Microwave and Very High Frequency Radiations of The First Narrow Initial Breakdown

Abstract

This paper reports the observation of microwave and very high frequency (VHF) radiation pulses associated with the first narrow (<10us) initial breakdown (IB) pulses of ten negative cloud-to-ground (-CG) flashes. The centre frequency of microwave and VHF sensors was 0.97 GHz and 60 MHz, respectively. We found that all microwave pulses were the initiation event led the first VHF pulses ranging between 0.03187 and 2.57968 µs and led the first narrow IB pulses ranging between 0.02382 and 2.70202 µs. Half of the VHF pulses were observed to lead the first narrow IB pulses ranging between 0.03453 and 0.128 µs. Moreover, polarity of microwave radiation pulses was always positive while the polarity of the first narrow IB pulses always negative. On the other hand, half of VHF radiation pulses had the same polarity as microwave radiation pulses.