The anomalous state of Uranus' magnetosphere during the Voyager 2 flyby

Voyager 2 revealed that Uranus hosts an unusual magnetosphere with a highly oblique and off-centered magnetic field. The properties of this complex magnetosphere, however, cannot be understood without carefully considering the role of external forcing by the solar wind. Here we show that Voyager 2 observed Uranus’ magnetosphere in a highly atypical, compressed state that we predict to be present <5% of the time. However, the prevailing understanding of the Uranian magnetosphere is based on this single observation, leading to a description of the system as a canonical extreme case, with inexplicably intense electron radiation belts and a magnetosphere that is seemingly largely void of plasma. Contrastingly, we show that had Voyager 2 arrived at Uranus just a few days earlier, the upstream solar wind dynamic pressure would have been ~20 times lower, resulting in Voyager 2 observing a dramatically different magnetospheric configuration.