EDt M,p.üOO LIGHTNING FIELD SPECTRA OBTAINED FROM AIRBORNE MEASUREMENTS

A WC-130 aircraft was used as an airborne platform for broadband electric and magnetic field sensors to measure the surface fields on the airframe from lightning strikes in li.r 7 35 km range. The waveforms were recorded digitally, with a «ample interval of 20 nsec and a time window of 164 microseconds. Since the aircraft was above 15,000 feet, and the lightning source was relatively nearby, the effects of ground propagation were minimised. Spectra have been obtained for the stepped leader, first return stroke, and subsequent return stroke over the frequency range 100 kHz to 20 MHz. These spectra are compared to published data of lightning field spectra obtained from ground-based measurements. With airframe resonances and field enhancement effects removed, the data have two primary applications: l; To add to the data base for the nearby lightning strike threat« .*nd 2, To infer characteristics of the stepped leader, first return stroke, and subsequent return stroke processes. Recommendations for these applications are presented.