Spatially Variable Electron Beams in Io's Northern Alfvén Wing and Downstream Region

We report on 0.032–32 keV electron observations during two Juno flybys of Io on 30 December 2023 and 3 February 2024. The first explored Io's northern Alfvén wing, the second covering its downstream region, south of the plasma wake. Both had closest approach altitudes of ∼1,500 km. Lower fluxes of >32 eV electrons in the Io torus transitioned to higher fluxes of energized, field-aligned electrons within these regions. The electron fluxes were spatially variable within the Alfvén wing, highest at the boundaries, the distributions evolving from bi-directional to mono-directional as Juno traversed this region. Electron fluxes in the downstream region were also field-aligned, energized, and comparable to those during the northern flyby, supporting the interpretation of a glancing encounter with the southern Alfvén wing. The electron energy flux in these regions ranged from 1–15 and 2–22 mW m⁻², respectively, which are enhanced compared to estimates from Galileo.