TY - CONF
T1 - Phenomenology and characterization of multiple ground contact strokes in natural lightning
AU - Campos, Leandro Z.S.
AU - Saraiva, Antonio C.V.
AU - Cummins, Kenneth L.
AU - Antunes, Larissa
AU - Junior, Osmar Pinto
AU - Guedes, Dailton G.
N1 - Funding Information:
The authors would like to thanks Vanguarda TV channel, Simoldes Plásticos and Instituto de Estudos Avançados (IEAv) for their support during the 2012/2013 observation campaign. This work has been supported by FAPESP (Fundação de Amparo à Pesquisa do Estado do São Paulo) under grant numbers 08/56711-4 and 2010/01742-2 and the scholarship 2013/18785-4.
Publisher Copyright:
© International Conference on Atmospheric Electricity, ICAE 2014
PY - 2014
Y1 - 2014
N2 - An analysis of the phenomenology and overall characteristics of 35 cloud-to-ground (CG) strokes that create two or more contact points to the ground in a millisecond scale are presented. This dataset includes both the “classical” forked strokes (first observed in streak camera records) and the new class of this type of phenomenon, called “upward illumination” strokes, introduced in more recent works. The broad class of strokes that present two or more contact points in a millisecond and sub-millisecond scale was termed “multi ground contact strokes” (MGCS) as their geneses are very similar: one branch from the main trunk of a stepped leader produces a second stroke shortly after the first return stroke occurs. Over a five-day campaign, a total of 357 negative CG flashes were recorded by the RAMMER network, which is comprised of four high-speed video cameras (three stationary monochromatic and one mobile colored). They were set up for recording with 1200 x 500 pixels per frame, at 2500 frames per second (390-µs exposure time). From careful visual inspection, 35 MGCS events were found, among which 22 were classified as forked strokes and 13 as UI strokes. RAW data from BrasilDAT network was used to identify and give additional information about the MGCS. After a number of detailed case studies and a review of the recent literature, it was found that the main difference between UI and classical forked stroke events are: a) UI stroke channels present an optical discontinuity from the main trunk during its development (i.e., there was a region of lower or no apparent luminosity between its brighter region and the forking point from the main channel), b) the time between strokes is longer than in the case of classical forked strokes and c) the peak currents of the UI strokes are, usually, very small. Analysis of the relationship between the interstroke interval and peak current added new information on the physical characteristics and distinctive features of UI and forked strokes.
AB - An analysis of the phenomenology and overall characteristics of 35 cloud-to-ground (CG) strokes that create two or more contact points to the ground in a millisecond scale are presented. This dataset includes both the “classical” forked strokes (first observed in streak camera records) and the new class of this type of phenomenon, called “upward illumination” strokes, introduced in more recent works. The broad class of strokes that present two or more contact points in a millisecond and sub-millisecond scale was termed “multi ground contact strokes” (MGCS) as their geneses are very similar: one branch from the main trunk of a stepped leader produces a second stroke shortly after the first return stroke occurs. Over a five-day campaign, a total of 357 negative CG flashes were recorded by the RAMMER network, which is comprised of four high-speed video cameras (three stationary monochromatic and one mobile colored). They were set up for recording with 1200 x 500 pixels per frame, at 2500 frames per second (390-µs exposure time). From careful visual inspection, 35 MGCS events were found, among which 22 were classified as forked strokes and 13 as UI strokes. RAW data from BrasilDAT network was used to identify and give additional information about the MGCS. After a number of detailed case studies and a review of the recent literature, it was found that the main difference between UI and classical forked stroke events are: a) UI stroke channels present an optical discontinuity from the main trunk during its development (i.e., there was a region of lower or no apparent luminosity between its brighter region and the forking point from the main channel), b) the time between strokes is longer than in the case of classical forked strokes and c) the peak currents of the UI strokes are, usually, very small. Analysis of the relationship between the interstroke interval and peak current added new information on the physical characteristics and distinctive features of UI and forked strokes.
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M3 - Paper
AN - SCOPUS:85086813454
T2 - 15th International Conference on Atmospheric Electricity, ICAE 2014
Y2 - 15 June 2014 through 20 June 2014
ER -