An international team of scientists has discovered that Jupiter is encircled by a dark ribbon, a feature corresponding to the magnetic equator of the planet. This discovery plays an important part in building a complete picture of the gas giant's magnetic field, which is much more complex than what we see on Earth.
The team used 13,501 images of Jupiter taken between 1995 and 2000 that recorded the emission of trihydrogen cation (H3+), one of the most abundant ions in the universe. This molecular setup forms in the ionized region of the atmosphere, and since it is electrically charged, it is a good tracer for magnetic fields.
The dark ribbon, the team found, is an area lacking in H3+ ions. For this to occur, they proposed that the ions move to the more magnetically active higher latitudes, leaving a band across the planet. The data also showed that most of the Jovian ionosphere is relatively smooth and uninteresting. The research is reported in Nature Astronomy.
“The first time we saw the dark ribbon winding its way around Jupiter in our data, we felt sure we were seeing something special at Jupiter," lead author Dr Tom Stallard, from the University of Leicester, said in a statement. "The result was so startling and yet clear, it took us all by surprise, and we strongly suspected and speculated that the feature was caused by Jupiter's magnetic equator.
“It was a great relief to us that a few months before our paper was published the first magnetic model of Jupiter was released from the Juno spacecraft, providing an unprecedented view of Jupiter's equatorial magnetic field, and the measured magnetic equator lined up almost exactly with our dark ribbon of emission.”
The Juno mission has spent the last two years detailing several important properties of Jupiter like never before. It has studied the magnetic field of the planet, its gravity, and used its suite of instruments to peer beneath the clouds. The Juno team has put forward evidence that suggests complex magnetic distortions are happening at shallow depths.
“Our measurements also support that, because even though the equator is surprisingly simple, we see lots of complexity in the ionosphere between the equator and the pole,” Stallard added. “This suggests Jupiter's magnetic field in these regions is much more complex than that of Earth. It also suggests that as Juno takes higher resolution observations, it will continue to reveal even more fine-scale complexity.”
These observations are helping to unveil the sheer complexity of Jupiter’s interior and show how little we know about the planet. Just last year, the team revealed the presence of the Great Cold Spot, a cooling region that rivals in size the dramatic storm known as the Great Red Spot.