Dazzling Auroras on Jupiter? New Study Tries to Explain Phenomenon

Aurora displays remain intriguing to scientists, whether on Earth or in other planets. This is because the bright lights hold the secret to the composition of a planet's magnetic field and how this field works.

New studies on Jupiter show that assertion and adds more to the mystery.

Published in the Science Advances journal, titled "How Jupiter's unusual magnetospheric topology structures its aurora," the research completed with a newly developed global magnetohydrodynamic model of the magnetosphere of Jupiter proves a previously questioned idea on the planet's polar cap. These previous studies assert that Jupiter's polar cap is threaded in part with closed magnetic field lines and not entirely open magnetic field lines, similar to other planets in the solar 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. Yet in hindsight, that is exactly what the aurora was revealing to us." Peter Delamere, a professor of space physics at the University of Alaska Fairbanks Geophysical Institute, said in the study's findings. Delamere, who has been closely studying Jupiter since 2000, is among the 13 researchers behind the significant discovery of auroras on Jupiter.

Key Findings on Auroral Presence on Jupiter's Polar Caps

Open magnetic field lines emanate from a planet but sets off to space away from the Sun and not reattaching with a corresponding position in the opposite hemisphere.

On Earth, the aurora shows on closed field lines circling an area called the auroral oval. It is the high-latitude ring located near the end of each of Earth's magnetic axes.

In that ring, just like in other planets in the solar system, there is an empty spot called the polar cap, where magnetic field lines spread out and aurorae rarely appear due to the phenomenon. It's similar to an incomplete electrical circuit in your home. Without a complete circuit, you would have no lights.

However, Jupiter has a polar cap wherein the aurora still astonishes. And this baffles scientists.

When NASA's Juno spacecraft arrived at Jupiter, it returned images of the planet's polar cap and aurora. But these images and those taken by NASA's Hubble Space Telescope could not settle the dispute among scientists on open lines against closed lines.

Researchers would then turn to computer modeling for assistance. Their findings showed a largely closed polar region with an open flux area that is of a small-crescent shape consisting of nine percent of the polar cap region. The remaining area was active with aurora, showing closed magnetic field lines.

Thus they observed Jupiter as having a combination of open and closed lines in its polar caps.

More Questions Raised on Jupiter's 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; 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," Delamere said.

He added, "To me, this is a major paradigm shift for the way that we understand magnetospheres."

This, however, connote more work for the researchers.

Many questions still remain on Jupiter's polar caps. "It raises many questions about how the solar wind interacts with Jupiter's magnetosphere and influences the dynamics," Delamere said.

The aurorally active polar cap could be due to the speed of the planet's rotation once every 10 hours, compared to the Earth's once every 24 hours, and the size of Jupiter's magnetosphere. Both decrease the solar wind's impact, thus causing the polar cap magnetic field lines to be shredded to become open lines.

Research also needs to be focused on Jupiter's moon and its effect on the magnetic lines within the planet's solar cap? The moon Io is electrodynamically connected to Jupiter, which is distinct in the solar system. This leads to a constant stripping of heavy ions by Jupiter.

Check out more news and information on Auroras on Science Times.