Blue Flashes as Counterparts to Narrow Bipolar Events: the Optical Signal of Shallow In-Cloud Discharges

Abstract

General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. Users may download and print one copy of any publication from the public portal for the purpose of private study or research.  You may not further distribute the material or use it for any profit-making activity or commercial gain  You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Global Frequency and Geographical Distribution of Nighttime Streamer Corona Discharges (BLUEs) in Thunderclouds

“…Research results through the last 40 years indicate that, in addition to lightning, kilometer scale corona electrical discharges formed by hundreds of millions of streamers (Cooray et al., 2020; Li et al., 2021; N. Liu et al., 2019) are common in thunderclouds around the globe but their genesis (Le Vine, 1980; Neubert et al., 2021; Rison et al., 2016; Smith et al., 1999; Soler et al., 2020; Tilles et al., 2019), dynamics (Bandara et al., 2019, 2021; Jacobson & Heavner, 2005; Jacobson et al., 2013; Wiens et al., 2008) and probable atmospheric chemistry impact (Bozem et al., 2014; Gordillo‐Vázquez & Pérez‐Invernón, 2021; Minschwaner et al., 2008; Pérez‐Invernón et al., 2019; Shlanta & Moore, 1972; Simek, 2002; Zahn et al., 2002) remain to be well understood.…”

“…As presented in the introduction, based on what it is known about optical emissions of leaders and streamer coronas (Li et al., 2021; Neubert et al., 2021; Soler et al., 2020), and of MMIA photometer sensitivity and noise levels (Chanrion et al., 2019), an algorithm for identification of BLUEs was designed. The algorithm analyzed all the 337 nm/4 nm (blue) and 777.4 nm/5 nm (red) photometer events recorded by MMIA in the period of study.…”

“…The term Blue LUminous Events (BLUEs) can then be safely applied to in‐cloud and to (partially) emerged transient electrical discharges that emit pulses of light mostly blue, that is, it could include a small fraction of red and infrared optical emissions (600–900 nm). This definition includes blue jets and starters, but also positive and negative NBEs, which are the VLF/LF radio manifestation of in‐cloud streamer coronas (Cooray et al., 2020; Li et al., 2021; Liu et al., 2018; N. Liu et al., 2019; Rison et al., 2016; Soler et al., 2020; Tilles et al., 2019).…”

“…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 Modular Multispectral Imaging Array (MMIA) onboard Atmosphere‐Space Interaction Monitor (ASIM) in the ISS since April 2018 (Li et al., 2021; Neubert et al., 2021; Soler et al., 2020).…”

Altitude and polarity transitions of corona activity in thundercloud tops reaching the lower stratosphere

“…

Thunderclouds occasionally penetrate into the stratosphere, forcing the exchange of air masses between the troposphere and the stratosphere 1,2 . Observations from space have shown that blue corona discharges are often generated in such thundercloud tops 3,4,5,6 and are the optical manifestation of so-called Narrow Bipolar Events (NBEs) observed in radio signals 7,8,9 . They come with two polarities, the positive that brings net negative charge aloft, and the negative that brings negative charge towards the earth.

…”