If you were soaring through Jupiter's turbid skies wearing a pair of X-ray goggles, you might get lucky and witness something incredible. Brilliant flashes of light, more luminous and powerful than the Sun, occurring every 26 minutes and stretching as far as the eye can see. That's the essence of a massive solar storm recently witnessed for the first time near Jupiter's north pole. "When I first saw this, I thought I'd made a mistake," Will Dunn, a PhD student studying astrophysics at the University College London, told Gizmodo. The northern lights Dunn observed on Jupiter are hundreds of times brighter than the aurora borealis on Earth. "We're still not sure exactly what's causing it."
Jupiter's northern lights, created when the gas giant's prodigious magnetic field interacts with charged particles from the Sun, have long fascinated planetary scientists. But after decades of observation, many puzzles remain. Chief among Jupiter's space weather mysteries is a bright X-ray aurora, located near the planet's north pole. It never goes away, but since 2006, scientists have watched it brighten and fade every 45 minutes, light a lightbulb on a dimmer switch. Now, Dunn's observations with the Chandra X-ray observatory and other telescopes have added another twist to this dazzling enigma.
Jupiter's x-ray aurora, overlain on a view captured by the Hubble Space Telescope. Image Credit: Joseph DePasquale, Smithsonian Astrophysical Observatory/Chandra X-ray Center
Writing today in the Journal of Geophysical Research, Dunn and his co-authors describe what happened when a coronal mass ejection — a giant cloud of magnetized plasma that erupted from the surface of the Sun — struck the gas giant's magnetosphere in 2011. When this happens on Earth, we get the northern lights. On Jupiter, the forever-aurora gets bigger and flashier.
"We saw the pulsing get much quicker: it happens about every 26 minutes during a solar storm," Dunn said. "And we saw a bright enhancement in a region where we'd never seen it before."
"If your eyes could see X-rays, you'd see something similar to the aurora on Earth," Dunn continued. "Except the flashing across the the sky would be much bigger and brighter. Jupiter's auroras cover a region larger than the entire Earth, so it would stretch as far as the eye can see."
Why Jupiter's northern lights flicker to a particular tempo, and why that flickering accelerated during the 2011 solar storm, are questions that planetary scientists would love to answer. "We think that when a coronal mass ejection crashes into Jupiter's magnetosphere, it compresses it by about two million kilometres," Dunn said. But for more details, we may have to wait for NASA's Juno mission, which reaches the boundary between the Jupiter's magnetic field and the solar wind this winter.
In addition to offering yet another mind-blowing glimpse into the meteorological events occurring in our cosmic backyard, Jupiter's aurora provides a second benchmark for understanding how magnetic fields protect planets from powerful stellar eruptions. And that knowledge may eventually aid in the search for life beyond our solar system.
"We have a pretty good understanding of how the Earth's magnetosphere works," Dunn said. "But the universe is filled with magnetically active objects, including billions of exoplanets. Understanding the diversity of magnetic fields has relevance for understanding whether any of those other planets can support life."
Top: Artist's concept of Jupiter's magnetosphere interacting with the solar wind. Image Credit: JAXA