VHF Emissions Prior to the Onset of Initial Electric Field Changes of Intracloud Flashes

Abstract

We present the observation of VHF impulses electric (E) field emissions found in two normal intracloud (IC) flashes accompanied by initial electric field changes (IECs) in a tropical thunderstorm. The data was collected on November $23 ^{\mathbf {rd}}$, 2017 (within reversal distance) to our lightning sensor in Malacca, Malaysia. The durations from the onset of IECs to the first initial breakdown (IB) pulse are range between 0.68 and 0.69 ms and the magnitudes of IECs are range between 0.18 and 0.50 V/m. Besides that, before the onset of IECs there is small pulses was detected for IC flash (Nov_67) same with the VHF impulse for both IC flash. It was detected earlier before the onset of IEC by 12.69 and $251.60 \mu \mathrm {s}$ for the VHF impulse.