Scientists have finally gotten a clear view of the spark that triggers a type of exotic lightning called blue jet.
Blue jets zip upward from thunderstorm clouds into the stratosphere, reaching altitudes of about 50 kilometers in less than a second. While a common ray excites a mixture of gases in the lower atmosphere to glow white, blue jets excite mainly stratospheric nitrogen to create its blue hue.
Blue planes have been observed from the ground and planes for years, but it’s hard to tell how they form without being above the clouds. Now, International Space Station instruments have detected a blue jet emerging from a very brief, bright explosion of electricity near the top of a cloud of thunder, according to online researchers on Jan. 20 in Nature.
It is important to understand blue jets and other storm-related phenomena in the upper atmosphere, such as sprites (SN: 14/06/02) and elves (SN: 23/12/95), because these events can affect how Radio waves travel through the air that can have an impact on communication technologies, says Penn State space physicist Victor Pasko, who did not participate in the work.
Cameras and light detection instruments called photometers at the space station observed the blue jet in a storm over the Pacific Ocean near the island of Nauru in February 2019. "It all starts with what I think of as a blue explosion." says Torsten Neubert, an atmospheric physicist at the Technical University of Denmark in Kongens Lyngby. That “blue blow” was a flash of bright blue light 10 microseconds near the top of the cloud, about 16 miles high. From that flashpoint, a blue jet fired into the stratosphere, rising to about 52 miles over several hundred milliseconds.
The spark that generated the blue jet may have been a special type of short-range electric shock inside the cloud of thunder, Neubert says. Normal lightning is formed by discharges between oppositely charged regions of a cloud – or a cloud and the ground – many miles away. But the turbulent mixture high in a cloud can cause regions charged opposite each other about a mile apart, creating very short but powerful gusts of electric current, Neubert says. Researchers have seen evidence of these short-range high-energy discharges in pulses of radio waves from thunderstorms detected by terrestrial antennas.