The temporal structure of RF radiation from lightning

Radiation from lightning in the RF band from 3-300 MHz has been examined. Simultaneous measurements were made of the RF radiation from lightning together with records of fast and slow field changes. Continuous analogue recordings were made with a system having 300 kHz of bandwidth in the RF channels. The temporal history of RF radiation of these frequencies consists of a sequence of discrete pulses. The data reveal a distinct pattern in the radiation which is independent of frequency and depends on the type of lightning flash: Cloud-to-ground flashes are characterized by an abrupt beginning associated with the stepped leader, whereas cloud-to-cloud flashes begin with a slower train of noise pulses more typical of the end of both types of flash. An exception to this pattern is cloud-to-ground flashes preceded by a breakdown phase, in which case the radiation begins like a cloud-to-cloud flash.