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

  • Author(s): Gaopeng Lu, Steven A. Cummer, Alfred B. Chen, Fanchao Lyu, Dongshuai Li, Fei Liu, Rue-Ron Hsu, and Han-Tzong Su
  • DOI: 10.3319/TAO.2017.03.31.01
  • Keywords: Cloud-to-ground (CG) lightning stroke, Negative sprite, Space observation, Impulse charge moment change (iCMC)
  • Significant percentage of negative sprites in the ISUAL dataset
  • Analysis of iCMCs associated with ISUAL sprites on a statistical basis
  • Population of negative sprites over oceans and coastal areas

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 to 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 (e.g., 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.

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