The Reactivation of Decayed Positive Leader With Sudden Channel Elongation in Laboratory Long Spark

Abstract Positive lightning leaders present reactivation behaviors during their propagation processes. The mechanism underlying the reactivation of positive leaders is yet unclear. Using the synchronous measurement of optical observation, discharge voltage, and current, a novel phenomenon related to the reactivation of positive leaders is reported in laboratory. It is disclosed that separate luminous structures, which lead to positive leader steps, can form ahead of decayed leaders. The single positive leader branch can be reactivated by a separate luminous structure accompanied by a steep‐rising current pulse superimposed on zero background current. When positive leaders show decayed branches during their development, separate luminous structures can reactivate decayed branches and result in alternating and competitive development among branches. This process is accompanied by a sudden elongation in length. The reactivation scenario reported here in laboratory helps to interpret that in natural lightning.