BURSTS OF PULSES IN LIGHTNING ELECTROMAGNETIC-RADIATION - OBSERVATIONS AND IMPLICATIONS FOR LIGHTNING TEST STANDARDS

Bursts of regular microsecond-scale electric field pulses produced by three multiple-stroke cloud-to-ground discharges (a total of 2782 puls es) and by three cloud discharges (a total of 1436 pulses), all record ed within 20 km or so at the NASA Kennedy Space Center, are analyzed, The regular pulse bursts are similar in both cloud-to-ground and cloud discharges, A burst is characterized by some tens of pulses, each hav ing a total width of a few microseconds, with an average interpulse in terval of 6-7 mu s. Pulse peaks in cloud-to-ground discharges are appr oximately two orders of magnitude smaller than return-stroke initial f ield peaks in the same flash, In both cloud and ground discharges, the re is a tendency for the bursts to occur in the latter stages of a dis charge, and positive and negative pulse polarities are about equally p robable, Many bursts were found to be associated with the latter part of K changes while one pronounced M change appeared to be initiated by a regular pulse burst, The observed regular pulse bursts exhibit some similarity to the ''multiple burst'' (component H) of the standard li ghtning environment for the design and testing of aerospace vehicles [ 1], Overall, neither the present definition of the H component given i n [1] nor its newly proposed revision appears to be based on adequate experimental data.