Juno finds changes in Jupiter's magnetic field

NASA's Juno mission to Jupiter has enabled the first definitive detection, beyond our world, of an internal magnetic field that evolves over time, a phenomenon called secular variation. Juno has determined that the secular variation of the gas giant is probably due to the deep atmospheric winds of the planet.

This discovery will help scientists better understand Jupiter's inner structure, including atmospheric dynamics, as well as changes in the Earth's magnetic field. An article on discovery was published today in the journal Nature Astronomy.

"Secular variation has been on the agenda of planetary scientists for decades," said Scott Bolton, Juno's senior investigator at the Southwest Research Institute in San Antonio. "This discovery could only be realized because of Juno's extremely precise scientific instruments and the unique nature of its orbit, which makes it slide over the planet as it unfolds." moves from pole to pole. "

The characterization of the magnetic field of a planet requires close-up measurements. Juno scientists compared data from previous NASA Jupiter missions (Pioneer 10 and 11, Voyager 1 and Ulysses) to a new Jupiter magnetic field model (called JRM09). The new model is based on data collected in the first eight scientific passages of Jupiter using its magnetometer, an instrument capable of generating a detailed three-dimensional map of the magnetic field.

What scientists have discovered is that since the first Jupiter magnetic field data provided by the Pioneer spacecraft to the latest data provided by Juno, the field has undergone minor but distinct modifications.

"Finding something as minute as these changes in something as huge as Jupiter's magnetic field was a challenge," said Kimee Moore, Juno Scientist at Harvard University in Cambridge, in Massachusetts. "Having a database of close-up observations over four decades has provided us with just enough data to confirm that Jupiter's magnetic field is indeed changing over time."

Once the Juno team proved that a secular variation was occurring, it sought to explain how such a change could occur. The operation of Jupiter's atmospheric (or zonal) winds best explained the changes in his magnetic field. These winds extend from the surface of the planet to more than 3,000 km deep, where the interior of the planet begins to pass from gas to a highly conductive liquid metal. They are thought to cut magnetic fields, stretch them and transport them around the planet

The secular variation of Jupiter was nowhere as large as that of the great blue spot of the planet, an area of ​​intense magnetic field near the equator of Jupiter. The combination of the great blue spot, with its powerful localized magnetic fields, and strong zonal winds at this latitude causes the greatest secular variations of the field on the Jovian world.

"It's amazing that a narrow magnetic hot spot, the Great Blue Spot, may be responsible for almost all the secular variation of Jupiter, but the numbers confirm it," Moore said. "With this new understanding of magnetic fields, we will begin to create, in subsequent scientific passages, a detailed map of the secular variation of Jupiter, and may also have applications for scientists studying the Earth's magnetic field, which still contains many mysteries to solve. "