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Magnetic Field Around Uranus Are a Chaotic Mess

Using data from the Voyager 2 mission, researchers have modeled Uranus’s off-kilter magnetosphere

Auroras on Uranus caused by changes in its magnetosphere (NASA/JPL )
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Uranus is one of our weirder neighbors. First things first: It spins on its side. Unlike other planets, which spin on an axis that is more or less in the same plane as their orbit, icy Uranus is tipped sideways, spinning at a roughly 98-degree angle to its orbit around the sun. Its magnetosphere also spins a bit off-kilter, and as Leah Crane reports for New Scientist reports, a new models suggest that this tilted spin causes this protective shield to open up and close every day.

To figure out how the process works on Uranus, researchers from the Georgia Institute of Technology examined data collected over 30 years ago by Voyager 2, the last probe to collect data from the icy planet. They then created a model of the planet’s magnetosphere to study its chaotic orbit. They published their results in The Journal of Geophysical Research: Space Physics.

The magnetic fields for most of the planets in our Solar System are pretty orderly, Crane writes. For instance, the magnetic field lines on Earth emerge near the north and south poles and wrap around the globe in a type of bubble of magnetism, known as the magnetosphere, which spins along with our planet. 

Most of the time, this little bubble protects us from solar winds of charged particles emitted from the sun. This is called the "closed" position for the magnetosphere, in which the magnetic field lines run in the same direction as the sun’s.

On occasion, however, when a solar storm is strong enough, it can cause the Earth and the sun’s magnetic field lines to cross, creating what's known as a "magnetic reconnection," which releases stored energy and ejects charged particles toward Earth (we see these as auroras). This is considered an “open” position.

But for Uranus, the magnetosphere tilts 60 degrees off its axis. That means every day during its 17.24-hour rotation, Uranus’ magnetic field opens and closes to the solar wind. “As it is tumbling around, the magnetosphere’s orientation is changing in all sorts of directions,” Carol Paty, researcher the Georgia Institute of Technology in Atlanta and co-author of the study, tells Crane.

It's a "geometric nightmare," she explains in the press release. “The magnetic field tumbles very fast, like a child cart wheeling down a hill head over heels. When the magnetized solar wind meets this tumbling field in the right way, it can reconnect and Uranus’ magnetosphere goes from open to closed to open on a daily basis.”

Though it may seem like just a wacky cousin, icy planets like Uranus and Neptune may be pretty standard throughout in the universe. In fact, a recent study suggests that “mini-Neptunes,” are one of the most common types of planets found outside our Solar System so far.

“We have the Kepler telescope, which is revealing thousands of planets throughout the galaxy,” Paty tells Rae Paoletta at Gizmodo. “It turns out statistically, the largest proportion of these exoplanets are most similar in size—and likely dynamic—in structure to Uranus and Neptune. They might provide a bit of a benchmark for understanding dynamics at all of these exoplanets.”

Hopefully we’ll be getting more information on Uranus and its quirks in the decades to come. Just last week a study group at NASA released a proposal outlining missions to study Uranus and Neptune to examine their composition, atmosphere and magnetic fields. The best launch date for a mission to Uranus would be 2034, and it would take about 14 years for a probe to reach the planet. Prime time for a Neptune launch doesn’t occur until 2041 or later.

About Jason Daley

Jason Daley is a Madison, Wisconsin-based writer specializing in natural history, science, travel, and the environment. His work has appeared in Discover, Popular Science, Outside, Men’s Journal, and other magazines.

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