Campos L. Z. S., M. M. F. Saba, M. G. Ballarotti, O. Pinto Jr., W. Schulz:
Characteristics of preliminary Breakdown for first Strokes and subsequent New-Channel Strokes
International Conference on Grounding and Earthing and 2
nd International Conference on Lightning Physics and Effects (GROUND/LPE), Maceió, Brazil, 2006
The aim of this work is to obtain some characteristics of the preliminary breakdown (PB) pulses for negative cloud-to-ground flashes. We present the correlation between the electric field peak of first strokes and subsequent new-channel strokes and the time interval from the beginning of the PB and the stroke event. For this purpose we employed a high-speed observation system (with a time resolution of 1000 frames per second), electric field measurements (flat plate antenna) and data from the Brazilian Lightning Location System - RINDAT. All the measurement systems were synchronized with GPS. All measurements and observations were made in S. José dos Campos (45.864°W; 23.215°S), Brazil. The beginning of the PB pulses could be determined both in the electric field data and in the high-speed video recordings (in which it is possible to observe a low intensity light emission from the cloud). The identification of this instant is a very difficult task in the absence of the images. The electric field peak values of the strokes were all normalized to 100 km, based on the location solution given by RINDAT. An amount of 30 first strokes and 16 subsequent new-channel strokes, all from the same day (March 23rd, 2005), were analyzed, and
their data (PB to stroke time interval versus the inverse of the stroke electric field peak) were plotted. The graph obtained for first strokes showed a linear relationship (correlation coefficient: 0.85). No correlation was found for subsequent new-channel strokes.
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