MEASUREMENTS OF LIGHTNING RADIATION FIELD AND ESTIMATION OF FIRST RETURN STROKE PARAMETERS

This paper briefs a method of measuring lightning radiation field with a fast antenna and narrow bandwid threceivers,the first return stroke parameters and the spectrum distribution from 2 kHz to 20 MHz for both ground discharges and cloud discharges are calculated.The peak radiation field of first return stroke,normalized to 50 km,is (15.2±8.4)V/m.Below 1 MHz,the total energy radiated by the first return stroke is (0.8±1.6)×105J,the peak power is (0.8±1.0)×1010W,the peak current is(27.8±17.1) kA,and the peak current derivation is (109.3±91.5) kA/μs.The peak spectral amplitudes appear between 4 kHz to 10 kHz for ground discharges and 20 kHz to 80 kHz for cloud discharges.From 10 kHz to 3.0 MHz,the spectral amplitudes of the ground discharges decrease in 1/f,and from 3.0 MHz to 20 MHz,in 1/f2.Below 40 kHz,the ground discharge is the main lightning radiation source;and above 40 kHz,both discharges behave similarly.A few special phenomena were found and explained preliminarily.