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@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 = "23 nov. 2020"
}


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