Jupiter's internal magnetic field is changing over time, a phenomenon observed by the US National Aeronautics and Space Administration (NASA) for the first time outside of the Earth, the agency has said.

The phenomenon, called secular variation, was detected by NASA's Juno spacecraft orbiting Jupiter, according to a release of the agency's Jet Propulsion Laboratory on Monday.

Juno determined that Jupiter's secular variation is most likely driven by the planet's deep atmospheric winds, the report said.

The winds, believed to shear the magnetic field, extend from the planet's surface to over 1,860 miles (about 3,000 km) deep, where the planet's interior begins changing from gas to highly conductive liquid metal.

The discovery will help scientists further understand Jupiter's interior structure and changes in the Earth's magnetic field.

"Secular variation has been on the wish list of planetary scientists for decades," said Scott Bolton, principal investigator for Juno from the Southwest Research Institute in San Antonio, Texas.

"This discovery could only take place due to Juno's extremely accurate science instruments and the unique nature of Juno's orbit, which carries it low over the planet as it travels from pole to pole," he added.

Scientists compared data from NASA's past missions to Jupiter to a new model of Jupiter's magnetic field collected by Juno, and found "small but distinct changes to the field," the report said.

"Having a baseline of close-up observations over four decades long provided us with just enough data to confirm that Jupiter's magnetic field does indeed change over time," said Kimee Moore, a Juno scientist from Harvard University in Cambridge, Massachusetts.

"With this new understanding of magnetic fields ... we will begin to create a planetwide map of Jupiter's secular variation," said Moore. "It may also have applications for scientists studying (the) Earth's magnetic field, which still contains many mysteries to be solved."

A paper on the discovery was published Monday in the journal Nature Astronomy.