"The Great Blue Spot of Jupiter" – "Incredible! Impacts all its magnetic field"

Posted on May 20, 2019

"It's amazing that a narrow magnetic hot spot, the Great Blue Spot, is responsible for almost all the variation of Jupiter, but the numbers confirm it," said Kimee Moore, of Harvard, about the first detection beyond NASA's Juno mission 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. The secular variation of Jupiter was nowhere as great as that of the great blue spot of the planet, a zone 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.

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.

The immobility below is taken from an animation illustrating the magnetic field of Jupiter at a given moment. The large blue spot, concentration of the magnetic field close to the equator and invisible to the eye, stands out particularly. (NASA / JPL-Caltech / Harvard / Moore et al.

"Centennial variation has been on planetary scientists' wish list for decades," said Scott Bolton, senior researcher at Juno's Southwest Research Institute in San Antonio. "This discovery was only made possible by Juno's extremely precise scientific instruments and the unique nature of its orbit, which drives it to the edge of the planet as it 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 during Juno's first eight scientific passes by Jupiter using his magnetometer, an instrument capable of generating a detailed three-dimensional map of the magnetic field.

This striking view of Jupiter's large red stain and turbulent southern hemisphere was captured by NASA's Juno satellite as it made a close pass to the giant gas planet. Credit: NASA / JPL-Caltech / SwRI / MSSS / Kevin M. Gill

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, Massachusetts. "Having a database of close 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 more than 3,000 kilometers 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

"With this new understanding of magnetic fields, in future scientific passages, we will begin to create a horizontal map of Jupiter's secular variation. It could also have applications for scientists studying the Earth's magnetic field, which still contains many mysteries to solve. "

The Daily Galaxy via JPL