Sankha Nanayakkara

Features of K-Changes Observed in Sri Lanka in the Tropics

General characteristics of K-changes, including their duration and probability of occurrence associated with ground flashes in Sri Lanka in the tropics, together with their fine structure, are presented. In 98 ground flashes where the small step changes associated with K-changes are clearly visible, there were about two K-changes per flash on average. The mean K-change time duration observed in this study is 0.38 ms. In 53 of the ground flashes, there were 120 consecutive K-changes. In these cases, the geometric mean of the time interval between K-changes was 12 ms. Analysis of the fine structure of the K-changes reveals the K-changes are always associated with either a chaotic pulse train or a combination of chaotic and regular pulse trains. The results suggest that the small step-like static electric fields identified in the literature as K-changes are the step-like static fields associated with the processes that generate chaotic or a combination of chaotic and regular pulse trains. Thus, at larger distances where the static fields are negligible, K-changes may appear as a chaotic pulse train or a combination of chaotic and regular pulse trains.

Electric field change of M component

Temporary increase of luminosity of lightning channel during the stage of long continuing current is known as the M components. In this study 17 M components of 14 lightning flashes recorded with 10 ns sampling resolution is analyzed. Results suggest that in all analyzed cases the electric field change of M components is embedded with chaotic pulses.

K - change : Is it a static field of a chaotic pulse burst?

Electric field changes associated with K - changes have been studied since 1956. In this study, the electric field variations of K changes observed in the tropics, in Sri Lanka, was analyzed to study the inter K change duration, K change duration, and possible contribution from other activities on K changes. Selected 144 k-changes of 64 lightning flashes, measured with 6.4 ns sampling rate were used for the analysis. The inter K change time interval was found to vary from 0.62 ms to 75.92 ms with an average of 16.92 ms. The duration of K-changes were found to vary from 0.44 ms to 1.65 ms with an average value of 0.48 ms. In this study, it was observed that all K - changes were combined with chaotic pulse trains (CPT). This suggests that the K - changes may be a result of slow electric field changes associated with chaotic pulse activities.