A pocket discharge model for narrow bipolar events and possible applications

Narrow bipolar events refer to a distinct type of in-cloud lightning discharge which produces electric field of bipolar and impulse in nature. In this presentation narrow bipolar events were considered as the discharge of the pocket charge to the charge layer inside thundercloud, and the current wave-shape possibly responsible for the narrow bipolar electromagnetic field was featured by two channel-conducting-state depended parameters (α,β). The parameter β inversely reflects the time for the current front to propagate along the channel and can be achieved by the perfect fit of the measured field waveform to the model field waveform with the channel length and current propagation speed bound by the parameter β. The present model was applied to the narrow bipolar fields of two narrow bipolar events to reach a parameter β of 0.333 μs^-1 and 0.353 μs^-1 respectively, indicating a channel length less than 1km.