Elve doublets and compact intracloud discharges

Abstract

AbstractWe present evidence of ionospheric optical signatures of lightning, known as elves, which sometimes occur in pairs separated in time by ∼80–160 μs. We demonstrate that these “elve doublets” are the ionospheric signature of compact intracloud discharges (CIDs), which are extremely powerful, compact discharges that are thought to occur near the tops of thunderclouds. In this paper, using simple geometric calculations and full electromagnetic simulations, we show that CIDs from altitudes 14–22 km explain the time delay observed in elve doublets, consistent with typical CID altitudes. Furthermore, we show that the relative brightness of the first and second elves in the doublet is likely related to the orientation of the CID, and angles of 5°– 20° with respect to the vertical are consistent with the observed brightness ratios.