red, green and blue, and then the path of the lightning strike will appear as a white line.
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Nice idea. Presumably the reconstruction process could draw from current electromagnetic detection systems (Nag 2015 DOI:10.1002/2014EA000051). What do you think measuring the sound waves could offer which is not already possible by measuring the VHF electromagnetic emission?
Declan Finney · 16 May, 2016