Southwest Research Institute (SwRI) researchers now think they have found the answer to a puzzle that has lingered for nearly four decades involving Uranus and its unusual radiation environment.

When Voyager 2 completed its first and only visit to the planet in 1986, the spacecraft detected an unexpectedly intense electron radiation belt, far stronger than scientists had predicted. Comparisons with other worlds suggested that Uranus should not have produced such extreme values. The discovery left scientists questioning how a planet so different from the rest of the solar system could maintain such a powerful band of trapped electrons.

New investigations are offering a potential explanation. SwRI scientists propose that the conditions recorded by Voyager 2 may resemble events seen near Earth during major solar wind disturbances. Researchers now suspect that a solar wind feature known as a co-rotating interaction region was moving through the Uranian system at the time of the flyby. If so, this passing structure could account for the unusually high energy levels Voyager 2 measured.