Uranus's Highly Nonaxisymmetric Magnetopause and Its Impact on Magnetic Reconnection

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Abstract
Mass and energy fluxes from the solar wind can access a planet's magnetosphere through dayside magnetic reconnection. The plasma and magnetic field conditions on either side of the magnetopause determine whether reconnection is suppressed. However, magnetosheath conditions are sensitive to the shape of the magnetopause, and deviations from axisymmetry manifest in the field and flow patterns. This effect is, therefore, not captured in analytical models that assume axisymmetric boundary shapes. Here we utilize the BATSRUS MHD model to study the extent to which nonaxisymmetry alters the conditions for reconnection at Uranus's dayside magnetopause and how this varies on diurnal and seasonal timescales. Specifically, in this work we study conditions based on plasma and magnetic field parameters near the magnetopause that are known to suppress reconnection, rather than modeling reconnection itself. The magnetopause boundary arises naturally in MHD simulations instead of being prescribed. We demonstrate quantitatively the deviation of Uranus's magnetopause shape from a paraboloid and capture the resulting modification in magnetosheath field and flow patterns. Further, we show that suppression of reconnection is highly diurnal, though reconnection is never suppressed on the entire dayside magnetopause. Finally, we outline the limitations of axisymmetric analytical models and present the various features not captured in those models.
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Funding Information
  • National Aeronautics and Space Administration (80NSSC24K1565)
  • National Aeronautics and Space Administration Postdoctoral Program

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