Propagation Effects of Slanted Narrow Bipolar Events: A Rebounding-Wave Model Study

Narrow bipolar events (NBEs) are impulsive and powerful intracloud discharges. Recent observations indicate that some NBEs exhibit a slanted orientation rather than strictly vertical. However, the inclination of NBEs has not been considered in previous transmission line models, leading to uncertainty when evaluating their characteristics based on electromagnetic fields. This paper investigates the propagation effects of slanted NBEs using a newly developed slanted rebounding-wave model. It is found that the calculated results using the proposed model match well with measurements for both vertical and slanted NBE cases. The inclination of the NBEs significantly affects the electromagnetic fields at close distances, while the effects weaken as the observation distance increases, where the fields are dominated by the radiation component. The slanted rebounding-wave model improves the agreement with respect to a purely vertical channel and can be extended to any discharge geometry at arbitrary observation distances.