Just as Earth has spectacular auroras, so do other planets in the Solar System with their own versions of the atmospheric light show.
In fact, Jupiter has the most powerful auroras in the solar system: invisible to our eyes, but glowing brightly at ultraviolet wavelengths.
Because Jupiter is very different from Earth, scientists are deeply invested in learning what drives these incredible atmospheric phenomena and have just gotten a new clue. Thanks to the Juno orbit, we have now observed for the first time the appearance of the mysterious auroral storm of Jupiter.
Jupiter’s auroras are produced by a constant rain of high-energy electrons mostly removed from Io’s atmosphere. These accelerate along magnetic field lines to the poles of Jupiter, where they fall into the upper atmosphere and interact with the gases to produce a glow.
This is different from the auroras on Earth, which are produced by particles from the solar wind. Unlike Earth’s auroras, Jupiter’s auroras are permanent and can behave very differently.
One of these behaviors is the dawn storm: an intense clearing and widening of the aurora at dawn, first observed in 1994. However, these dawn storms begin in the nocturnal part of the dawn. stick and we could never have seen them forming. until NASA’s Juno spacecraft arrived on the scene.
“Observing Jupiter’s aurora from Earth does not allow us to see beyond the limb, towards the nocturnal side of Jupiter’s poles,” explained astronomer Bertrand Bonfond of the University of Liège in Belgium.
“Explorations of other spacecraft (Voyager, Galileo, Cassini) passed over relatively large distances and did not fly over the poles, so they could not see the full image. That is why Juno’s data is a a real change of game, which allows us to understand what is happening at night, where the storms of dawn are born. “
The appearance of a dawn storm. (NASA / JPL-Caltech / SwRI / UVS / ULiège / Bonfond)
Dawn storms are really something. They begin in the night band of the planet, turning in sight when dawn breaks, transforming Jupiter’s aurora into a fiery ultraviolet beacon, emitting hundreds to thousands of gigawatts of light, at least ten times more energy than the Jovian aurora. usual. They persist for a few hours before yielding to more normal energy levels.
Because the two planets have these differences between their auroras, the process generated by the dawn storm was expected to be different from any process seen at Earth’s auroras. Surprisingly, though, the data from Juno’s ultraviolet spectrograph seemed strangely familiar.
“When we examined the entire sequence of dawn storms, we couldn’t help but notice that the auroras of the dawn storm on Jupiter are very similar to a type of terrestrial aurora called subtermines,” he said. astronomer Zhonghua Yao of the University of Liege.
The auroral subtermines of the Earth are amazing to see. They occur when the Earth’s magnetosphere is disturbed by electric currents, resulting in an explosive release of energy into the ionosphere. There, the energy dissipates like a complex dancing dancer that can last several hours.
Storms are strongly influenced by the solar wind and the orientation of the interplanetary magnetic field. But the Earth’s magnetosphere is dominated by interactions with the solar wind; Jupiter’s is filled with plasma removed from Io, which is controlled by the location of the planet.
According to the team’s analysis, the auroral storms of Jupiter’s dawn are influenced by an excessive spill of plasma from Io, rather than the solar wind; but the result is the same, a disturbance of the magnetosphere that results in an explosive release of energy.
In both cases, the accumulation of plasma and energy gradually increases the instability of the system until the boom – auroral storm.
This can only increase our understanding of the auroral processes of both planets and can help us better understand the aurora of other bodies in the future, including brown dwarfs, which have auroras strong enough to detect them in the future. interstellar space, even when not close to the star.
“While the‘ engine ’of auroras on Earth and Jupiter is very different, showing for the first time the links between the two systems allows us to identify universal phenomena and distinguish them from the particularities relating to each planet,” he said. Yao.
“The Earth’s and Jupiter’s magnetospheres store energy through very different mechanisms, but when this accumulation reaches a breaking point, the two systems release that energy explosively in a surprisingly similar way.”
The research has been published in AGU Advances.