On polarity asymmetry of the occurrence rate of sprite discharges

From a recent statistical analysis of the transient luminous event called sprites, a strong lightning polarity asymmetry of their occurrence rate by 1000/1 (positive/negative) is proposed. Using the criteria with lightning charge moment and discharge time, we analyze the statistical data to estimate the positive/negative event ratio of sprites. We find that the ratio is about 150 based only on the criteria for lightning charge moment, whereas it increases up to be about 3000 considering the criterion of lightning discharge time. We would discuss importance of the latter criterion and the possible discharge time distribution.