Abstract:
- Isolated Narrow Bipolar Pulses (NBP) have been
observed in the past in sub tropical and tropical regions. This study
presents detail electric field characteristics of NBP pulses observed
in Sri Lanka in the tropic. NBP analyzed in this work were
recorded at Matara (5.95 N, 8.53 E), southern coast of Sri Lanka
from four highly active thunderstorm days in May 2013. The
waveforms were recorded with a 10 ns resolution within a 100 ms
time window. In contrary to previous observations at the same
geographical region, both positive and negative NBP pulses were
observed in this study. Parameters related to Narrow Negative
Bipolar Pulses (NNBP) are presented in this study since majority of
the observations were in that category. The parameters measured
for NNBP's were rise time (Tr), zero crossing time (Tz), the
duration of slow front (Ts), the full width at half maximum
(FWHM) and the ratio of amplitude of overshoot to the
corresponding peak amplitude (Os/Pa). The corresponding average
values for these parameters were found to be 0.49 µs, 2.83 µs, 0.18
µs, 1.18 µs and 0.17 respectively. The above values conforms to a
much narrower bipolar pulses when compared to values reported in
earlier studies.
