Magnetopause Reconnection Voltages During the Voyager 2 Flyby of Uranus

Uranus’ magnetosphere presents a unique system to examine global magnetic reconnection processes due to its location far from the Sun. We assess reconnection effectiveness during Voyager 2’s Uranus flyby, using a physics-based analytical model to calculate reconnection voltages applied to the magnetopause. For the first time, reconnection conditions are assessed at Uranus under real-time varying solar wind conditions (rather than steady conditions or a parameter study). Here we show that reconnection effectiveness varied considerably over the two weeks before Voyager 2 passed into the magnetosphere, with voltages fluctuating between ~0-76 kV; peaking and then sharply dropping off shortly before Voyager 2’s entry. Variability in the voltages was found to be strongly influenced by Uranus’ extreme magnetic obliquity driving diurnal modulation. Furthermore, changes in solar wind conditions, in particular density and interplanetary magnetic field strength were found to drive additional variations which disrupts the expected ~17-hour periodicity of the voltages.