Studying the mystery of Uranus’s curiously weak radiation belts

When the Voyager 2 spacecraft visited Uranus virtually 50 years in the past, it discovered a magnetic mystery. In contrast to on most planets, the ice giant’s magnetic area is tilted roughly 60° away from its spin axis, creating an uneven magnetic area that varies in energy. Understanding the explanation behind this anomaly is a key objective of NASA’s proposed flagship mission to the ice giants.

The planet’s tilted magnetic field can also be possible behind one other curious discovering from the Voyager 2 mission, in response to new research from M. Acevski and colleagues printed in Geophysical Analysis Letters.

A planet with a powerful magnetic area can seize charged particles from space, which then drift across the planet in what’s referred to as a radiation belt. The spacecraft’s devices detected proton radiation belts round Uranus far weaker than predicted—about 100 occasions decrease than the anticipated higher restrict. The authors have used new modeling to analyze why.

Most planetary area constructions could be modeled with a dipole area, however the researchers added a extra advanced quadrupole area of their mannequin to imitate the planet’s magnetic axial asymmetry. They used the Boris algorithm (usually used to simulate the motions of particles in an electromagnetic field) to mannequin the paths of charged particles surrounding Uranus.

They discovered that particles change velocity at varied factors of their orbits as they transfer via stronger and weaker areas of the uneven magnetic area. Notably, this impact seems solely when the magnetic area is modeled with the extra quadrupole area.

The authors say areas of elevated velocity unfold out the particles, lowering their density by as much as 20% in some areas across the planet. Voyager 2 may have handed via such a low-density space, they counsel, which can clarify why the craft discovered fewer particles within the radiation belts than anticipated.

This does not absolutely account for the radiation belt weak spot noticed by Voyager 2. However the information may assist to elucidate the mechanism behind Voyager 2’s findings and supply new theoretical information on the results of the planet’s magnetic area.

The proposed flagship mission to Uranus may present extra information, doubtlessly serving to us perceive the mechanisms behind the planet’s uncommon magnetic area.

This story is republished courtesy of Eos, hosted by the American Geophysical Union. Learn the unique story here.