Io's Effect on Energetic Charged Particles as Seen in Juno Data

On 12 February 2019, the Juno spacecraft crossed the particle drift shells (L shells) of the moon Io. The energetic particle detector, Jupiter Energetic Particle Detector Instrument (JEDI), found very low fluxes of energetic protons when the spacecraft was inward of about L~6.5. Recent modeling suggests wave‐particle interactions may explain why energetic proton fluxes measured at these radial distances are low. JEDI also measured both a wide and a narrow decrease in the energetic electron count rate in Io's wake. At the time of this decrease, the JEDI detectors were dominated by 0.42 to 10‐MeV electrons. The dimensions of the narrow count rate decrease are about three Io diameters and are unlikely to be caused by absorption by moon itself. Key Points Energetic proton fluxes are observed to fall off moving radially inward toward Io's orbit A radially narrow decrease in energetic electrons within a wider decrease is found along Io's orbit on the wake side of the moon The mechanism most consistent with the narrow decrease is wave‐particle interactions near Io