Io's Near‐Field Alfvén Wings and Local Electron Beams Inferred From Juno/Waves

Juno conducted two close Io flybys on 30 December 2023 and 03 February 2024, both at a minimum altitude of 1,500 km. Filamentary structures in the electric and magnetic field spectra indicate Juno crossed the Alfvén wing, the magnetic structure connecting Io to Jupiter's polar ionosphere. We show that the first pass took Juno diametrically through the northern Alfvén wing, while the second pass had Juno graze the southern Alfvén wing boundary, enabling extended measurements of the transition region between Io's vicinity and the Jovian magnetosphere. Of note, evidence of local electron beams is inferred from whistler‐mode emissions. We demonstrate that their energies are sub‐keV, are sourced from Io's ionosphere or local torus, and are part of a distributed current system connecting Io to Jupiter. Finally, upper hybrid resonances indicate electron densities are significantly elevated in Io's polar region (∼28,000 cm−3) compared to the local Io torus (∼2,000 cm−3). Plain Language Summary Juno conducted two close Io flybys. Signatures in the electromagnetic field indicate that Juno sampled the region dominated by the electrodynamic interaction between Io and Jupiter. Powerful electric currents flow within this region that deliver energetic electrons into Jupiter's polar atmosphere, resulting in the Io auroral footprint. Juno also spent an extended period along the boundary of this region, providing an in situ view of the complexity of this region's structure. Local density measurements indicate significantly elevated densities in Io's poles. Key Points Juno plasma wave observations are consistent with Alfvén wing crossings during close Io flybys Whistler‐mode radiation indicate the presence of sub‐keV electron beams operating just outside the Alfvén wing Electron densities are significantly elevated in Io's polar region