Auroral shows proceed to intrigue scientists, whether or not the brilliant lights shine over Earth or over one other planet. The lights maintain clues to the make-up of a planet’s magnetic subject and the way that subject operates.
New analysis about Jupiter proves that time — and provides to the intrigue.
Peter Delamere, a professor of house physics on the University of Alaska Fairbanks Geophysical Institute, is amongst a global staff of 13 researchers who’ve made a key discovery associated to the aurora of our photo voltaic system’s largest planet.
The staff’s work was revealed April 9, 2021, within the journal Science Advances. The analysis paper, titled “How Jupiter’s unusual magnetospheric topology structures its aurora,” was written by Binzheng Zhang of the Department of Earth Sciences on the University of Hong Kong; Delamere is the first co-author.
Research carried out with a newly developed world magnetohydrodynamic mannequin of Jupiter’s magnetosphere gives proof in help of a beforehand controversial and criticized concept that Delamere and researcher Fran Bagenal of the University of Colorado at Boulder put ahead in a 2010 paper — that Jupiter’s polar cap is threaded partially with closed magnetic subject traces fairly than solely with open magnetic subject traces, as is the case with most different planets in our photo voltaic system.
“We as a community tend to polarize — either open or closed — and couldn’t imagine a solution where it was a little of both,” mentioned Delamere, who has been learning Jupiter since 2000. “Yet in hindsight, that is exactly what the aurora was revealing to us.”
Open traces are people who emanate from a planet however path off into house away from the solar as an alternative of reconnecting with a corresponding location within the reverse hemisphere.
On Earth, for instance, the aurora seems on closed subject traces round an space known as the auroral oval. It’s the excessive latitude ring close to — however not at — every finish of Earth’s magnetic axis.
Within that ring on Earth, nonetheless, and as with another planets in our photo voltaic system, is an empty spot known as the polar cap. It’s a spot the place magnetic subject traces stream out unconnected — and the place the aurorae hardly ever seem due to it. Think of it like an incomplete electrical circuit in your house: No full circuit, no lights.
Jupiter, nonetheless, has a polar cap during which the aurora dazzles. That puzzled scientists.
The downside, Delamere mentioned, is that researchers have been so Earth-centric of their interested by Jupiter due to what that they had discovered about Earth’s personal magnetic fields.
The arrival at Jupiter of NASA’s Juno spacecraft in July 2016 offered photos of the polar cap and aurora. But these photos, together with some captured by the Hubble Space Telescope, could not resolve the disagreement amongst scientists about open traces versus closed traces.
So Delamere and the remainder of the analysis staff used laptop modeling for assist. Their analysis revealed a largely closed polar area with a small crescent-shaped space of open flux, accounting for under about 9 p.c of the polar cap area. The relaxation was energetic with aurora, signifying closed magnetic subject traces.
Jupiter, it seems, possesses a mixture of open and closed traces in its polar caps.
“There was no model or no understanding to explain how you could have a crescent of open flux like this simulation is producing,” he mentioned. “It just never even entered my mind. I don’t think anybody in the community could have imagined this solution. Yet this simulation has produced it.”
“To me, this is a major paradigm shift for the way that we understand magnetospheres.”
What else does this reveal? More work for researchers.
“It raises many questions about how the solar wind interacts with Jupiter’s magnetosphere and influences the dynamics,” Delamere mentioned.
Jupiter’s aurorally energetic polar cap might, for instance, be as a result of rapidity of the planet’s rotation — as soon as each 10 hours in comparison with Earth’s as soon as each 24 hours — and the enormity of its magnetosphere. Both cut back the impression of the photo voltaic wind, that means the polar cap magnetic subject traces are much less prone to be torn aside to change into open traces.
And to what extent does Jupiter’s moon Io have an effect on the magnetic traces inside Jupiter’s polar cap? Io is electrodynamically linked to Jupiter, one thing distinctive in our photo voltaic system, and as such is continually stripped of heavy ions by its dad or mum planet.
As the paper notes, “The jury is still out on the magnetic structure of Jupiter’s magnetosphere and what exactly its aurora is telling us about its topology.”