Abstract
The characteristics of 77 electric field changes of positive cloud to ground (CG) flashes in the tropics of Indonesia were investigated. It was found that the arithmetic mean (AM) and geometric mean (GM) values for 0%–100% and 10%–90% rise time were 12.7 μs, 11.9 μs and 6.1 μs, 5.8 μs, respectively. The percentages of single, double, and triple strokes of lightning flashes were 83% (64 cases), 16% (12 cases), and 1% (1 case), respectively. The AM and GM of the interstroke intervals and the return stroke (RS) amplitude ratios were 163.9 ms, 0.29, and 13.3 ms, 0.26, respectively. Furthermore, it was also found that 7 (9%) of 77 positive CG flashes had double peak return stroke waveforms with AM and GM values for 0%–100% and 10%–90% rise time of subsequent return strokes that were 6.7 μs, 6.4 μs and 4.1 μs, 4 μs, respectively. We inferred that these double peaks are produced by two ground terminations with a time interval varying from 7 to 560 μs.
Highlights
Downward positive cloud to ground (CG) flashes constitute only about 10% of all ground flashes [1]
For negative CG flashes, several researchers have reported that the downward leaders with many branches are able to produce different ground terminations, which are separated by several tens to hundreds of meters [6,7,8,9,10,11,12]
This paper reports an investigation of return stroke characteristics of positive CG lightning flashes, such as rise time, number of return stroke, interstroke interval and subsequent to first return stroke amplitude ratio in the tropics of Indonesia
Summary
Downward positive cloud to ground (CG) flashes constitute only about 10% of all ground flashes [1]. Positive lightning flashes may lead to more damage to electric power and telecommunication systems than negative lightning flashes. They have properties that are different from those of negative lightning flashes, such as high peak current, and differences in the number of strokes per flash, continuing current, charge transfer, leader propagation, and branch patterns [2,3,4,5]. For negative CG flashes, several researchers have reported that the downward leaders with many branches are able to produce different ground terminations, which are separated by several tens to hundreds of meters [6,7,8,9,10,11,12]. To identify strokes producing multiple ground terminations, return stroke parameters such as rise time, interstroke interval, and amplitude ratio need to be examined
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