New research reveals secret for Jupiter’s curious aurora activity

Auroral displays continue to intrigue scientists, whether the bright lights are shining over the earth or over another planet. The lights contain clues for the composition of the magnetic field of a planet and how the field works.

New research on Jupiter proves this – and contributes to the plot.

Peter Delamere, a professor of space physics at the University of Alaska Fairbanks Geophysical Institute, is among an international team of 13 researchers who made an important discovery related to the aurora of the largest planet in our solar system.

The team’s work was published in the journal on 9 April 2021 Scientific progress. The research article, entitled “How Jupiter’s unusual magnetospheric topology structures its aurora”, was written by Binzheng Zhang of the Department of Earth Sciences at the University of Hong Kong; Delamere is the primary co-author.

Research conducted with a newly developed global magnetohydrodynamic model of Jupiter’s magnetosphere provides evidence to support a previously controversial and criticized idea put forward by Delamere and researcher Fran Bagenal of the University of Colorado at Boulder in a 2010 article – that Jupiter’s polar cap was thrown in. part with closed magnetic field lines rather than completely with open magnetic field lines, as is the case with most other planets in our solar system.

“We as a community tend to polarize – open or closed – and could not imagine a solution where it was a bit of both,” said Delamere, who has been studying Jupiter since 2000. ‘the aurora was revealed to us. ‘

Open lines are those that originate from a planet but away from the sun in space instead of reconnecting with a corresponding place in the opposite hemisphere.

On Earth, for example, the aurora appears on closed field lines around an area called the auroral oval. It is the ring with a high latitude near – but not at – each end of the Earth’s magnetic axis.

Within the ring on Earth, however, as with other planets in our solar system, there is an empty space called the polar cap. This is a place where magnetic field lines flow out uncoupled – and where the aurorae rarely appear for it. Think of it as an incomplete electrical circuit in your home: no complete circuit, no lights.

Jupiter, however, has a polar cap in which the aurora is blinded. This surprised scientists.

The problem, Delamere said, is that scientists were so earth-centered in their thinking about Jupiter because of what they learned about the Earth’s own magnetic fields.

The arrival at Jupiter of NASA’s spacecraft Juno in July 2016 produced images of the polar cap and the aurora. But these images, along with some captured by the Hubble Space Telescope, could not resolve the differences of opinion between scientists over open lines versus closed lines.

Therefore, Delamere and the rest of the research team used computer modeling to provide assistance. Their research revealed a largely closed polar region with a small crescent-shaped area with open flooding, which covers only about 9 percent of the polar cap region. The rest were active with aurora, meaning closed magnetic field lines.

Jupiter appears to possess a mixture of open and closed lines in its polar caps.

“There was no model or understanding to explain how you can have a sickle of open flood like this simulation delivers,” he said. “It never even occurred to me. I don’t think anyone in the community would have thought of this solution. Yet this simulation yielded it.”

“For me, it’s a big paradigm shift for the way we understand magnetospheres.”

What else does it reveal? More work for researchers.

“This raises a lot of questions about how the solar wind interacts with Jupiter’s magnetosphere and affects the dynamics,” Delamere said.

Jupiter’s northern active polar cap, for example, may be due to the planet’s rapid rotation – once every 10 hours compared to Earth once every 24 hours – and the magnitude of the magnetosphere. Both reduce the impact of the solar wind, which means that the magnetic field lines of the polar cap are less likely to become open lines.

And to what extent does Jupiter’s moon Io affect the magnetic lines within Jupiter’s polar cap? Io is electrodynamically linked to Jupiter, something unique in our solar system, and is constantly being stripped of heavy ions by its parent planet.

As noted in the paper, “The jury is still searching for the magnetic structure of Jupiter’s magnetosphere and what the aurora tells us exactly about its topology.”