Researchers have finally gotten a clear view of the trigger that sets off an unique type of lightning called a blue jet.

Blue jets zip up from thunderclouds into the stratosphere, reaching altitudes approximately about 50 kilometers in less than a second. Whereas common lightning excites a collection of gases in the lower environment to glow white, blue jets excite mainly dizzying nitrogen to create their signature blue color.

Blue jets have been observed from the ground and airplane for years, but it’s tough to inform how they form without getting high above the clouds. Now, instruments on the International Space Station have actually spotted a blue jet emerge from an extremely quick, intense burst of electrical power near the top of a thundercloud, researchers report online January 20 in Nature

Understanding blue jets and other upper-atmosphere phenomena associated with thunderstorms, such as sprites ( SN: 6/14/02) and elves ( SN: 12/23/95), is important because these occasions can impact how radio waves travel through the air– possibly affecting interaction technologies, says Penn State space physicist Victor Pasko, who was not involved in the work.

Cameras and light-sensing instruments called photometers on the spaceport station observed the blue jet in a storm over the Pacific Ocean, near the island of Nauru, in February2019 “The whole thing starts with what I think of as a blue bang,” states Torsten Neubert, a climatic physicist at the Technical University of Denmark in Kongens Lyngby. That “blue bang” was a 10- microsecond flash of brilliant blue light near the top of the cloud, about 16 kilometers high. From that flashpoint, a blue jet soared into the stratosphere, climbing up as high as about 52 kilometers over several hundred milliseconds.

The spark that generated the blue jet may have been a special type of short-range electrical discharge inside the thundercloud, Neubert says. Normal lightning bolts are formed by discharges in between oppositely charged areas of a cloud– or a cloud and the ground– many kilometers apart. Turbulent mixing high in a cloud might bring oppositely charged regions within about a kilometer of each other, creating very brief however effective bursts of electric current, Neubert states. Researchers have seen proof of such high-energy, short-range discharges in pulses of radio waves from thunderstorms identified by ground-based antennas.


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