Magnetosheath jets are fast plasma streams that form in the region between a planet’s magnetic field and the solar wind, the stream of charged particles that come from the Sun. It’s an area of peculiar magnetism where the field lines are weak and irregular, and the jets play an important role. These temporary events have been found around Earth and Mars, and now researchers report that even Jupiter has them.
The biggest planet in the Solar System has a magnetic field that is 20,000 times stronger than Earth’s own. If we could see the radiation it creates with the naked eye, it would appear three times larger than the Sun or the Moon in the sky: A magnetosphere so large that it begins to push against the solar wind 3 million kilometers (1.86 million miles) from the planet. In that incredible environment, researchers found evidence of three magnetosheath jets.
Data from Voyager 2, which visited Jupiter in 1979, have been reanalyzed by astronomers from the Harbin Institute of Technology in Shenzhen. They report evidence for the presence of three of these jets, one moving towards the Sun and two moving away from the Sun. These jets extend from the bow shock, the region where the solar wind slams into the magnetic field. The solar particles are heated and slowed down by the magnetic field, in this case, that of the planet Jupiter.
The team compared the size of these jets with the size of the bow shock around Jupiter, Mars, and Earth. It seems that these plasma jets' sizes scale with the size of the bow shock. So Jupiter and its massive magnetosphere have massive jets, while Mars's modest interaction with the solar wind – lacking a planet-wide magnetic field – has much smaller jets.
Finding jets around a magnetic powerhouse like Jupiter is not groundbreaking, but tentative observations of jets were also seen around Mercury. The smallest planet in the solar system has a very weak magnetic field, about 1.1 percent of Earth’s own. The team looked at data from Cassini, an international mission to Saturn, and analysis suggests that similar structures could also exist around Saturn.
While the data from Mercury and Saturn is not as strong as the rest, the team believes that this plasma behavior is very common among planets and that jets might even be interacting with the moons of the gas giant. Titan, for example, would travel in that region of Saturn’s magnetosphere when on the dayside of the planet. However, the details of these behaviors will require a lot more studies.
A paper describing this research is published in the journal Nature Communications.