A review of positive and bipolar lightning discharges

Our knowledge of the physics of positive lightning remains much poorer than that of negative lightning. Many questions regarding the genesis of positive lightning and its properties cannot be answered without further research. It is worth noting that attempts to initiate positive lightning using the rocket-and-wire technique generally result in discharges that are composed of the initial stage (relatively low-level, long-lasting current component) that is not followed by positive leader/return-stroke sequences. Bipolar lightning is an even less understood and often unrecognized phenomenon. While some simple cloud charge distributions, such as a tilted dipole, an inverted dipole, or a positive monopole, can apparently explain the generation of positive lightning, the occurrence of bipolar lightning, as well as complex cloud discharges, suggests that the cloud charge structure cannot always be described by simple, vertically stacked charge models. It is likely that positively and negatively charged regions can exist at about the same height in the cloud.