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Bipolar cloud‐to‐ground lightning flash observations
Author(s) -
Saba Marcelo M. F.,
Schumann Carina,
Warner Tom A.,
Helsdon John H.,
Schulz Wolfgang,
Orville Richard E.
Publication year - 2013
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/jgrd.50804
Subject(s) - lightning (connector) , flash (photography) , peak current , polarity (international relations) , physics , meteorology , channel (broadcasting) , geodesy , geology , optics , computer science , telecommunications , power (physics) , genetics , electrode , quantum mechanics , biology , electrochemistry , cell
Abstract Bipolar lightning is usually defined as a lightning flash where the current waveform exhibits a polarity reversal. There are very few reported cases of cloud‐to‐ground (CG) bipolar flashes using only one channel in the literature. Reports on this type of bipolar flashes are not common due to the fact that in order to confirm that currents of both polarities follow the same channel to the ground, one necessarily needs video records. This study presents five clear observations of single‐channel bipolar CG flashes. High‐speed video and electric field measurement observations are used and analyzed. Based on the video images obtained and based on previous observations of positive CG flashes with high‐speed cameras, we suggest that positive leader branches which do not participate in the initial return stroke of a positive cloud‐to‐ground flash later generate recoil leaders whose negative ends, upon reaching the branch point, traverse the return stroke channel path to the ground resulting in a subsequent return stroke of opposite polarity.