A Macro-Physical Model for Narrow Bipolar Events

Narrow bipolar events (NBEs) refer to a type of characteristic electric field signatures produced by high-power intracloud discharges. The physical mechanisms of NBEs remain unclear due to observational limitations. In this paper, we present a macro-physical model for NBE based on the time domain electric field integral equation (TD-EFIE) to better understand the processes underlying NBEs. The NBE is modeled as a transient breakdown process triggered randomly by a local weak corona discharge in an intense ambient electric field generated between two opposite spheric distributed charges. For a given ambient electric field profile, the model can self-consistently simulate the channel behavior, including the charge transfer, nonlinear variation of conductance, and current evolution. The distant vertical electric field generated by the breakdown process is then calculated and compared with the characteristic observed for NBE pulses. It is found that by adjusting the ambient electric field profile, the signatures of electric field pulses of various type NBEs could be reasonably simulated.