What's the mystery behind Jupiter's powerful auroras? Juno gives an unexpected answer

Reconstructed view of Jupiter’s northern lights through the filters of the Juno Ultraviolet Imaging Spectrograph instrument (Image courtesy: NASA/JPL-Caltech/Bertrand Bonfond)

New Delhi: Being the largest – and now officially the oldest – planet of the solar system, Jupiter has caught the fancy of scientists and astronomers, compelling them to study the gas giant better by delving into its interiors.

The Juno spacecraft was, therefore, developed to help scientists in this endeavour. Juno's entry into Jupiter's orbit in July 2016, prepared the ground for amazing revelations and information to be disclosed and the spacecraft has been highly successful and efficient in providing all that and more.

Scientists at NASA have often observed that Jupiter has the most powerful auroras in the solar system and Juno has just provided fodder for their pulsating energy, but not in the way scientists expected.

It has been observed that massive amounts of energy swirl over Jupiter’s polar regions that contribute to the giant planet’s powerful auroras, but what's the mystery?

According to NASA, 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.

The team was not surprised that electric potentials play a role in their generation. What’s puzzling the researchers, Mauk said, 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.

“At Jupiter, the brightest auroras are caused by some kind of turbulent acceleration process that we do not understand very well,” said Mauk, who leads the investigation team for the APL-built Jupiter Energetic Particle Detector Instrument (JEDI). “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.”

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, NASA reported.