Publication Date:
2015-01-09
Description:
Using high-speed cameras, Lightning Attachment Process Observation Systems (LAPOSs) and fast and slow electrical antennae, we documented a downward bipolar lightning flash that contained one first positive stroke with a peak current of 142 kA and five subsequent negative strokes hitting on a 90 m tall structure on 2010-7-29 in Guangzhou City, China. All the six strokes propagated along the same viewed channel established by the first positive return stroke. The leader which preceded the positive return stroke propagated downward without any branches at a two-dimensional (2D) speed of 2.5 × 10 6 m/s. An upward connecting leader with a length of about 80 m was observed in response to the downward positive leader. The 10-90% rise times of the return strokes’ optical pulses ranged from 2.2 µs to 3.2 µs, while the widths from the 10% wave front to the 50% wave tail ranged from 56.5 µs to 83.1 µs, and the half peak widths ranged from 53.4 µs to 81.6 µs. All the return strokes exhibited similar speeds, ranging from 1.0 × 10 8 m/s to 1.3 × 10 8 m/s. Each of the return strokes was followed by a continuing current stage (CC). The first positive stroke CC lasted more than 150 ms, much larger than all the subsequent negative stroke CC, ranging from 13 ms to 70 ms.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
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