CHARACTERISTICS OF THE ELECTRIC FIELDS PRODUCED BY NEGATIVE LEADER IN ONE THUNDERSTORM IN GUANGDONG

Characteristics of the electric fields produced by stepped and dart-stepped leaders 200μs just prior to the return strokes in negative lightning discharges to ground during a thunderstorm process have been analyzed by using data from broad band slow antenna with system of time resolution 0.08μs in Conghua area near Guangzhou. It has been found that the electric field produced by stepped leader could be divided into three types based on their characteristics between the last leader pulse and the return stroke for 44 negative ground lightning discharges. The average time interval between the successive leader pulses prior to the first return strokes was 15.8μs, with a standard deviation of 5.3μs, and that of dart-stepped leader pulses prior to the successive return strokes was 9.4 μs with a standard deviation of 5.5μs. The average time interval between the last leader pulse and the first return strokes was 12.7μs, with a standard deviation of 7.8μs. The ratio of the amplitude of the last leader pulse to that of the return stroke was 0.1, with a standard deviation of 0.04. A correlation between the amplitude of the last leader pulse and the return stroke radiation field peak has been observed. The correlation is interpreted by using the transmission line model of return stroke.