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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

High-speed video and electromagnetic analysis of two natural bipolar cloud-to-ground lightning flashes

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Saraiva, A. C. V. [1] ; Campos, L. Z. S. [1] ; Williams, E. R. [2] ; Zepka, G. S. [1] ; Alves, J. [1] ; Pinto, Jr., O. [1] ; Heckman, S. [3] ; Buzato, T. S. [1] ; Bailey, J. C. [4] ; Morales, C. A. [5] ; Blakeslee, R. J. [6]
Total Authors: 11
[1] Natl Inst Space Res, Sao Jose Dos Campos - Brazil
[2] MIT, Dept Civil & Environm Engn, Cambridge, MA 02139 - USA
[3] Earth Networks, Germantown, MD - USA
[4] Univ Alabama, Earth Syst Sci Ctr, Huntsville, AL 35899 - USA
[5] Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, Sao Paulo - Brazil
[6] NASA Marshall Space Flight Ctr, Huntsville, AL - USA
Total Affiliations: 6
Document type: Journal article
Source: JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES; v. 119, n. 10, p. 6105-6127, MAY 27 2014.
Web of Science Citations: 16

High-speed video records of two bipolar cloud-to-ground flashes were analyzed in detail. They both began with a single positive return stroke that was followed by more than one subsequent weak negative stroke. Due to the elevated cloud base height of its parent thunderstorm, the preparatory processes of each subsequent negative stroke were documented optically below cloud base. In the first event (Case 1) it was observed that all four subsequent negative strokes were initiated by recoil leaders that retraced one horizontal channel segment previously ionized by the positive leader. Those recoil leaders connected to the original vertical channel segment and propagated toward ground, producing four subsequent strokes that had the same ground contact point as the original positive discharge. The second event (Case 2), in contrast, presented 15 subsequent strokes that were initiated by recoil leaders that did not reach the original channel of the positive stroke. They diverged vertically toward ground, making contact approximately 11 km away from the original positive strike point. These results constitute the first optical evidence that both single-and multiple-channel bipolar flashes occur as a consequence of recoil leader activity in the branches of the initial positive return stroke. For both events their total channel length increased continuously at a rate of the order of 10(4) m s(-1), comparable to speeds reported for typical positive leaders. (AU)

FAPESP's process: 08/56711-4 - Detection of trends in the lightning activity in Brazil related to climatic changes
Grantee:Osmar Pinto Junior
Support type: Research Projects - Thematic Grants
FAPESP's process: 10/01742-2 - High-speed camera network for monitoring and study lightning (RAMMER Project)
Grantee:Antonio Carlos Varela Saraiva
Support type: Scholarships in Brazil - Post-Doctorate
FAPESP's process: 09/15235-8 - Cloud processes of the main precipitation systems in Brazil: a contribution to cloud resolving modeling and to the GPM (Global Precipitation Measurement)
Grantee:Luiz Augusto Toledo Machado
Support type: Research Projects - Thematic Grants