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New insight and hypotheses on Uranus’ magnetosphere and its interactions with its moons, ionosphere, and atmosphere

Presentation #309.09 in the session Giant Planet Magnetospheres, Ionospheres and Aurorae (Oral Presentation)

Published onOct 23, 2023
New insight and hypotheses on Uranus’ magnetosphere and its interactions with its moons, ionosphere, and atmosphere

We present new results from an investigation of the unique magnetosphere of Uranus and its interaction with the solar wind. Following previous seminal work, we developed and validated a simple yet insightful model of Uranus’ offset, tilted, and rapidly-spinning magnetic field and magnetopause (a simplified, static fit to the Voyager-2 inbound crossing point) in three-dimensional space. With this model, we investigated details of the seasonal and interplanetary magnetic field (IMF) orientation dependencies of dayside and flank reconnection along the Uranian magnetopause. We found that anti-parallel (magnetic field shear angle greater than 170-degrees [i.e., Masters, 2014]) reconnection occurs nearly continuously along the Uranian dayside and/or flank magnetopause under all seasons of the 84 (Earth) year Uranian orbit and all of the most likely IMF orientations. We present hypotheses that such active and continuous driving of the Uranian magnetosphere should result in constant loading and unloading of the Uranian magnetotail, which may be further complicated and destabilized by sudden changes in the IMF orientation and solar wind conditions plus the reconfigurations from the rotation of Uranus itself. Our simple model is also used to map signatures of dayside and flank reconnection down to the Uranian ionosphere, as a function of planetary latitude and longitude. Such mapping demonstrates that “spot”-like auroral features should be very common on the Uranian dayside, consistent with observations from Hubble Space Telescope. With analogies to the latest in research from Earth’s magnetosphere, we further detail how the combination of Uranus’ rapid rotation and unique and very active magnetotail and global magnetospheric convection may be a non-negligible energy input into the Uranian ionosphere and also should be consistent with fueling of the surprisingly intense trapped electron radiation environment, which was observed by Voyager-2 during its single flyby and likely serves as a distinct weathering mechanism of the Uranian moons and also a significant energy input into the Uranian ionosphere-atmosphere system. Summarizing, Uranus is a very special magnetosphere that offers new insights on the nature, complexity, and diversity of planetary magnetospheric systems and the acceleration of particles in space plasmas. Our results highlight why any future mission to orbit Uranus should include a complement of magnetospheric instruments in the payload.

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