New insights into lightning returnstroke models with specified longitudinal current distribution

Abstract—We show that any lightning return-stroke model with specified longitudinal current distribution can be expressed, us-ing the appropriate continuity equation, in terms of two cur-rent components, propagation current and corona current. For lumped-current-source (LCS)-type (transmission-line-type) mod-els, the actual corona current is unipolar and directed radially out of the channel core, while for distributed-current-source (DCS)-type (traveling-current-source-type) models, it is also unipolar but directed into the channel core. The conversion between LCS and DCS return-stroke models alters the actual corona current (if any) of the model. A new formulation for LCS lightning return-stroke models is proposed using corona current and propagation cur-rent concepts. This formulation expresses the longitudinal current at height z ′ as the channel-base current minus the overall lon-gitudinal current change from ground surface to z′. Dynamics of lightning-channel corona sheath surrounding the thin channel core are examined based on LCS and DCS models. Index Terms—Continuity equation, corona sheath, distributed sources, lightning, lumped source, return-stroke model. I