Credits: NASA/JPL-Caltech/SwRI
NASA’s Juno spacecraft may have captured some of the most fleeting phenomena associated with powerful lightning storms here on Earth—400 million miles away on Jupiter!
Nicknamed sprites and elves these amazingly brief yet beautiful flashes of light occur miles above powerful lightning discharges in thunderstorms. They’ve only fairly recently been well-documented on Earth through digital photography, and now there’s solid evidence—thanks to Juno, which has been orbiting Jupiter since 2016—that these transient luminous events (TLEs) also occur elsewhere in our Solar System.
Scientists found the flashes in data from Juno’s ultraviolet imaging spectrograph, Rohini Giles (Southwest Research Institute) told the virtual meeting of the Division of Planetary Sciences (DPS) on October 27th. Between August 2016 and July 2020, Juno saw a total of 11 UV flashes. (Source: Sky & Telescope).
From a NASA news release on October 27, 2020:
New results from NASA’s Juno mission at Jupiter suggest that either “sprites” or “elves” could be dancing in the upper atmosphere of the solar system’s largest planet. It is the first time these bright, unpredictable and extremely brief flashes of light — formally known as transient luminous events, or TLEs — have been observed on another world. The findings were published on Oct. 27, 2020, in the Journal of Geophysical Research: Planets.
Scientists predicted these bright, superfast flashes of light should also be present in Jupiter’s immense roiling atmosphere, but their existence remained theoretical. Then, in the summer of 2019, researchers working with data from Juno’s ultraviolet spectrograph instrument (UVS) discovered something unexpected: a bright, narrow streak of ultraviolet emission that disappeared in a flash.
“On Earth, sprites and elves appear reddish in color due to their interaction with nitrogen in the upper atmosphere. But on Jupiter, the upper atmosphere mostly consists of hydrogen, so they would likely appear either blue or pink.”
— Rohini Giles, a researcher on the Juno team and lead author of the research
“UVS was designed to characterize Jupiter’s beautiful northern and southern lights,” said [Rohini] Giles, a Juno scientist and the lead author of the paper. “But we discovered UVS images that not only showed Jovian aurora, but also a bright flash of UV light over in the corner where it wasn’t supposed to be. The more our team looked into it, the more we realized Juno may have detected a TLE on Jupiter.”
Almost resembling a jellyfish, sprites feature a central blob of light (on Earth, it’s 15 to 30 miles, or 24 to 48 kilometers, across), with long tendrils extending both down toward the ground and upward. Elves (short for Emission of Light and Very Low Frequency perturbations due to Electromagnetic Pulse Sources) appear as a flattened disk glowing in Earth’s upper atmosphere. They, too, brighten the sky for mere milliseconds but can grow larger than sprites – up to 200 miles (320 kilometers) across on Earth.
Their colors are distinctive as well. “On Earth, sprites and elves appear reddish in color due to their interaction with nitrogen in the upper atmosphere,” said Giles. “But on Jupiter, the upper atmosphere mostly consists of hydrogen, so they would likely appear either blue or pink.”
According to an article from Business Insider India Juno can’t 100% confirm that these events were triggered by lightning strikes because its lightning-detecting instrument is on the opposite side of the spacecraft from the UV instrument, and data was captured by each at least 10 seconds apart—too long to observe the same flash. But their high altitude, emission profile, and duration all point to TLEs.
These electrical phenomena have also been recently observed and studied from above the clouds on Earth from the Space Station, orbiting 260 miles up.
Want to see some great photography of terrestrial TLEs? Check out Paul M. Smith’s website and Twitter feed:
Lights in the Dark 
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