Unusual rotation causes Uranus’ light switch effect

Uranus Magnetosphere

Scientists have discovered what they call a light switch effect on Uranus and the reason behind this effect is the planet’s magnetosphere – region defined by the icy planet’s magnetic field and the material trapped inside it.

Data from NASA’s Voyager 2 spacecraft that flew past Uranus more than three decades ago helped scientists discover the peculiar effect. According to scientists at Georgia Institute of Technology the magnetosphere gets flipped on and off like a light switch every day as it rotates along with the planet.

Scientists explain that the data indicates an opening in the magnetosphere in one orientation through which the solar wind flows into it. Then there is the “closed” bit that forms a shield deflecting the solar wind 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.


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