Jupiter's aurora works in unearthly ways

08 September 2017
Posted by Alexandra Ashcroft.

Scientists have rewritten the rules of Jupiter’s auroras to explain the latest data from NASA's Juno Mission.

We’ve all seen images of the Northern lights, or the aurora borealis. Some of us may have even had the privilege of viewing them in person. Breathtaking patterns of different coloured lights snaking across the night’s sky at the earth’s poles.

Some gaze up at this light show and ask how, and why. Others stare even further, inquiring if other planets have their own auroras and, if so, are they the same as Earth’s.

One such curious person is Dr. Barry Mauk, of John Hopkins University Applied Physics Laboratory; the lead investigator of the Jupiter Energetic Particle Detector Instrument (yes, it’s called JEDI) on NASA’s Juno mission, which is currently orbiting Jupiter.

Mauk describes that they’ve seen aurora’s on “Earth, Jupiter, Saturn, Uranus and Neptune so far”. For the latter three planets, they “don’t quite know which ... processes are involved in generating the aurora.”

Mauk explains that Earth’s “aurora is just an image of… very complicated electrical processes that are going [on] above Earth’s atmosphere.” A key player in this processes is Earth’s magnetosphere, or the magnetic field that surrounds our planet. 

On earth, solar winds from the sun hit Earth’s magnetosphere where they get drawn up to the poles. Here they encounter resistance, which ultimately creates Earth’s auroras.

Mauk participated in NASA’s Juno mission “with the one goal of understanding how Jupiter’s aurora is generated” and published the results, this week, in Nature.

When Juno flew JEDI over the auroras it detected “that there are large electrical potentials...that are participating in the generation of Jupiter’s aurora.”

He argues that in order to understand just how these electrical potentials create Jupiter’s auroras, we must first consider a car… well, a car battery to be precise.

“A car battery, at least in the United States, has 12 Volts of electrical potential. If you use that battery to light a light bulb, that battery takes that electrical potential and puts it across the light bulb. That electrical potential drives an electrical current through the light bulb and causes it to light up.”

Mauk reveals that the process in the car “has some similarities to the aurora: there’s an electrical potential that is driving electrons down onto the atmosphere and causing the atmosphere to light up.”

Although larger than expected, the discovery of these electrical potentials was not surprising. Ultimately, auroras on both Earth and Jupiter are caused by electrical potentials interacting with the atmosphere, causing the beautiful light shows.

Yet Mauk found that Earth and Jupiter have different power sources of these electrical potentials.

He says that “the solar wind blows over the magnetic field of earth and acts an electrical generator” and that they expected the power source on Jupiter to be the same.

However, Mauk divulges that “the rotation of Jupiter within its own large magnetic field acts an electrical generator” and this powers the aurora.

But Mauk also discovered that “these electrical potentials, while contributing to Jupiter’s aurora, are not the most important source of Jupiter’s brightest aurora.”

He found this really surprising “because the electrical potentials are thought to be the most important source of the highest intensity aurora at Earth.”

Mauk believes that waves within the gases above the atmosphere might be responsible for fueling the electrical potentials that create Jupiter’s strongest aurora.

Despite these profound differences between Earth and Jupiter, Mauk says that earlier missions suggest that Jupiter’s auroras actually look very similar to our own Northern lights, just bigger.

So if future humans ever find a way to survive on, or around, this mysterious gas giant...the aurora might provide a little reminder of home.

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