Juno Observations of Io's Alfvén Wing From 23 Io Radii

On 13 June, day 165 of 2024, Juno passed through Io's main Alfvén wing at a distance of ∼23 Io radii south of the moon during perijove 62. Evidence for this passage was clearly seen in the Juno plasma wave, magnetometer, and plasma data. The plasma wave signature was an intensification of quasi-electrostatic waves below about 1 kHz with a weaker magnetic component, all lasting for about two minutes. A strong perturbation of the magnetic field consistent with strong field-aligned currents was observed at the edges of the Alfvén wing. Ions in the range below about 1 keV/q were slowed within the Alfvén wing. As with other measurements in Io's Alfvén wing, we observe evidence of filamentation. The power in the Alfvén wing based on the measured Poynting flux is estimated to be ∼500–1,500 × 10⁹ W.