A Seasonal Study of Uranus’ Magnetosphere

Abstract:

The magnetospheres of the ice giant planets Uranus and Neptune are distinct from those of other major planets, including Earth, Jupiter or Saturn, because of their unique magnetic geometry: large obliquity, off-centered dipole moment, highly tilted angel between rotational axis and magnetic axis, and rapid rotation. We investigate the locations and shapes of critical boundary layers within these magnetospheres, specifically the bow shock, magnetopause and magnetotail, in order to more fully understand the complex interaction of the solar wind with these planets. To perform this study, we implement a multifluid MHD simulation capable of modeling the interplanetary solar wind interaction with the intrinsic magnetic field of the ice giant planets. These simulations are useful in that they can track individual fluids for electrons and different ion species and sources, which is important for understanding the interaction at the ice giant planets where differentiating between natively sourced ionospheric ions and externally sourced solar wind ions may be necessary due to their inherently different temperatures and compositions. Our simulations demonstrate that Uranus has an asymmetric and dynamic magnetosphere during solstice conditions, and that the asymmetry of magnetosphere might be quasi-periodic with rotation. We also investigate the magnetic structure and current systems in the magnetotail region, which can be used to understanding the global transport of plasma within the magnetosphere and hence dynamic responses to solar wind forcing and substorms. We will also present new simulations of Uranus’ global magnetosphere for equinox conditions, and provide predictions for auroral locations which we will then place in the context of recent Hubble Space Telescope observations.