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 cloudto-ground strokes which had attained exceptionally large charge moment (charge times height) changes of 39006100 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.