Flowy curtains of aurora lights are observed on Earth when solar ejections collide with our magnetic field. This generates currents of charged particles that flow into the north or south poles, creating dazzling displays when they hit oxygen and nitrogen. Saturn has aurora lights too, and newly released Hubble images capturing the dancing auroral lights at the gas giant’s north pole suggest they result from the collapse of the planet’s magnetic tail.
Saturn’s magnetosphere -- the big magnetic bubble that surrounds the planet -- is compressed on the side facing the sun, and it streams out into a long “magnetotail” on the planet’s nightside. Just like with comets, the magnetotails of Earth and Saturn are made of electrified gas from the sun.
Now it appears that when strong bursts of particles from the sun hit Saturn, the magnetotail collapses and then reconfigures itself -- a disturbance of the magnetic field that’s reflected in the dynamics of auroras. “We have always suspected this was what also happens on Saturn,” Jonathan Nichols of the University of Leicester says in a statement. “This evidence really strengthens the argument.”
The ultraviolet images were taken by Hubble’s Advanced Camera for Surveys during April and May of last year from the space telescope’s perspective in orbit around Earth. The images are able to provide the first detailed look at dynamics in the “choreography” of auroral glow because Hubble captured them right at that very moment when Saturn’s magnetic field is blasted by particles streaming from the sun.
Hubble managed to capture a particularly dynamic light show: Some bursts of light shooting around the polar regions traveled at least three times faster than the speed of Saturn’s rotation. (The planet has a 10-hour rotation period.)
“We can see that the magnetotail is undergoing huge turmoil and reconfiguration, caused by buffering from solar wind,” Nichols explains. “It’s the smoking gun that shows us that the tail is collapsing.”
Their findings were published in the American Geophysical Union’s Geophysical Research Letters this month.
Image: NASA/ESA, Acknowledgement J. Nichols (University of Leicester)