抄録
In this technical note, electromagnetic models of the lightning return stroke proposed as of today are reviewed and evaluated. In this class of models, using a numerical technique, Maxwell's equations are solved to yield the distribution of current along a vertical wire that represents the lightning return-stroke channel. Here, it is shown that a current wave necessarily suffers attenuation as it propagates upward along a vertical non-zero-thickness wire above perfectly conducting ground excited at its bottom by a lumped source, even if the wire has no ohmic losses, which is a distinctive feature of this class of models. Then, electromagnetic models proposed as of today are classified into six types depending on lightning-channel representation, and channel-current distributions and resultant electromagnetic fields calculated for these different channel representations are presented. Furthermore, methods of excitation, representative numerical techniques for solving Maxwell's equations, and applications of lightning return-stroke electromagnetic models are reviewed.
