Optical emissions associated with narrow bipolar events from thunderstorm clouds penetrating into the stratosphere

Abstract

Narrow bipolar events (NBEs) are signatures in radio signals from thunderstorms observed by ground-based receivers. NBEs may occur at the onset of lightning, but the discharge process is not well understood. Here, we present spectral measurements by the Atmosphere‐Space Interactions Monitor (ASIM) on the International Space Station that are associated with nine negative and three positive NBEs observed by a ground‐based array of receivers. We found that both polarities NBEs are associated with emissions at 337 nm with weak or no detectable emissions at 777.4 nm, suggesting that NBEs are associated with streamer breakdown. The rise times of the emissions for negative NBEs are about 10 μs, consistent with source locations at cloud tops where photons undergo little scattering by cloud particles, and for positive NBEs are ~1 ms, consistent with locations deeper in the clouds. For negative NBEs, the emission strength is almost linearly correlated with the peak current of the associated NBEs. Our findings suggest that ground-based observations of radio signals provide a new means to measure the occurrences and strength of cloud-top discharges near the tropopause.

Global Distribution of Key Features of Streamer Corona Discharges in Thunderclouds

“…Recent airborne observations (Brune et al, 2021) and laboratory experimental results (Jenkins et al, 2021) indicate that considerable amounts of oxidant species (OH, HO 2 ) could be directly produced by visible and subvisible (corona) electrical discharges in thunderstorm anvils and not only be the indirect result of atmospheric chemical processes after the injection of lightning NO x (Finney et al, 2016;Gordillo-Vázquez et al, 2019;Schumann & Huntrieser, 2007). The production of OH and HO 2 recently reported by Jenkins et al (2021) could also be due to air plasma streamers in corona discharges occurring in thunderstorm anvils (Bozem et al, 2014;Minschwaner et al, 2008;Pérez-Invernón et al, 2019;Zahn et al, 2002) since thundercloud coronas (Li et al, 2021;Liu, Lu, Neubert, et al, 2021;Soler et al, 2020) are now known to be more frequent (about 10 per s worldwide) (Soler et al, 2021) than previously suspected. Corona discharges in thunderclouds are especially frequent in the Tornado alley in North America (Soler et al, 2021) where airborne observations by Brune et al (2021) have recently reported significant regional transient enhancements of OH and HO 2 concentrations during thundercloud electrical activity.…”

Observations of Blue Corona Discharges in Thunderclouds

“…This is further suggested by the large proportion of fast and slow blue discharges associated with overshooting tops. NBEs are often associated with overshooting tops and severe weather which is supported by the data presented here (Liu et al., 2021; Monette et al., 2012).…”

Multi‐Pulse Corona Discharges in Thunderclouds Observed in Optical and Radio Bands

“…Most of this knowledge about NBEs and fast breakdown derives from radio observations but these have been recently complemented by optical detections from space. The Modular Multispectral Imaging Array (MMIA) instrument of the Atmosphere‐Space Interactions Monitor (ASIM), operating since 2018 from the International Space Station (ISS), has detected a large number of Blue LUminous Events (BLUEs) globally (Soler et al., 2021), which are optical pulses with a strong 337 nm signal, associated with streamer discharges, but lacking the 777 nm emissions that would indicate the presence of a hot leader (Li et al., 2021; F. Liu, Lu, et al., 2021; Soler et al., 2020). Combined radio and optical studies have found that NBEs often have a BLUE counterpart (Li et al., 2021; F. Liu, Lu, et al., 2021; Soler et al., 2020).…”