Lightning radiated electromagnetic fields and high voltage test specifications

The authors investigate the response of an F106-B aircraft, modeled by a lumped-parameter transmission line, to microsecond and submicrosecond impulses. Since a very high content of harmonics was observed for a submicrosecond impulse, the authors investigate the equation traditionally used for determining lightning current impulses from measured electric fields and correct this equation. It is found that the use of the zero-to-peak rate of rise of the order 230 kA/μs is unwarranted. Impulse voltages with risetimes on the order of 0.02 μs exert more severe stress on an aircraft structure than a 2-μs time-to-crest impulse. The harmonic components excited on the airframe have significant energy content in the HF spectrum. The crest voltage values along the structure of the aircraft may exceed the voltage impressed by the lightning electromagnetic pulse (LEMP) or the nuclear electromagnetic pulse (NEMP) due to the resonances excited on the airframe. The submicrosecond risetimes in the electric fields do not indicate submicrosecond time-to-crest values in the lightning currents