Characteristics of radiation of lightning discharge in LF band

We have been developing a LF sensor network, called Broadband Observation network for Lightning and Thunderstorm (BOLT), to image whole structure of lightning discharges in 3D. This paper documents initial results of BOLT source locations for further understanding of characteristics of LF radiations. Whole lightning flash of a cloud-to-cloud and a cloud-to-ground flashes, including preliminary breakdown pulses, negative leaders at both high and low altitudes, breakdown in negative charge region (NCR), and a pulse burst, are well imaged by the BOLT. Normalized radiation amplitudes of BOLT sources associated with negative leaders and breakdown in NCR do not differ so much, implying that most of BOLT sources in NCR might be associated with negative recoil leaders.