Regular Pulse Trains in Chaotic pulse Bursts

Electric field pulse bursts generated by lightning flashes are considered as sources of high radio frequencies. In this study, an analysis of pulse bursts in electric field records of 30 negative cloud to ground lightning flashes recorded in the southern coastal area of Sri Lanka is presented. Sixty-four percent (64%) of pulse bursts are typical chaotic pulse trains (CPT). Twenty-four percent (24%) of pulse bursts exhibit CPT characteristic while containing regular pulses within the burst. These are termed as “semi-regular pulse bursts” in this study. The regular pulses within CPTs show characteristics similar to dart stepped leaders or stepped leaders, and in some cases, more than one regular pulse trains with different characteristics are observed within a single burst. The intra-cloud lightning activities associated with CPT such as K changes, leader processes, and isolated pulses bursts also exhibit regular pulse bursts or semi-regular pulse bursts. CPT and regular pulse trains always show similarity in occurrence, and semi-regular pulses have the characteristic of both type of pulse bursts. Hence CPT and semi-regular pulse bursts may be formed by superposition of two or more regular pulse bursts which represent dart stepped leader or stepped leader type activities. Keywords-lightning; pulse bursts; chaotic pulses; regular pulses; superimposition;