Jupiter's Auroras Present a Powerful Mystery

Scientists on NASA's Juno mission have observed massive amounts of energy swirling over Jupiter's polar regions that contribute to the giant planet's powerful auroras - only not in ways the researchers expected.

This is a reconstructed view of Jupiter's northern lights through the filters of Juno's Ultraviolet Imaging Spectrometer (UVS) instrument. Image Credit: NASA/JPL-Caltech/Bertrand Bonfond

Examining data collected by the ultraviolet spectrograph and energetic-particle detector instruments aboard the Jupiter-orbiting Juno spacecraft, a team led by Barry Mauk of the Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, observed signatures of powerful electric potentials, aligned with Jupiter's magnetic field, that accelerate electrons toward the Jovian atmosphere at energies up to 400,000 electron volts.

This is 10 to 30 times higher than the largest auroral potentials observed at Earth, where only several thousands of volts are typically needed to generate the most intense auroras -- known as discrete auroras -- the dazzling, twisting, snake-like northern and southern lights seen in places like Alaska and Canada, northern Europe, and many other northern and southern polar regions.

Jupiter has the most powerful auroras in the solar system, so the team was not surprised that electric potentials play a role in their generation. What's puzzling the researchers is that despite the magnitudes of these potentials at Jupiter, they are observed only sometimes and are not the source of the most intense auroras, as they are at Earth.

Scientists consider Jupiter to be a physics lab of sorts for worlds beyond our solar system, saying the ability of Jupiter to accelerate charged particles to immense energies has implications for how more distant astrophysical systems accelerate particles. But what they learn about the forces driving Jupiter's auroras and shaping its space weather environment also has practical implications in our own planetary backyard.

"The highest energies that we are observing within Jupiter's auroral regions are formidable. These energetic particles that create the auroras are part of the story in understanding Jupiter's radiation belts, which pose such a challenge to Juno and to upcoming spacecraft missions to Jupiter under development," said Mauk. (NASA)

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