ELF/VLF Radio Bursts Associated With Transient Luminous Events: Radio Metrics

Abstract Extremely low‐frequency (ELF, 33,000 Hz) and very low frequency (VLF, 330 kHz) radio impulses known as ELF/VLF transients have been observed for over 80 years and have been closely associated with lightning and lightning‐related phenomena. Observations of ELF/VLF radio transients performed by the University of Florida's global ELF/VLF receiver network are used to determine quantitative metrics by which to characterize the ELF/VLF transients as Q‐bursts and N‐bursts. As a result of this effort, a new type of transient is identified and deemed the VO‐burst. These metrics are used to analyze the ELF/VLF transients observed simultaneously with ground‐based amateur optical observations of sprites and gigantic jets. Four case studies support the conclusions that sprites are associated with N‐bursts, whereas gigantic jets are associated with Q‐bursts. Additional observations performed during rocket‐triggered lightning experiments at Camp Blanding, Florida, suggest that typical cloud‐to‐ground lightning return strokes are associated with VO‐bursts, which do not exhibit any significant ELF component. While these new radio metrics can be employed to automatically process ELF/VLF transient observations to distinguish between Q‐bursts, N‐bursts, and VO‐bursts, we propose that this additional quantitative characterization of radio bursts could also be employed to detect and distinguish between various types of transient luminous events, but more observations are required to rigorously establish this relationship.