Physical Properties of Radiation Fields Produced by Multiple In-cloud Lightning Discharges

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This paper describes some physical properties and statistical analyses of radiation fields associated with multiple in-cloud lightning discharges. A wide-band waveform recording system was employed to analyze the time-domain characteristics of the radiation fields. The radiation fields produced by in-cloud lightning discharges were significantly different from cloud-to-ground return stroke fields and showed pronounced bipolar pulse peak amplitudes comparable to those of cloud-to-ground return stroke fields. The time intervals between the subsequent strokes for both the positive and negative radiation fields decrease as the stroke order increases. The ratio of the peak of the subsequent strokes to the first stroke peak is distributed over a wide range. Little difference was observed compared with the results for both the positive and negative polarities. The time intervals between the superimposing narrow stepwise pulses in the initial half-cycle of the pronounced bipolar pulse were in the range of less than 12 $\mu$s and the mean values for the positive and negative polarities were 4.43 $\mu$s and 4.78 $\mu$s, respectively. The statistics on the parameters of the electric and magnetic field waveforms seem to provide a good quantitative estimate of the lightning protection device response to the electromagnetic pulse effects of in-cloud lightning discharges.
2001-01-15