SOME PROPERTIES OF NEGATIVE CLOUD-TO-GROUND LIGHTNING FLASHES VERSUS STROKE ORDER

The return stroke initial electric field peak normalized to 100 km, the probability of creating a new termination on ground, and the probability of occurrence of a dart-stepped leader after an interstroke interval of 100 ms or less have been determined as a function of stroke order from simultaneous electric field and TV records of 76 negative cloud-to-ground flashes near Tampa, Florida. Fifty percent of the flashes showed multiple terminations on the ground as inferred from TV records (from 29 to 69 percent for separate thunderstorm days). For all flashes, the minimum initial electric field peak normalized to 100 km for first strokes was found to be 2.2 V/m and for subsequent strokes 0.25 V/m. The geometric mean initial electric field peak for 155 second, third and fourth strokes taken together was found to be 1.4 times larger than for 115 strokes of order 5 through 18, with the difference being statistically significant at the 0.005 significance level. -from Authors