Summary

International Symposium on Electromagnetic Compatibility

2009

Session Number:24S2

Session:

Number:24S2-2

Observations of Bipolar Lightning Flashes Using the VHF Broadband Digital Interferometer

M. Akita,  

pp.785-788

Publication Date:2009/7/20

Online ISSN:2188-5079

DOI:10.34385/proc.14.24S2-2

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Summary:
Lightning Research Group of Osaka University (LRG-OU) has been developing and improving the VHF broadband digital interferometer (DITF) for thunderstorm observations. It enables us to locate the impulsive VHF radiation sources caused by lightning discharges with extremely high resolutions. As a result of the VHF observations during the '07-'08 winter season in the Japan Sea coastal area, lightning flashes that neutralize both positive and negative charges inside thunderclouds. The bipolar lightning flashes are visualized by the VHF broadband DITF. The subsequent negative breakdown in bipolar flashes initiates from the proximity of the initiation point of the precedent negative breakdown some tens millisecond after the first return stroke. It is presumed that the bipolar lightning flashes have reversal of the polarity of neutralized charges. It might be caused by the unusual electrical structure of winter thunder-clouds.