An interesting paper potentially explaining a rare type of lighting, the Blue Jet.
Blue jets are lightning-like, atmospheric electric discharges of several hundred millisecond duration that fan into cones as they propagate from the top of thunderclouds into the stratosphere1. They are thought to initiate in an electric breakdown between the positively charged upper region of a cloud and a layer of negative charge at the cloud boundary and in the air above. The breakdown forms a leader that transitions into streamers2 when propagating upwards3.
However, the properties of the leader, and the altitude to which it extends above the clouds, are not well characterized4. Blue millisecond flashes in cloud tops5,6 have previously been associated with narrow bipolar events7,8, which are 10- to 30-microsecond pulses in wideband electric field records, accompanied by bursts of intense radiation at 3 to 300 megahertz from discharges with short (inferred) channel lengths (less than one kilometre)9–11.
Here we report spectral measurements from the International Space Station, which offers an unimpeded view of thunderclouds, with 10-microsecond temporal resolution. We observe five intense, approximately 10-microsecond blue flashes from a thunderstorm cell. One flash initiates a pulsating blue jet to the stratopause (the interface between the stratosphere and the ionosphere). The observed flashes were accompanied by ‘elves’12 in the ionosphere. Emissions from lightning leaders in the red spectral band are faint and localized, suggesting that the flashes and the jet are streamer ionization waves, and that the leader elements at their origin are short and localized.
We propose that the microsecond flashes are the optical equivalent of negative narrow bipolar events observed in radio waves. These are known to initiate lightning within the cloud and to the ground, and blue lightning into the stratosphere, as reported here.
JANUARY 21, 2021 AT 1:12 PM
Scientists have finally gotten a clear view of the spark that sets off an exotic type of lightning called a blue jet.
Blue jets zip upward from thunderclouds into the stratosphere, reaching altitudes up to about 50 kilometers in less than a second. Whereas ordinary lightning excites a medley of gases in the lower atmosphere to glow white, blue jets excite mostly stratospheric nitrogen to create their signature blue hue.
Blue jets have been observed from the ground and aircraft for years, but it’s hard to tell how they form without getting high above the clouds. Now, instruments on the International Space Station have spotted a blue jet emerge from an extremely brief, bright burst of electricity near the top of a thundercloud, researchers report online January 20 in Nature.
Understanding blue jets and other upper-atmosphere phenomena related to thunderstorms, such as sprites (SN: 6/14/02) and elves (SN: 12/23/95), is important because these events can affect how radio waves travel through the air — potentially impacting communication technologies, says Penn State space physicist Victor Pasko, who was not involved in the work.
via Watts Up With That?
January 23, 2021 at 08:54PM