Uranus's Magnetic Field Switches Open and Closed on a Daily Basis

Uranus has a strange magnetic field. On the left Uranus appears as it would to the naked eye; on the right is a false-color picture revealing a dark polar hood surrounded by a series of progressively lighter concentric bands. NASA

Uranus is a strange place. Among many of its quirks is that it has the most unusual magnetic field in the solar system. Unlike Earth and many other planets, this field is not closely aligned with its rotational axis—it's tilted by 60 degrees. Added to this is the fact that Uranus rotates on its side as it circles the sun.

This strange arrangement causes Uranus's magnetic field, also known as its magnetosphere, to flip open and closed on a daily basis, new research suggests. When closed, it acts like an umbrella to deflect solar wind, the continual stream of charged particles produced by the sun that perpetually bombard Uranus and other planets. But when it's open, these energized particles rush in and get trapped there.

To help picture the arrangement, Georgia Institute of Technology professor Carol Paty suggests visualizing a child cartwheeling toward you—you'd see hands, then feet, then hands again, over and over. The hands represent an open magnetosphere, while the feet represents a closed orientation. And it keeps going like this, toggling back and forth about once every Uranian day, which lasts over 17 (earthly) hours.

This gif shows Uranus' magnetosphere switching between open and closed configurations. Georgia Tech

On Earth, solar wind do sometimes breach the magnetosphere, and this is what causes auroras, the fabulous displays known as the Southern and Northern Lights. But on our planet the magnetic field is only about 10 degrees tilted away from its spin axis, meaning there is no such chaos as what Uranus experiences.

Paty and her student Xin Cao authored a study describing Uranus' magnetosphere, drawing on data collected by the Voyager 2 spacecraft way back in 1986 as it passed by the ice giant. Although its magnetics have fascinated scientists for decades, nobody had yet worked out the mechanics of its rotation in quite this way before, Paty says.

The paper was published in the Journal of Geophysical Research: Space Physics, shortly after NASA released a report proposing four different types of missions that could reach Uranus and Neptune within the next decade or so.

Though Uranus does seem odd, at least for our solar system, many of the exoplanets so far discovered appear to be about the same size as Uranus and Neptune, and may also be ice giants, Paty says.

As far as Uranus puns, which invariable surface when the planet is discussed, Paty says that "Uranus is such a fascinating planet—if the... puns make people more interested in it, than it's okay." Pause. "But it does make me a little sad."

Studies of Uranus may help better understand Earth's magnetic field. "Looking at how Uranus's complicated, strange magnetosphere works helps us understand how all the other systems work," George Hospodarsky at the University of Iowa tells New Scientist. "It's sort of like doing an experiment one way and then turning it upside down and starting again. If it still works, your theories are good."

Cao and Paty / Journal of Geophysical Research: Space Physics