Neptune’s magnetic field is amazingly wild and could help us to improve our ability to forecast space weather events such as solar storms, according to a combination of 26-year old Voyager 2 data and supercomputer simulations, which sees the ice giant’s magnetism modelled in detail for the very first time.
Neptune is a mysterious planet. Only being visited by one spacecraft, there’s still much that we don’t know about the eighth world from the Sun. While data from Voyager 2, currently making its way to interstellar space, provides clues about the planet, more questions have been raised than answered. In particular, the ice giant’s magnetic environment seems to be lopsided. “Imagine taking the Earth, tipping it over diagonally, and then moving its magnetic north pole to central Europe, and you start to get a sense of what Neptune is like,” says planetary scientist Adam Masters from Imperial College London. “The planet’s unique magnetic field is still very poorly understood, and our new modeling represents a big leap forward.”
Neptune challenges even our basic understanding of how magnetic fields of planets and the distant worlds, known as exoplanets, behave. That’s why we must understand it. And, with no missions heading to the planet for many decades, Masters and his team took to simulations designed to understand plasma experiments in laboratories on Earth and applied them to environments in space. Plasma, which is dubbed ‘the fourth state of matter’, consists of electrically charged particles. It’s common in space and makes the magnetic fields that encompass planets form structures known as magnetospheres.
“Magnetic fields are tricky to understand, even when they are in simple systems. But Neptune is particularly badly behaved. Its odd properties challenge our basic ideas on how magnetospheres work,” says Masters of the results, which show Neptune’s magnetic field to be constantly rotating and changing. “Modeling a whole planet is no easy task. But supercomputers now make it possible and the new simulations explain a lot of what Voyager saw all those years ago. We can now see how the solar wind (the stream of electrically charged particles from the Sun) enters and circulates around Neptune’s magnetic field. The combination of the dramatic planetary rotation and this circulation pattern is why Voyager 2 found a ‘lopsided’ magnetosphere.”
Getting to know Neptune will help astronomers understand the large number of worlds found outside of our Solar System that are the same size as the ice giant. Despite being one of the most exotic planets in our Solar System, it can also play a key role in controlling the space weather that bombards our planet regularly by improving our ability to forecast solar storms.