Mystery of Jupiter’s aurora grows

Jupiter's most powerful aurorae are not accompanied by a strong electric potential field as they are on Earth. These are the findings of a study using data captured by NASA's Juno spacecraft, and only serve to deepen the mystery of the Gas Giant's aurora.

A reconstructed view of Jupiter's northern lights through the filters of the Juno Ultraviolet Imaging Spectrograph instrument on Dec. 11, 2016. Credit: NASA/JPL-Caltech/Bertrand Bonfond
Published: September 7, 2017 at 12:00 pm
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The mystery of Jupiter’s aurora has only grown after recent observations taken by NASA’s Juno spacecraft. The Gas Giant has the most powerful aurorae in the Solar System, but scientists cannot be certain exactly what drives them.


The Juno mission has confused this matter even more as observations of Jupiter reveal that strong electric potential fields, the mechanism that produces the most intense terrestrial aurora, is only present for some of Jupiter’s powerful displays.

Aurorae are created when charged particles from the Sun, mostly electrons and protons, become caught in a planet’s magnetosphere.

This accelerates the particles to high energies, then smashes them into the atmosphere causing the gases there to glow.

On Earth, the most intense of these aurorae are accompanied by a strong electric potential field and it was expected that Jupiter’s would have a similar field.

Though Juno measured an electric potential that could reach up to 30 times higher than the largest potentials seen around Earth, they were not always present when Jupiter put on its most spectacular light shows.

“At Jupiter, the brightest aurorae are caused by some kind of turbulent acceleration process that we do not understand very well,” says Barry Mauk from Johns Hopkins University, who led the team behind the study.

"There are hints in our latest data indicating that as the power density of the auroral generation becomes stronger and stronger, the process becomes unstable and a new acceleration process takes over. But we’ll have to keep looking at the data.”

Jupiter and its aurora offer an excellent window into the planet’s magnetosphere, creating a planetary laboratory where scientists can examine how particles are accelerated to high energies.

This knowledge can then be applied not just to other planets but to other astrophysical objects that accelerate particles to incredible speeds.

It is also important to know about how these particles behave near planets, as they create formidable radiation belts that may cause difficulties for future space missions.

“Engineering around the debilitating effects of radiation has always been a challenge to spacecraft engineers for missions at Earth and elsewhere in the Solar System," says Mauk.


"What we learn here, and from spacecraft like NASA’s Van Allen Probes and Magnetospheric Multiscale mission (MMS) that are exploring Earth’s magnetosphere, will teach us a lot about space weather and protecting spacecraft and astronauts in harsh space environments."


Ezzy Pearson is the News Editor of BBC Sky at Night Magazine. Her first book about the history of robotic planetary landers is out now from The History Press.


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