ABSTRACT
Measurements of lightning electric field, E, and dE/dt signatures have been made near Tampa Bay, Florida, under conditions where the lightning locations were known and where the results were not significantly affected by the response time of the measuring system or groundwave propagation. The fast transitions found on the initial portion of return-stroke fields have 10–90% risetimes ranging from 40 to 200 ns, with a mean of 90 ns. The maximum field derivatives during return strokes range from 5 to 75 V/m(μs)-1 with a mean of 29 V/m(μs)-1 when normalized to a distance of 100 km. These field risetime and derivative values suggest that return-stroke currents contain large, submicrosecond components, and this in turn suggests that it may be necessary to reevaluate the possible effects of lightning and the performance of lightning-protection devices in many situations.
