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Three‐dimensional imaging of upward positive leaders in triggered lightning using VHF broadband digital interferometers
Author(s) -
Yoshida S.,
Biagi C. J.,
Rakov V. A.,
Hill J. D.,
Stapleton M. V.,
Jordan D. M.,
Uman M. A.,
Morimoto T.,
Ushio T.,
Kawasaki Z.I.
Publication year - 2010
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2009gl042065
Subject(s) - thunderstorm , lightning (connector) , broadband , astronomical interferometer , current (fluid) , physics , geology , channel (broadcasting) , very high frequency , meteorology , optics , geodesy , remote sensing , telecommunications , electrical engineering , interferometry , computer science , engineering , power (physics) , quantum mechanics , thermodynamics
Upward positive leaders (UPLs) in two artificially‐initiated lightning flashes were imaged in three dimensions using VHF broadband digital interferometers and a high‐speed video camera with time‐synchronized channel‐base current measurements. Locatable VHF sources of the two UPLs began at 1.1 km and 1.5 km, a few milliseconds after the UPL inception, and ascended to 2.4 km and 3.7 km, respectively, with average 3‐D speeds on the order of 10 6 ms −1 . The initial stage currents for both flashes were unusually large and had peak values of 6 kA and 18 kA. VHF sources associated with positive leader propagation were located when the average current was higher than 3 kA and had significant pulse activity. The source altitudes and channel‐base currents suggest that there might have been a region of significant negative charge at altitudes from 2 to 4 km, which is below the freezing level of typical thunderstorms in Florida.