Diurnal and Seasonal Variability of Uranus’ Magnetosphere from Global MHD Simulations

Uranus’ strongly non-axisymmetric internal magnetic field and extreme obliquity combine to produce a highly dynamic magnetosphere with pronounced diurnal and seasonal variability. The single flyby of Uranus’ magnetosphere by Voyager 2, together with limited remote sensing of the atmosphere and aurora, provides only partial constraints on how this system reconfigures as the planet rotates and evolves through seasonal phases. Here we use the BATSRUS magnetohydrodynamic (MHD) model to simulate Uranus’ magnetosphere and quantify changes in its large-scale structure over a rotation cycle and across seasonal phases. We present results for near-solstice and near-equinox conditions, enabling direct comparison of how the relative geometry of the planetary rotation axis, internal magnetic field, and solar wind alters magnetospheric topology, boundary locations, and current systems. Comparison with Voyager 2 observations shows that the model reproduces the observed large-scale configuration, including the temporal variability of the tail plasma sheet sampled during the flyby. We use the simulations to characterize how periodic rotation-driven reconfiguration differs between solstice and equinox. These results provide context for interpreting auroral observations from Voyager and HST, including how seasonal geometry may modulate auroral morphology and variability.