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A Comparative Study on the Discontinuous Luminosities of Two Upward Lightning Leaders With Opposite Polarities

We have performed a comparative study on the luminosity of 12 steps in an upward positive leader and eight steps in an upward negative leader recorded under similar conditions. Through analyzing their so‐called differential luminosity profiles along leader channels, we found that the steps of positive leaders can be classified into two types. The type I step luminosity is similar to the luminosity produced by a negative leader step and is generally featured with a rapid increase near the leader tip and accompanied by a backward propagation along the leader channel. The type II step is featured with continuous luminosity variation along the leader channel. No apparent backward propagation has been identified in the type II step luminosity of the positive leader. Based on these observations, we have discussed how the two types of steps of positive leaders are produced.