<b>Observations of Very Unusual Behavior of Lightning Discharges</b>

Based on recent observations at the Lightning Observatory in Gainesville (LOG), Florida, we present three examples of very unusual lightning behavior: (a) Two lightning discharges, one +CG and the other tower-terminated -CG separated by 11 km, were briefly coupled, so that positive charge was in effect drawn from the ground at the position of –CG and injected into the ground at the position of +CG. That unusual interaction was apparently accomplished by the initiation of M-component incident wave in the +CG channel by the leader of the first stroke of the –CG. (b) A branched positive leader intermittently extended via bidirectional transients separated by inactive intervals of about 5 ms, on average. The average overall extension speed of the positive leader was as low as 10³ to 10⁴ m/s. One of the bidirectional transients, moving negative charge in the backward direction, triggered a downward negative leader, resulting in a three-stroke –CG. (c) A subsequent-stroke negative leader, moving through virgin air, entered the lower part of residual (non-luminous) first-stroke channel, in addition to creating a new ground termination point. That subsequent leader was imaged up to 2.3 km above ground level, exhibited profuse branching, and collided with the defunct channel of the preceding first stroke at an altitude of about 90 m. Studying unusual lightning behavior helps to improve our understanding of the variability of basic lightning processes (still not fully understood) and to identify new potential lightning hazards to various objects and systems.