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Abstract

Based on the analysis of the average characteristics of the radio emission of a thundercloud, namely, the rms value (intensity) and the kurtosis coefficient, calculated over short time intervals (100 microseconds), specific events were detected, probably corresponding to cloud-to-ground lightning discharges. These events begin suddenly with a series of fairly rare submicrosecond bipolar pulses of large amplitude, which manifests itself in a moderate intensity level and high values of the kurtosis coefficient. This stage of the event can last from a few to several hundred milliseconds and can be called the preparatory stage of a lightning discharge. The next stage is characterized by a successive decrease in the kurtosis coefficient with a slight change in both the amplitude and intensity of the radiation, and a decrease in the level of intensity fluctuations and the kurtosis coefficient, which indicates an increase in the frequency and a decrease in the amplitude of the pulses, as well as the possible appearance of a noticeable quasi-continuous (noise) component in the lightning radiation clouds. This stage may be associated with the development of a stepped lightning leader. Finally, the event ends with a sharp peak in intensity and a drop in the kurtosis coefficient to the background level, which corresponds to a return lightning strike. Observation of the short-wavelength radio emission of a thundercloud can make it possible to predict the time of a lightning strike (in a few tens of milliseconds), and, in combination with interferometry, its location.