Broadband ELF and VLF radio observations of rocket-triggered lightning

Abstract:

Naturally occurring radio events in the Earth-Ionosphere cavity have long been categorized by their signal content in the extremely low frequency (ELF, 3 Hz – 3 kHz) and very low frequency (VLF, 3 kHz – 30 kHz) radio bands. Recent past work has shown a strong connection between the occurrence of sprites and N-bursts, impulsive radio events that contain significant ELF and VLF energy. This paper presents evidence that shows cloud to ground (CG) lightning can also produce N-bursts. Several lightning flashes artificially triggered at the International Center for Lightning Research and Testing (ICLRT) during the 2016 summer season were detected at ELF and VLF receiver stations around the globe operated by the University of Florida. Distant ELF and VLF measurements are interpreted with the aid of on-site VLF records, channel-base current measurements, and lightning mapping array observations. In this paper, the relative spectral content in the ELF and VLF bands observed in distant waveforms are directly associated with variations in lightning source geometry and channel-base current properties.