NASA’s Juno reveals the dark origins of one of Jupiter’s great light shows

New results from the Ultraviolet Spectrograph instrument on NASA’s Juno mission reveal for the first time the birth of morning auroral storms – the early morning that becomes unique to Jupiter’s spectacular aurorae. These immense transient light displays take place at both Jupiter’s poles and had previously only been seen by ground and orbiting observatories, most notably NASA’s Hubble Space Telescope. The results of this study were published March 16 in the journal AGU advances

First discovered by Hubble’s Faint Object Camera in 1994, morning storms consist of momentary but intense clearing and widening of Jupiter’s main auroral oval – an elongated curtain of light that surrounds both poles – near where the atmosphere emerges from the darkness in the early morning region. to appear. . Before Juno, observations of Jupiter’s ultraviolet aurora provided only side views, hiding everything that happened on the planet’s night side.

“By observing Jupiter’s aurora from Earth, you cannot see beyond the limb, to the night side of Jupiter’s poles. Explorations with other spacecraft – Voyager, Galileo, Cassini – took place from relatively long distances and did not fly. across the poles, so they couldn’t see the full picture, “said Bertrand Bonfond, a researcher from the University of Liège in Belgium and lead author of the study.” That’s why Juno’s data is a real game changer, helping us better understand what’s going on. happens on the night side, where the dawn storms are born. “

Researchers found that morning storms are born on the night side of the gas giant. As the planet rotates, the approaching morning storm rotates with it towards the daytime, where these complex and intensely bright aurora elements become even brighter, sending hundreds to thousands of gigawatts of ultraviolet light into space everywhere. The jump in brightness implies that morning storms are dumping at least 10 times more energy into Jupiter’s upper atmosphere than typical auroras.

“When we looked at the whole series of morning storms, we couldn’t help but notice that they are very similar to some kind of terrestrial auroras called substorms,” ​​said Zhonghua Yao, co-author of the study at the University of Liège. “

Substorms are the result of momentary perturbations in the Earth’s magnetosphere – the region of space controlled by the planet’s magnetic field – that release energy high in the planet’s ionosphere. The similarity between terrestrial and Jovian substorms is surprising because the magnetospheres of Jupiter and Earth are radically different. On Earth, the magnetosphere is essentially controlled by the interaction of the solar wind – the stream of charged particles flowing from the sun – with the Earth’s magnetic field. Jupiter’s magnetosphere is populated primarily by particles escaping from the volcanic moon Io, which then become ionized and trapped around the gas giant through its magnetic field.

These new findings will allow scientists to further study the differences and similarities that drive the formation of aurora, giving them a better understanding of how these most beautiful planetary phenomena occur on worlds both within our solar system and beyond.

“The power that Jupiter possesses is astonishing. The energy in this dawn aurorae is yet another example of how powerful this gigantic planet really is,” said Scott Bolton, Juno principal investigator of the Southwest Research Institute in San Antonio. “The dawn storm revelations are another surprise from the Juno mission, which is constantly rewriting the book about the work of the giant planet. With NASA’s recent mission expansion, we look forward to many more new insights and discoveries.”