Uranus' magnetosphere - the region defined by the icy 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, scientists have discovered.
The discovery was made based on the data from NASA's Voyager 2 spacecraft that flew closely past Uranus -- the seventh planet from the Sun - more than 30 years ago in January 1986.
The finding showed that magnetosphere is 'open' in one orientation, allowing solar wind to flow into it. It is later "closed", forming a shield against the solar wind and deflecting it away from the planet.
"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," said Carol Paty, Associate Professor at Georgia Institute of Technology.
Reconnection of magnetic fields is a phenomenon throughout the solar system. It is one reason for the Earth's auroras.
Since the same alignment of the Earth's magnetosphere is always facing toward the sun, the magnetic field threaded in the solar wind must change direction in order to reconfigure the Earth's field from closed to open.
Rather than the solar wind dictating a switch like on the 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.For the study, detailed in the Journal of Geophysical Research: Space Physics, the team used numerical models to simulate the planet's global magnetosphere and to predict favourable reconnection locations. The researchers then plugged in data collected by Voyager 2 during its five-day flyby in 1986.
Learning more about Uranus is one key to discovering more about planets beyond our solar system, the researchers noted.