First ground-based observations of sprites over southern Africa

Abstract

Sprites are the optical signatures of electrical discharges in the mesosphere triggered by large lightning strikes associated with thunderstorms. Since their discovery in the late 1980s, sprites have been observed extensively around the world, although very few observations of sprites from Africa have been documented in the literature. In this paper, we report the first ground-based recorded observations of sprites from South Africa. In 2 out of the 22 nights of observations (11 January and 2 February 2016), about 100 sprite elements were recorded from Sutherland in the Northern Cape, comprising different morphologies (carrot (55%), carrot/column (11%), unclassified (21%), column (13%)). The sprites were triggered by positive cloud-to-ground lightning strikes, which had an average peak value of ~74 kA and were observed at distances from ~400 km to 800 km. The estimated charge moment change of the lightning discharges associated with these events was in agreement with the threshold for dielectric breakdown of the mesosphere and correlates well with the observed sprite brightness.

Significance: 

• The first ground-based recording of sprite events over southern Africa.
• It is suggested that the intensity of the events is proportional to the lightning stroke current.