Energetic Ion Losses Observed During Juno's Close Encounter With Europa

We present energetic ion observations made by Juno during its close Europa flyby on 29 September 2022. These data show significant reductions in the ion intensities occurring in the moon's geometric wake region. The most significant losses occur for locally mirroring ions with gyrophases on the anti-Jovian facing side of the wake. Ions with pitch angles >30° from the local perpendicular direction have guiding center trajectories that allow them to skip over the moon as they azimuthally drift with velocities ∼100 km s⁻¹. In general, short bounce times and large gyroradii can act as good indicators when to expect significant losses; however, we show asymmetries in energy, pitch angle, and gyrophase that we cannot fully explain and require detailed particle tracing with realistic electromagnetic fields. Finally, we compute ion integral fluxes along Juno's trajectory and show ∼85% of the near equatorially mirroring, >50 keV, ions are absorbed by Europa.