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Credit: NASA

Eerie flashes of light coming from Jupiter glow like space sprites and elves

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Oct 31, 2020, 9:43 PM EDT

If you’re looking for sprites or elves dancing in the forest after dark, you might be disappointed—but in a way, they do exist.

What are known as “sprites” and “elves” are actually Transient Luminous Events (TLEs) that emerge from the upper atmosphere when thunderstorms are brewing and lightning strikes. These phenomena might actually be weirder than the mythical creatures they were named for. While they do occur on Earth, they have now been discovered on Jupiter. Until now, their existence in the swirling Jovian clouds was only theoretical—no more than a fairy tale. Astronomers have finally observed what is likely to be a sprite after Juno beamed back some strange data from Jupiter’s turbulent atmosphere.

However unearthly, TLEs do happen above thunderclouds on Earth. This is why the Juno data was seen as possible evidence for an extraterrestrial sprite.

“TLEs occur high up in the atmosphere and are triggered by a lightning strike in an underlying thunderstorm,” Juno scientist Rohini Giles, who recently led a study published in Journal of Geophysical Research: Planets, told SYFY WIRE. “Sprites are formed when the lightning strike generates a quasi-electrostatic field high in the atmosphere, and elves are formed when the lightning strike causes an upward moving electromagnetic pulse. We think these broad mechanisms would be similar on Jupiter.”

In Earth’s ionosphere, just above the lower atmosphere, irregularities in the charged particles of gas otherwise known as plasma can trigger sprites. They can only form during thunderstorms but rarely appear. When they do, they look like some sort of bioluminescent cosmic jellyfish, glowing red with tentacles of light that reach both down to the ground and upward. Sprites on Earth can get to be up to 30 miles across. Elves (Emission of Light and Frequency perturbations due to Electromagnetic Pulse Sources) look more like UFOs than anything in The Lord of the Rings. They are luminous flat discs that light up the entire sky for just milliseconds, but can get as huge as 200 miles across in the fraction of a blink of an eye.

Juno data with a colorized image of what could be a sprite. Credit: NASA

 

“Jupiter and the Earth have different atmospheric compositions, electron distributions and magnetic fields, so comparing TLEs on the two planets provides additional information about how they form,” Giles said.

TLEs on our planet get their flaming red color from atmospheric nitrogen. Most of our atmosphere is made of nitrogen, and when the quasi-electrostatic fields and electromagnetic pulses that generate sprites and elves accelerate electrons up there, they crash into the nitrogen molecules and release a red emission. Jupiter’s are thought to glow blue or pink during a storm because its atmosphere is mostly hydrogen. While Juno data has not revealed the color of the supposed sprite that registered as an ultraviolet emission that vanished almost as fast as it materialized, it did reveal dominant hydrogen in that flash.

Giles and her team also noticed that this otherworldly light stood out from the other enormous bright events that were later determined to be megabolts of lightning. Juno’s ultraviolet spectrograph instrument (UVS) picked up a flash in an area above the clouds of Jupiter where no flash was expected to occur. Elves and sprites cannot happen unless lightning triggers them, but are not actually lightning in themselves. Astronomers only have indirect evidence of sprites being set off by lightning. This comes from observations of regions where lightning strikes often. Never mind that, at least on Earth, they have never been seen at the exact same time as a lightning bolt. What kind of sorcery is this?

“It’s possible to have lightning without sprites, but it’s not possible to have sprites without lightning,” said Giles. “This is why we really want to observe lightning at the same time as one of our bright flashes, because it would provide very strong evidence that what we’re seeing really are sprites or elves.”

Maybe some fairy tales really do come true.