Space station detectors found the source of weird ‘blue jet’ lightning
The International Space Station spotted an exotic type of upside-down lightning called a blue jet (illustrated) zipping up from a thundercloud into the stratosphere in 2019.
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.
Cameras and light-sensing instruments called photometers on the space station observed the blue jet in a storm over the Pacific Ocean, near the island of Nauru, in February 2019. “The whole thing starts with what I think of as a blue bang,” says Torsten Neubert, an atmospheric physicist at the Technical University of Denmark in Kongens Lyngby. That “blue bang” was a 10-microsecond flash of bright blue light near the top of the cloud, about 16 kilometers high. From that flashpoint, a blue jet shot up into the stratosphere, climbing as high as about 52 kilometers over several hundred milliseconds.
The spark that generated the blue jet may have been a special kind of short-range electric discharge inside the thundercloud, Neubert says. Normal lightning bolts are formed by discharges between oppositely charged regions of a cloud — or a cloud and the ground — many kilometers apart. But turbulent mixing high in a cloud may bring oppositely charged regions within about a kilometer of each other, creating very short but powerful bursts of electric current, Neubert says. Researchers have seen evidence of such high-energy, short-range discharges in pulses of radio waves from thunderstorms detected by ground-based antennas.
Blue jets studied from Space Station
For years, their existence has been debated: elusive electrical discharges in the upper atmosphere that sport names such as red sprites, blue jets, pixies and elves. Reported by pilots, they are difficult to study as they occur above thunderstorms.
ESA astronaut Andreas Mogensen during his mission on the International Space Station in 2015 was asked to take pictures over thunderstorms with the most sensitive camera on the orbiting outpost to look for these brief features.
Denmark’s National Space Institute has now published the results, confirming many kilometre-wide blue flashes around 18 km altitude, including a pulsating blue jet reaching 40 km. A video recorded by Andreas as he flew over the Bay of Bengal at 28 800 km/h on the Station shows the electrical phenomena clearly – a first of its kind.
Satellites had probed these events but their viewing angle is not ideal for gathering data on the scale of the blue jets and smaller blue discharges. In contrast, the Station’s lower orbit is ideally placed to capture the sprites and jets.
Andreas aimed for cloud turrets – cloud pillars extending into the upper atmosphere – and shot a 160 second video showing 245 blue flashes from the top of a turret that drifted from the Bay of Bengal’s thunderstorm.
The blue discharges and jets are examples of a little-understood part of our atmosphere. Electrical storms reach into the stratosphere and have implications for how our atmosphere protects us from radiation.
This experiment confirms that the Space Station is a suitable base for observing these phenomena. As a follow-up, the Atmosphere–Space Interactions Monitor is being prepared for launch later this year for installation outside Europe’s Columbus laboratory to monitor thunderstorms continuously to gather information about such ‘transient luminous events’.
Andreas concludes, “It is not every day that you get to capture a new weather phenomenon on film, so I am very pleased with the result – but even more so that researchers will be able to investigate these intriguing thunderstorms in more detail soon.”
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