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Ann. Geophys., 25, 1509-1517, 2007
www.ann-geophys.net/25/1509/2007/
© European Geosciences Union 2007
Lightning stroke distance estimation from single station observation and validation with WWLLN data
V. Ramachandran, J. N. Prakash, A. Deo, and S. Kumar
School of Engineering and Physics, University of the South Pacific, Suva, Fiji
Abstract. A simple technique to estimate the distance of the lightning strikes d with a
single VLF electromagnetic wave receiver at a single station is described.
The technique is based on the recording of oscillatory waveforms of the
electric fields of sferics. Even though the process of estimating d using the
waveform is a rather classical one, a novel and simple procedure for finding
d is proposed in this paper. The procedure adopted provides two independent
estimates of the distance of the stroke. The accuracy of measurements has
been improved by employing high speed (333 ns sampling rate) signal
processing techniques. GPS time is used as the reference time, which enables
us to compare the calculated distances of the lightning strikes, by both
methods, with those calculated from the data obtained by the World-Wide
Lightning Location Network (WWLLN), which uses a multi-station technique. The
estimated distances of the lightning strikes (77), whose times correlated,
ranged from ~3000–16 250 km. When d<3500 km, the average
deviation in d compared with those calculated with the multi-station
lightning location system is ~4.7%, while for all the strokes it
was ~8.8%. One of the lightnings which was recorded by WWLLN,
whose field pattern was recorded and the spectrogram of the sferic was also
recorded at the site, is analyzed in detail. The deviations in d calculated
from the field pattern and from the arrival time of the sferic were 3.2%
and 1.5%, respectively, compared to d calculated from the WWLLN location. FFT
analysis of the waveform showed that only a narrow band of frequencies is
received at the site, which is confirmed by the intensity of the
corresponding sferic in the spectrogram.
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