#astronomy Juno Discovers Sprites and Elves on Jupiter – Sky & Telescope

October 29, 2020 - Comment

NASA’s Juno spacecraft has detected transient, 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 generally be seen excessive above highly effective lightning discharges. A sprite — a shiny, transient, flash


NASA’s Juno spacecraft has detected transient, 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 generally be seen excessive above highly effective lightning discharges.

A Jovian spriteA sprite — a shiny, transient, 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 information 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 may be very opaque to ultraviolet radiation, so the flashes should originate a lot greater” than the planet’s ammonium-rich thunderclouds, she says — in all probability some 260 kilometers (160 miles) above the 1-bar strain stage within the environment.

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

In in the present day’s Journal of Geophysical Analysis: Planets, Giles and her colleagues argue that the flashes are in all probability 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 have been solely caught on digicam for the primary time in 1989. They’re brought on by electromagnetic disturbances, generated by energetic lightning shows. Not like on Earth, although, Jovian TLEs are usually 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 EarthThe uncommon atmospheric phenomenon generally known as sprites seem purple when captured above Earth.
Jesper Grønne / S&T On-line Photograph Gallery

Again in 2009, a crew led by Yoav Yair (Open College of Israel) predicted what TLEs within the environment of different planets would appear like. In accordance with Giles, the UV flashes noticed by Juno meet all of the expectations for Jovian sprites. Yair’s coauthor Ute Ebert (Eindhoven College of Know-how, the Netherlands) says it appears like “a lovely affirmation” of the predictions. “We additionally need to examine the function of planetary magnetic fields,” she says. That is likely to be simpler if TLEs might 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 sorts of measurements, says Giles, so the crew wants a special method.

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

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