Ionospheric elves powered by corona discharges in overshooting thunderclouds

Abstract Elves are rapidly expanding rings of optical emissions in the lower ionosphere, excited by the transient electromagnetic pulses from lightning in the clouds below. Narrow bipolar events (NBEs) are signatures in radio signals from intra-cloud discharges. They are thought to be fast streamer breakdown that may trigger the onset of lightning and blue jets. Recent observations from space suggest they may carry sufficient current to excite elves. Here, we report the first simultaneous observation of NBEs and elves that confirm this hypothesis. Three negative NBEs produced in a tropical storm are observed from the ground by a radio wave receiver located in China and their optical signatures from space by the Atmosphere-Space Interactions Monitor (ASIM) on the International Space Station (ISS). The NBEs are associated with flashes of emissions in N22P at 337 nm, with faint or no activity in the dominant lightning leader line OI at 777.4 nm, confirming their streamer nature. The elves are seen as delayed emissions in the near-ultraviolet of the Lyman–Birge–Hopfield (LBH) band. Our analysis suggests that negative NBE discharges can generate weak, but observable elves when the associated impulse current is above ~ 140 kA. The appearance of elves would provide a new method to estimate the currents of corona discharges at cloud tops, crucial for the characterization of chemical perturbations to greenhouse gas agents at the tropical tropopause.