@InProceedings{CamposCummPint:2015:ReThSe,
author = "Campos, L. and Cummins, K. and Pinto Junior, Osmar",
affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)} and {University
of Arizona} and {Instituto Nacional de Pesquisas Espaciais
(INPE)}",
title = "On the relationship between the separation of ground contacts
within a cloud-to-ground flash and their cloud charge sources",
year = "2015",
organization = "IUGG General Assembly, 26.",
abstract = "The processes and mechanisms that lead to the formation of new
ground contacts (NGCs) in negative multiple ground contact flashes
(MGCFs) are investigated through case studies. This was achieved
through the analysis of a dataset collected by a network of eight
slow electric field antennas, high- and standard-speed video
cameras and ten Lightning Mapping Array (LMA) stations installed
in Kansas, USA from May to August 2013. Nine natural MGCFs were
analyzed in detail and the in-cloud processes that led to their
NGC strokes seemed to be intrinsically related to the horizontal
distance between the different ground contact points.
Widely-spaced NGCs (separated by over one kilometer) were formed
from in-cloud branches that were initiated away from the preceding
channels to ground, although the LMA plots clearly showed a common
root. This is consistent with the existence of multiple
closely-spaced regions of high (and lower) negative charge density
within a cloud, or with horizontal variations in the lower
positive charge region that can facilitate or inhibit preliminary
breakdown in specific areas. Closely-spaced NGCs (separated by
hundreds of meters), on the other hand, were formed when a
subsequent dart leader diverged from the original path of a
preceding stroke as it was already moving towards ground, a
process that can be also be seen in the video records. In both
types of NGC formation, a fast field recovery was observed in
close (up to 5 km) electric field measurements following the
stroke that preceded the NGC, suggesting that charge with the same
polarity as the return stroke was accumulating in the channel and
not flowing to ground. For contrast, ten case studies of
multi-stroke, single ground contact flashes were analyzed and none
of them presented this signature.",
conference-location = "Prague, Czech Republic",
conference-year = "22 June - 02 July",
urlaccessdate = "29 mar. 2024"
}