On the VLF/LF radiation pulse shapes at the initial milliseconds of lightning discharges

This report examines the shape and amplitude of the VLF/LF radiation pulses within the initial milliseconds of lightning discharges. A simple model regarding the discharge process and channel condition is proposed to compute the radiation pulses. With some reasonable assumptions regarding the current propagation speed and the current damp length, the modeled pulses are in good agreement with the observations. Based on our analysis, we infer that lightning channel becomes increasingly active during the first hundreds of mus and then becomes continuously less active thereafter