Toward a better understanding of negative lightning stepped leaders

Negative lightning leaders observed at very close (within a few kilometers) distances often exhibit heavy branching with many active tips forming network‐like structure descending multi-tip “ionization front” whose transverse dimensions are of the order hundreds meters. The presence such front makes attachment process more complex than usually assumed. leader branches extend in step-like manner, each step necessarily generating traveling wave moving positive charge from branch tip up along channel, like mini return stroke. stepping has number generally unrecognized consequences. Specifically, stepped-leader can collide lateral surface an adjacent (usually angle about 90°). Further, step‐related positive-charge waves propagating channel reactivate decayed negative higher altitudes. Overall, heavily-branched stepped creates highly-structured and rapidly-changing electric field pattern inside vicinity volume it occupies, which causes interactions between branches.