Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8139017 | Journal of Atmospheric and Solar-Terrestrial Physics | 2018 | 6 Pages |
Abstract
Simultaneously captured vertical and horizontal (total) electric field signatures of lightning negative Return Strokes (RS) were analyzed to obtain Time-Frequency (TF) variation using Stockwell Transformation (ST). In the study, ST was utilized since it is known to possess comparatively better time resolution at high frequency regions compared to other available TF methods. The data were obtained during the monsoon season of April-May 2014. The vertical and horizontal component of fifty negative RSs was utilized in the study. The resultant ST spectrum was analyzed and the regions of interest were demarcated based on the color which represented their relative power output intensities for different frequency components of the signal. The spread area was identified as the region of frequencies which consisted of power intensity equal or above 90th percentile when compared to the maximum possible value. The spectral area was identified as the area of frequencies in the borderline to the natural background noise. The spread region for the vertical E field had a range between 10â¯kHz and 650â¯kHz. Its average values were in between 126â¯kHz and 331â¯kHz. The spectral region of the vertical electric field change spanned from 1â¯kHz to 1020â¯kHz. Its average distribution was 44â¯kHz-660â¯kHz. Horizontal electric fields had a range of 20â¯kHz-1940â¯kHz in the spectral region. The same for the spread region was 80â¯kHz-910â¯kHz. The averages of the horizontal E field's spectral region were 46-1112â¯kHz and its spread region varied between 227 and 599â¯kHz. The results display a higher frequency range for all aspects of the horizontal E field changes which implies that its influence on the high frequency radiation is much higher than its vertical counterpart.
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Authors
T.A.L.N. Gunasekara, S.N. Jayalal, M. Fernando, U. Sonnadara, V. Cooray,