Thanks to NASA’s Juno mission, researchers have finally obtained a map of Jupiter’s magnetic field and it is quite something. The magnetosphere of Jupiter is not just very different from Earth’s, it is also unlike any other planet in the Solar System.
Scientists had evidence suggesting that the Jovian magnetic field was peculiar but the new analysis, published in Nature, shows just how complex the field really is. The planet has the standard dipole you might have seen in a diagram, the lines connecting the North and South Pole. But it's also much weirder. There is a long magnetic band in the northern hemisphere and also a large circular region in the south that the team has nicknamed the "Great Blue Spot". The spot is not actually blue, unlike Jupiter's giant red storm, the name comes from the color coding of magnetic fields, red for north, blue for south (just like in toy magnets).
These non-dipolar structures are very different from Earth’s. On our planet, the non-dipole regions are evenly distributed but on Jupiter, they are mostly found in the northern hemisphere. Although it cannot probe the core of the planet, Juno was able to measure that the northern hemisphere band becomes narrower with depth, suggesting that the region from which it originates is localized.
“The main surprise was that Jupiter’s field is so simple in one hemisphere and so complicated in the other," lead author Kimberly Moore told Newsweek. "None of the existing models predicted a field like that."
"We were also surprised to learn the Great Blue Spot is a singular feature in the field. When we first observed it on Juno’s first orbit, we thought there would be others like it, but that’s not the case,” she added.
The cause of the peculiar magnetic field is not exactly clear. The core of Jupiter is believed to be made of metallic hydrogen, a peculiar state where the common gas behaves like an electrical conductor. The team suggests that the core might be layered, with a top layer made of pure metallic hydrogen and a core layer where rocks and ice are dissolved in the hydrogen, just like salt is dissolved in seawater. There are also movements within the interior of the planet to take into account.
The team believes that there are ways to understand what actually goes on inside Jupiter. This map was obtained using eight flybys of the planet by Juno. By the time the mission ends in July 2021, the spacecraft will have complete 34 science flybys. And it will probably give us enough data to work out just what powers the strange magnetic field of the gas giant.