The magnetic field of Uranus flips on and off just like a light switch every day as the planet rotates, scientists have discovered. Researchers from Georgia Institute of Technology in the US found this after studying the data provided by NASA’s Voyager 2 spacecraft. In 1986, the Voyager 2 spacecraft had sped past Uranus.
"The magnetosphere is 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," researchers said.
On the other hand, the Earth’s magnetosphere only switches between open and closed when there are changes in the solar wind.
The magnetic field threaded in the ever-present solar wind must change direction to reconfigure Earths field from closed to open as the same alignment of Earth’s magnetosphere always faces toward the sun. This frequently happens with strong solar storms.
Uranus lies and rotates on its side, and its magnetic field is lopsided – it’s off-centred and tilted 60 degrees from its axis.
The magnetic field tumbles asymmetrically relative to the solar wind direction as the icy giant completes its 17.24-hour full rotation. This is because of those features.
Rather than the solar wind dictating a switch like here on Earth, 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, researchers said.
"Uranus is a geometric nightmare. The magnetic field tumbles very fast, like a child cartwheeling down a hill head over heels," said Carol Paty associate professor at Georgia Institute of Technology.
"When the magnetised 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," she added.
Reconnection of magnetic fields is a phenomenon throughout the solar system. It is one reason for Earths auroras. Researchers used numerical models to simulate the planets global magnetosphere and to predict favourable reconnection locations.
They plugged in data collected by Voyager 2 during its five-day flyby in 1986. Its the only time a spacecraft has visited.
"Perhaps what we see on Uranus and Neptune is the norm for planets: very unique magnetospheres and less-aligned magnetic fields," said Xin Cao from Georgia Institute of Technology.
"Understanding how these complex magnetospheres shield exoplanets from stellar radiation is of key importance for studying the habitability of these newly discovered worlds," Cao added.
The study was published in the Journal of Geophysical Research.
(With inputs from PTI)