More than 30 years after Voyager 2 sped past Uranus, Georgia Institute of Technology researchers are using the spacecraft's data to learn more about the icy planet. Their new study suggests that Uranus' magnetosphere, the region defined by the planet's magnetic field and the material trapped inside it, gets flipped on and off like a light switch every day as it rotates along with the planet. It's "open" in one orientation, allowing solar wind to flow into the magnetosphere; it later closes, forming a shield against the solar wind and deflecting it away from the planet.

This is much different from Earth's magnetosphere, which typically only switches between open and closed in response to changes in the solar wind. Earth's magnetic field is nearly aligned with its spin axis, causing the entire magnetosphere to spin like a top along with Earth's rotation. Since the same alignment of Earth's magnetosphere is always facing toward the sun, the magnetic field threaded in the ever-present solar wind must change direction in order to reconfigure Earth's field from closed to open. This frequently occurs with strong solar storms.

But Uranus lies and rotates on its side, and its magnetic field is lopsided -- it's off-centered and tilted 60 degrees from its axis. Those features cause the magnetic field to tumble asymmetrically relative to the solar wind direction as the icy giant completes its 17.24-hour full rotation.

Rather than the solar wind dictating a switch like here on Earth, the researchers say Uranus' rapid rotational change in field strength and orientation lead to a periodic open-close-open-close scenario as it tumbles through the solar wind.

"Uranus is a geometric nightmare," said Carol Paty, the Georgia Tech associate professor who co-authored the study. "The magnetic field tumbles very fast, like a child cartwheeling 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."

Paty says this solar wind reconnection is predicted to occur upstream of Uranus' magnetosphere over a range of latitudes, with magnetic flux closing in various parts of the planet's twisted magnetotail.

Reconnection of magnetic fields is a phenomenon throughout the solar system. It occurs when the direction of the interplanetary magnetic field -- which comes from the sun and is also known as the heliospheric magnetic field -- is opposite a planet's magnetospheric alignment. Magnetic field lines are then spliced together and rearrange the local magnetic topology, allowing a surge of solar energy to enter the system.

Magnetic reconnection is one reason for Earth's auroras. Auroras could be possible at a range of latitudes on Uranus due to its off-kilter magnetic field, but the aurora is difficult to observe because the planet is nearly 2 billion miles from Earth. The Hubble Space Telescope occasionally gets a faint view, but it can't directly measure Uranus' magnetosphere.

The Georgia Tech researchers used numerical models to simulate the planet's global magnetosphere and to predict favorable reconnection locations. They plugged in data collected by Voyager 2 during its five-day flyby in 1986. It's the only time a spacecraft has visited.

The researchers say learning more about Uranus is one key to discovering more about planets beyond our solar system.

"The majority of exoplanets that have been discovered appear to also be ice giants in size," said Xin Cao, the Georgia Tech Ph.D. candidate in earth and atmospheric sciences who led the study. "Perhaps what we see on Uranus and Neptune is the norm for planets: very unique magnetospheres and less-aligned magnetic fields. Understanding how these complex magnetospheres shield exoplanets from stellar radiation is of key importance for studying the habitability of these newly discovered worlds."

Xin Cao, Carol Paty. Diurnal and Seasonal Variability of Uranus’ Magnetosphere. Journal of Geophysical Research: Space Physics, 2017; DOI: 10.1002/2017JA024063

My anus do what now?

So instead of releasing wind, Uranus catches wind from others? Interesting.

This I did not understand.

All I know is my anus opens and closes to wind many times a day.

There was a resurgence in amateur astronomy around the time of the return of Halley's Comet (1986).
Astronomers wanted to avoid the juvenile humor associated with the name Uranus and considered renaming the planet.
The preferred new name would have been Urectum.

I've never heard it called a magnetosphere before, but the next time I am tempted to yell at a bad driver, I will just refer to them as a magnetosphere.



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quote:

Originally posted by arfmel:
My anus do what now?

Opens and closes based on the wind's direction.

quote:

Uranus' magnetosphere opens and closes to solar wind

Well, mine certainly doesn't... do whatever that is.

quote:

Uranus' magnetosphere opens and closes to solar wind

Blatantly incorrect. It's lunar wind.

quote:

"Uranus is a geometric nightmare," said Carol Paty,

Well ,that made me pucker up.

Haha, thus far, the comments are as expected...

quote:

Originally posted by gearhounds:
Haha, thus far, the comments are as expected...

We can't help ourselves.

Seriously though, it may be that we are on the edge of a new level of understanding of the perfect balance of our universe. I have a feeling this timed on/off switch plays a role in the health of our solar system, and our planet.



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I'm sure there's a joke in here somewhere, now if I could only find it...

So we can't colonize Uranus... Why would we want to inhabit an ice planet, anyway?

quote:

Originally posted by ArtieS:
I'm sure there's a joke in here somewhere, now if I could only find it...

Ah, blow it out uranus!!

No one's going to Uranus anytime soon.

quote:

Originally posted by Orguss:
So we can't colonize Uranus... Why would we want to inhabit an ice planet, anyway?

We could hold the winter olympics there

quote:

Originally posted by Orguss:
So we can't colonize Uranus... Why would we want to inhabit an ice planet, anyway?

To make the largest pitcher of martinis in the Universe, maybe?

tac

quote:

Originally posted by ArtieS:
I'm sure there's a joke in here somewhere, now if I could only find it...

Use both hands...