Just as our planet has impressive auroras, so do other planets of the solar system have their custom light shows.
Jupiter has some of the most powerful auroras in the Solar System. Though they are invisible to our eyes, they grow intensely in ultraviolet wavelengths.
Because Jupiter is hugely different from our planet, scientists are very interested in finding out what forms the impressive atmospheric light shows, and new analysis provided fresh clues!
The Juno orbiter helped observe the auroral dawn storm for the first time.
Jupiter’s auroras result from a constant rain of high-energy electrons, mainly stripped from Io’s atmosphere. They are sped up via magnetic field lines to Jupiter’s poles, where they meet gases found in the upper atmosphere and interact with them to produce a spectacular glow.
The phenomenon is different from Earth’s auroras, which result from particles from the solar wind.
Also, Jupiter’s auroras are permanent and behave in unique ways. One of the behaviours is a so-called dawn storm, an intense brightening and broadening of the aurora at dawn, initially observed in 1994.
However, those dawn storms begin on the night part of the pole, and they’d been able to observe them forming until NASA’s Juno probe arrived near the observable region of the planet.
Bertrand Bonfond, an astronomer of the University of Liège in Belgium, said that observing Jupiter’s aurora from our planet doesn’t permit us to see beyond the limb, into the night side of the planet’s poles.
“Explorations by other spacecraft – Voyager, Galileo, Cassini – happened from relatively large distances and did not fly over the poles, so they could not see the complete picture. That’s why the Juno data is a real game-changer, allowing us a better understanding of what is happening on the night side, where the dawn storms are born,” Bonfond added.
Dawn storms can be overwhelming. They begin on the planet’s night side, rotating into view as dawn breaks, turning Jupiter’s aurora into a blazing ultraviolet beacon, emitting hundreds of thousands of gigawatts worth of light, at least ten times more energy than a typical Jovian aurora emits. The auroras persist for hours before turning back to more normal energy levels.
As the two planets’ auroras are so different, the process that provokes the dawn storm was expected to be incomparable to most processes seen in Earth’s auroras.
However, the data from Juno’s ultraviolet spectrograph looked a lot like what scientists have seen before.
Zhonghua Yao, an astronomer of the University of Liege, said:
“When we looked at the whole dawn storm sequence, we couldn’t help but notice that the dawn storm auroras at Jupiter are very similar to a type of terrestrial auroras called substorms.”
Earth’s auroral substorms are quite the show. They happen when our planet’s magnetosphere interacts with electric currents, provoking an explosive release of energy into the ionosphere.
The energy then gets dissipated into a complex, vibrant aurora that can last for many hours.
Substorms are severely influenced by the solar wind and the orientation of the interplanetary magnetic field.
Interactions with the solar wind fuel our planet’s magnetosphere.
On the other hand, Jupiter is full of plasma stripped from Io, which is manipulated according to the planet’s location.
The team’s analysis claims that Jupiter’s auroral dawn storms are influenced by an over-spill of plasma from Io, instead of the solar wind. Still, the result is surprisingly the same, a change in the magnetosphere provoking a radiant release of energy.