Electromagnetic radiation from lightning strokes

Abstract A theory is given of the spectral distribution and the absolute amount of low frequency electromagnetic radiation emitted from a vertical lightning stroke from cloud to ground. The calculation depends on an assumed physical mechanism for the flow of charge on the discharge channel, but the model corresponds closely to the empirical observations of Schonland, Pierce, and others. The radiated energy has a maximum intensity at about 11 kc/sec and a total width at half-maximum of 12 kc/sec. The predicted radiation in the megacycle region agrees reasonably well with that reported by Chandrashekhar Aiya, although the present theory was developed primarily for the low frequency region.The total energy radiated in one leader and return stroke is estimated to be about 220,000 joules.