Analysis of lightning strokes associated with sprites observed by ISUAL in the vicinity of North America


We examined the broadband (< 1 Hz to 30 kHz) lightning sferics associated with 395 sprites observed near North America by the Imager of Sprites and Upper Atmospheric Lightning (ISUAL) onboard the FORMOSAT-2 satellite in a 12-year period from 2004-2015. Our analysis indicates that the ISUAL dataset contains a significant fraction (69, or~ 18%) of negative sprites, which were predominantly (> 80%) observed over oceanic and coastal thunderstorms mostly in tropical areas. The mean and median of impulse charge moment change (iCMC) associated with positive (negative) sprites are+ 346 C km (-709 C km) and+ 280 C km (-649 C km), respectively. The morphology and parent lightning properties (eg, typically with high peak currents>-80 kA and large iCMCs>-300 C km) of negative sprites observed by the ISUAL are generally consistent with that documented in ground-based observations, but the ISUAL dataset does imply that sprites are sometimes produced by negative strokes with sub-critical iCMCs (less than-300 C km). Consequently, the future survey of global occurrence of sprites is desired to be based on complementary ground and space-borne observations.

Terrestrial Atmospheric and Oceanic Sciences