@Article{SabaLauSchSilMan:2023:UpLeIn,
               author = "Saba, Marcelo Magalh{\~a}es Fares and Lauria, Paola Beatriz and 
                         Schumann, Carina and Silva, Jos{\'e} Cl{\'a}udio de O. and 
                         Mantovani, Felipe de L.",
          affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)} and {Instituto 
                         Nacional de Pesquisas Espaciais (INPE)} and {University of the 
                         Witwatersrand} and APTEMC and {Instituto Nacional de Pesquisas 
                         Espaciais (INPE)}",
                title = "Upward leaders initiated from instrumented lightning rods during 
                         the Approach of a downward leader in a cloud-to-ground flash",
              journal = "Journal of Geophysical Research: Atmospheres",
                 year = "2023",
               volume = "128",
               number = "8",
                pages = "e2022JD038082",
                month = "Apr.",
             keywords = "upward connecting leader, unconnected upward leaders, 
                         cloud-to-ground flash, lightning rod, lightning protection 
                         systems, current measurements.",
             abstract = "In this paper we analyze electric-field and current measurements 
                         of upward leaders induced by a downward negative lightning flash 
                         that struck a residential building. The attachment process was 
                         recorded by two high-speed cameras running at 37,800 and 70,000 
                         images per second and the current measured in two lightning rods. 
                         Differently from previous works, here we show, for the first time, 
                         current measurements of multiple upward leaders that after 
                         initiation propagate to connect the negative downward moving 
                         leader. At the beginning of the propagation of the leaders that 
                         initiate on the instrumented lightning rods, current pulses appear 
                         superimposed to a steadily increasing DC current. The upward 
                         leader current pulses increase with the approach of the downward 
                         leader and are not synchronized but present an alternating 
                         pattern. All 2D leader speeds are approximately constant. The 
                         upward leaders are slower than the downward leader speed. The 
                         average time interval between current pulses in upward leaders is 
                         close to the interstep time interval found by optical or electric 
                         field sensors for negative cloud-to-ground stepped leaders. The 
                         upward leaders respond to different downward propagating branches 
                         and, as the branches alternate in propagation and intensity, so do 
                         the leaders accordingly. Right before the attachment process the 
                         alternating pattern of the leaders ceases, all downward leader 
                         branches intensify, and consequently upward leaders synchronize 
                         and pulse together. The average linear densities for upward 
                         leaders (49 and 82 mu C/m) were obtained for the first time for 
                         natural lightning. Plain Language Summary The effectiveness of a 
                         lightning protection system depends on its efficiency to intercept 
                         the down coming leader of a cloud-to-ground lightning flash. The 
                         interception is usually done by an upward connecting leader that 
                         initiates from grounded structures, humans, or living beings that 
                         protrude from nearby ground. The understanding of the upward 
                         connecting leader and of the attachment process with the downward 
                         leader plays an important role in the determination of the zone of 
                         protection and therefore in the improvement of a lightning 
                         protection system. Unconnected upward leaders, that is, upward 
                         leaders that fail to connect the downward leader, are also of 
                         great importance in lightning protection. They can be large enough 
                         to cause damage to equipment vulnerable to sparks or induced 
                         currents, and enough to injure people from who it initiates. In 
                         this paper we analyze electric-field, speed, and current 
                         measurements of upward leaders induced by a downward negative 
                         lightning flash that struck a residential building. The attachment 
                         process was simultaneously recorded by two high-speed cameras, an 
                         electric-field sensor, and current sensors installed on two 
                         lightning rods. Differently from previous works we show, for the 
                         first time, current measurements of multiple upward leaders 
                         induced by the negative downward moving leader.",
                  doi = "10.1029/2022JD038082",
                  url = "http://dx.doi.org/10.1029/2022JD038082",
                 issn = "2169-8996 and 2169-897X",
             language = "en",
           targetfile = "JGR Atmospheres - 2023 - Saba - Upward Leaders Initiated From 
                         Instrumented Lightning Rods During the Approach of a 
                         Downward.pdf",
        urlaccessdate = "16 jun. 2024"
}