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Juno Discovers Sprites and Elves on Jupiter – Sky & Telescope

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NASA’s Juno spacecraft has detected temporary, highly effective flashes of ultraviolet mild within the higher environment of Jupiter. They’re believed to be the Jovian counterparts of sprites and elves on Earth — electrical phenomena within the environment that may typically be seen excessive above highly effective lightning discharges.

A Jovian sprite
A sprite — a vibrant, temporary, flash — is circled in yellow on this ultraviolet picture of Jupiter’s south pole from NASA’s Juno spacecraft. The UV picture additionally captures the auroral ring across the pole, in addition to the magnetic “footprint” of the moon Io.
NASA / JPL-Caltech / SwRI

Scientists discovered the flashes in knowledge from Juno’s ultraviolet imaging spectrograph, Rohini Giles (Southwest Analysis Institute) informed the digital assembly of the Division of Planetary Sciences (DPS) on October 27th. Between August 2016 and July 2020, Juno noticed a complete of 11 UV flashes.

They’ll’t be lightning bolts themselves, explains Giles. “Jupiter’s environment could be very opaque to ultraviolet radiation, so the flashes should originate a lot greater” than the planet’s ammonium-rich thunderclouds, she says — most likely some 260 kilometers (160 miles) above the 1-bar strain degree within the environment.

Every flash lasts for just some milliseconds and appears like a degree supply to Juno, which implies the supply can’t be bigger than 1,000 kilometers throughout or so. The flashes happen above turbulent areas within the environment recognized to host thunderstorms.

In at present’s Journal of Geophysical Research: Planets, Giles and her colleagues argue that the flashes are most likely much like sprites and elves, labeling them transient luminous occasions (TLEs). These have by the way been noticed above terrestrial thunderclouds for many years however had been solely caught on digicam for the primary time in 1989. They’re attributable to electromagnetic disturbances, generated by energetic lightning shows. In contrast to on Earth, although, Jovian TLEs usually are not simply seen at optical wavelengths, since they’re produced by the excitation of molecular hydrogen (H2) as a substitute of molecular nitrogen (N2).

Red sprites above Earth
The uncommon atmospheric phenomenon often called sprites seem purple when captured above Earth.
Jesper Grønne / S&T Online Photo Gallery

Again in 2009, a group led by Yoav Yair (Open College of Israel) predicted what TLEs within the environment of different planets would appear to be. In line with Giles, the UV flashes noticed by Juno meet all of the expectations for Jovian sprites. Yair’s coauthor Ute Ebert (Eindhoven College of Expertise, the Netherlands) says it seems like “a fantastic affirmation” of the predictions. “We additionally need to examine the function of planetary magnetic fields,” she says. That could be simpler if TLEs will be studied on totally different planets.

Nevertheless, one prediction hasn’t but been examined: Juno can’t test whether or not the ultraviolet flashes happen concurrently with optical lightning discharges, as a result of its UV and visible-light devices are mounted on totally different sides of the triangular, spinning spacecraft. This design ends in a 10-second offset between the 2 varieties of measurements, says Giles, so the group wants a unique strategy.

“Our greatest hope is the Waves instrument, which research radio and plasma waves,” she says. “The very strongest discharges may presumably produce longer-lasting waves.”


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