A Localized and Surprising Source of Energetic Ions in the Uranian Magnetosphere Between Miranda and Ariel. Issue 8 (16th April 2023)

• Record Type: Journal Article
• Authors: Cohen, Ian J.; Turner, Drew L.; Kollmann, Peter; Clark, George B.; Hill, Matthew E.; Regoli, Leonardo H.; Gershman, Daniel J.
• Is Part Of: Geophysical research letters. Volume 50:Issue 8(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2023-04-16
• Subjects: Uranus -- planetary magnetospheres -- Voyager 2 -- energetic particles -- ocean worlds; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2022GL101998
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: In situ exploration of Uranus has been limited to a single flyby encounter by the Voyager 2 spacecraft in January 1986. Nonetheless, new investigation has led to significant questions about the origin of energetic ions observed in the region between its moons Miranda and Ariel. Radial and pitch angle diffusion modeling suggests that typical magnetospheric sources cannot explain the observed characteristics of these energetic ions. We suggest that these are likely being introduced by a source from one of these moons and give rise to waves that could result in the observed particle distribution characteristics. This may reveal that internal plasma sources in the system may be important for Uranus' magnetospheric dynamics and may contribute to its unexpectedly strong radiation belts. Plain Language Summary: Uranus is an oddity in the solar system for a variety of reasons, but mostly as a result of its perpendicular rotation relative to the rest of the planets in the solar system. During its approximately 3‐day flyby of Uranus in 1986, Voyager 2 captured the only in situ observations of the planet and its system. New analysis of these three‐decade‐old observations have revealed a mysterious source of energetic ions in the planet's magnetosphere. These ions were originally explained by dynamics of the system, but new understanding suggests that this is probably unlikely. New simple modeling of the expected behavior of such energetic particles show that sustaining such a population requires a very strong source and specific energization mechanism. Both would potentially be consistent with the ions originating from either Miranda or Ariel. This potentially hints that the Uranian magnetosphere may harbor an ocean world like those known or believed to exist at the other Giant Planets. Key Points: Analysis of Voyager 2 observations revealed a localized source of energetic ions in the region between the moons Miranda and Ariel Diffusive transport modeling suggests that typical magnetospheric sources cannot explain the observed characteristics of the energetic ions Additional in situ ion composition and plasma wave observations are necessary to confirm whether these ions are coming from an active moon