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Upward leaders from instrumented lightning rods competing to connect a downward leader during a lightning attachment process
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  • Marcelo Magalhães Fares Saba,
  • Paola Beatriz Lauria,
  • Carina Schumann,
  • José Cláudio Oliveira Silva,
  • Felipe de Lima Mantovani
Marcelo Magalhães Fares Saba
INPE - National Institute for Space Research

Corresponding Author:[email protected]

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Paola Beatriz Lauria
INPE - National Institute for Space Research
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Carina Schumann
The Johannesburg Lightning Research Laboratory
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José Cláudio Oliveira Silva
APTEMC
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Felipe de Lima Mantovani
INPE - National Institute for Space Research
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Abstract

In this paper we analyze electric-field and current measurements of competing 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, the behavior of multiple upward leaders that after initiation compete 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 leader speeds are 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 µC/m) were obtained for the first time for natural lightning.