Detection of daytime sprites via a unique sprite ELF signature

On August 14, 1998, 3 separate daytime sprite events were detected via a unique extremely low frequency (ELF) sprite signature. The onset of the sprite ELF signatures was delayed by 11.0–13.2 ms from positive cloud‐to‐ground strokes which had attained exceptionally large charge moment (charge times height) changes of 3900–6100 C·km. It is shown that a charge moment change of 6100 C·km may have been sufficient for conventional breakdown at ≃54 km altitude, assuming an experimentally measured ion conductivity profile of Holzworth et al. , [1985]. The daytime sprites themselves contained unusually large charge moment changes of ≃2800 C·km, ≃1200 C·km, and ≃910 C·km.