Experimental investigation on correlation between fast-front lightning current and the resultant arc channel luminosity

Abstract

Temporal variation of the luminosity of lightning channel can provide a proxy for the temporal variation of current flowing through it. In this study, seven groups of lightning currents with fast-front waveforms, spanning a 10–90% risetime range from 2.1 to 9.5 μs, a half-peak width range from 35.5 to 147.8 μs, and an amplitude range from 3 to 30 kA, are injected into a 15-mm air gap between a pair of graphite rod electrodes. An analysis is given of waveform associations and of waveform parameter correlations between current pulses and luminosity pulses emitted by the current-carrying channel. The luminosity signature is found to be generally divided into three stages: initial rising stage, initial fast decay stage, and later slow decay stage. During the later slow decay stage, the luminosity follows faithfully with the current (i.e., linearly correlated with current), whereas no such a feature is found in the previous two stages. The current peak is roughly, linearly correlated with the luminosity peak. A roughly linear relationship is found between the current risetime and the luminosity risetime, but no direct correlations are observed between their half-peak widths. In regard of optical signature, it is concluded that the laboratory-generated lightning currents, which are featured with relatively short front times and relatively slow decay after peak, are of similar nature as the return-stroke current in naturally-occurred lightning arc.