On the Electric Field-change due to the Leader Processes and Some of Their Discharge Mechanism

Field-changes due to lightn i ng discharges are investigated by simultaneous recording by means of electrostatic fluxmeter and amplifier oscillograph. It has been made clear that the leader to the 1st return stroke is always a stepped leader, because successive pulses having regular intervals corresponding to those of the stepped leader are always recorded in the 1st leader field-change of the ground flash. The most frequent pulse intervals are 40∼60 m-sec; they are generally longer in the initial part and gradually become shorter towards the final part where they heve the minimum value of 13 μ-sec immediately before the return stroke. The leader field-change preceding the successive rapid change also contains a succession of pulses having the uniform interval of 13 μ-sec, and consequently the dart leader is considered to progress with some stepping processes repeated with this short time interval. It can be concluded that the negative streamers such as stepped and dart leaders progress with some stepping processes which cause a succession of pulses in its electric fieldchange.