負極性下向きステップトリーダの継続時間と第一帰還雷撃の電流波高値との相関

抄録

The authors have observed E-field waveforms of lightning discharges and estimated duration of negative downward stepped leader by measuring time interval between onsets of preliminary breakdown pulses and the following first return stroke. 334 examples obtained in Sagamihara city on six days of summer in 2015 are subject to an analysis. Mean and median durations of negative downward stepped leader measured by our observations were 29.7 ms and 22.0 ms, respectively. We found out that there were correlations between duration of negative downward stepped leader and peak current of the following first return stroke estimated by the JLDN. The duration of negative downward stepped leader became short when absolute value of estimated peak current of first return stroke became large. The time interval of the leader pulse in the E-field waveform did not depend on the current amplitude of the following first stroke, therefore, the above-mentioned result might be due to the increase of the step length of the leader with the increase of the current amplitude of the following first return stroke.