Observations of Blue Corona Discharges in Thunderclouds

Abstract

Streamers are a type of electrical discharge characterized by a filament of weakly ionized plasma propagating as an ionisation wave. A multitude of streamers may be launched, for instance, from lightning leader tips, where their optical emissions form a corona. They pre-ionize and condition the atmosphere ahead of a lightning leader, assisting its continued propagation (Ebert et al., 2010;Raizer, 1980). Flashes of light from thunderstorm clouds have been observed in the second positive band of Nitrogen (N 2 2P) at 337 nm (blue) with no emission in the main lightning leader lines of OI at 777.4 nm (red), suggesting they are made of streamer breakdown. They are observed in the upper regions of clouds, with some at the very top (

Global Distribution of Key Features of Streamer Corona Discharges in Thunderclouds

“…The second group of single pulse BLUEs reaches longer rise times (up to ∼0.8 ms) and total times (up to ∼4 ms) associated with lower peak powers (≤50 μWm −2 ) and total brightnesses (∼25 μWm m −2 ). The two groups of BLUEs with fast (≤50 μs) and slow (>50 μs and up to ∼0.8-1.0 ms) rise times are consistent with those mentioned in Husbjerg et al (2022).…”

“…A variety of BLUEs including kilometer-scale blue discharges at the cloud top layer at ∼18 km altitude, blue starters and a pulsating blue jet propagating into the stratosphere were color photographed from the International Space Station (ISS) (Chanrion et al, 2017). BLUEs have also been recently observed by the nadir-pointing MMIA onboard ASIM in the ISS since April 2018 (Husbjerg et al, 2022;Li et al, 2021;Neubert et al, 2021;Soler et al, 2020). However, it is a known issue that powerful NBEs are highly likely to be misclassified or simply missed by lightning locating systems (Zhu et al, 2022).…”

Transition in Optical and Radio Features During the Early Development of Negative Intracloud Leader

“…First, if a leader channel forms, the detected 337 nm radiation was suggested to be able to well depict the leader channels in the stratiform regions with low cloud tops (Montanyà et al, 2021). Second, many authors have reported electrical activities from the top of cloud due to streamers only (Dimitriadou et al, 2022;Edens, 2011;Husbjerg et al, 2022;Li et al, 2022;Liu et al, 2021;Soler et al, 2020Soler et al, , 2021. The negligible 777.4 nm optical radiance implies the absence of leader channel formation.…”

Different Types of Corona Discharges Associated With High‐Altitude Positive Narrow Bipolar Events Nearby Cloud Top

“…Blue LUminous Events (BLUEs) are special Transient Luminous Events associated with thunderclouds that radiate intense near‐ultraviolet (UV) blue optical emissions dominated by 337 nm with weak or absent signals in the atomic oxygen line at 777.4 nm. They have also been termed as blue corona discharges in the recent studies (Dimitriadou et al., 2022; Husbjerg et al., 2022; Li et al., 2021; F. Liu, Lu, et al., 2021; F. Liu, Zhu, et al., 2021; Soler et al., 2020, 2021, 2022 ). They have similar features with different phenomena in other studies, such as blue starters/blue jets (Edens, 2011; Kuo et al., 2005; Wescott et al., 1996, 2001), BLEs (Chou et al., 2011, 2018; F. Liu et al., 2018), glimpses (Chanrion et al., 2017) and gnomes (also called Pixies ) (Lyons et al., 2003).…”

“…They have similar features with different phenomena in other studies, such as blue starters/blue jets (Edens, 2011; Kuo et al., 2005; Wescott et al., 1996, 2001), BLEs (Chou et al., 2011, 2018; F. Liu et al., 2018), glimpses (Chanrion et al., 2017) and gnomes (also called Pixies ) (Lyons et al., 2003). These optical signals normally last a few to hundreds of milliseconds and appear either isolated or in groups in the active thunderstorms, especially those with overshooting cloud tops and they occurred at the global frequency about 11 s −1 at local midnight (Chanrion et al., 2017; Chou et al., 2018; Dimitriadou et al., 2022; Edens, 2011; Husbjerg et al., 2022; Li, Neubert, et al., 2022; Li et al., 2021; F. Liu, Lu, et al., 2021; F. Liu, Zhu, et al., 2021; Lyons et al., 2003; Soler et al., 2021).…”