Simultaneously measured current, luminosity, and electric field pulses in a rocket-triggered lightning flash

Abstract

[1] Current, luminosity, and electric field pulses in a rocket‐triggered negative lightning flash have been analyzed based on the channel base current, high‐speed video images, and electric field changes at 30 m from the channel. Among the 31 distinct current pulses, there are 4 return strokes, 18 typical M components, 5 large M components with unusual large peak current in a range of kiloamperes, 3 initial continuing current (ICC) pulses, and 1 stroke–M component (RM) event which exhibits both return stroke and M component features. The geometric mean of peak current is 13.5 kA, half peak width is 28.4 ms, and risetime from 10% to 90% peak is 1.1 ms for the 4 return strokes, while the corresponding values are 243 A, 400 ms, and 319 ms, respectively, for the 18 typical M components and 5.1 kA, 76.3 ms, and 34.6 ms, respectively, for the 5 large M components. The electric field and current waveforms of ICC pulses exhibit features similar to those of the M components, indicating the similarity of their mechanisms. Detectable optical luminosity is found just prior to all the pulse events, even return strokes. The M components are superimposed on a slowly varying continuing current, while the directly measured current prior to the return strokeisnotsignificant.ThesimultaneouselectricfieldandcurrentwaveformofRMimplies a superposition of dart leader and M incident wave in the channel, and the possible reason is that two branches with common lower portions coexist simultaneously in the upper part of the discharge channel.