RATIO OF FIRST TO SUBSEQUENT RETURN STROKE ELECTRIC FIELD PEAKS IN NEGATIVE CLOUD-TO-GROUND LIGHTNING DISCHARGES

Abstract- We examine relative magnitudes of electric field peaks of first and subsequent return strokes in 176 multiple-stroke negative cloud-to-ground lightning flashes recorded during two storms in summer 2006 in Gainesville, Florida. The arithmetic and geometric means of the ratio of the first to subsequent return stroke field peaks are 2.1 and 1.7, respectively. Thus, on average, the electric field peak of the first stroke is significantly (roughly 2 times) larger than the field peak of the subsequent stroke, which is consistent with the previous studies of first versus subsequent stroke intensity in Florida [Rakov and Uman, 1990a, b]. The arithmetic and geometric mean ratios of the subsequent to corresponding first return stroke electric field peaks have been found to be equal to 0.75 and 0.58, respectively. Additionally, we review previously published ratios of subsequent to first stroke electric field or current peaks (and their inverses) for other locations, which are generally consistent with our results