Models using Voyager 2 data from the 1980s show that separate layers in the mantles of the planets Uranus and Neptune could be creating disordered magnetic fields.

In 1986 and 1989, Voyager 2 made the final two stops on its grand tour of the outer solar system when it swept by Uranus and Neptune, respectively. Now, nearly 40 years later, the archive of data the craft collected is still returning unexpected results. In the paper ‘Phase separation of planetary ices explains nondipolar magnetic fields of Uranus and Neptune‘, astronomer Burkhard Militzer of the University of California, Berkeley wanted to explore why Voyager 2 data show something unexpected: The magnetic fields of both planets, which are not that far apart in mass, are not dipolar. Earth, Jupiter, and Saturn all have dipolar magnetic fields, meaning they have a north and south pole — the type of configuration we’re obviously used to. But Uranus and Neptune don’t. Instead, their magnetic fields are more of a jumbled maze than an ordered set of lines.

Links:
Uranus and Neptune have weird magnetic fields — this might be why

What lies beneath the bland surfaces of Uranus and Neptune?