Abstract
Observations of energetic charged particles associated with Io’s
footprint (IFP) tail, and likely within or very near the Main Alfvén
Wing, during Juno’s 12th perijove (PJ) crossing show evidence of intense
proton acceleration by wave-particle heating. Measurements made by
Juno/JEDI reveal proton characteristics that include pitch angle
distributions concentrated along the upward loss cone, broad energy
distributions that span ~50 keV to 1 MeV, highly
structured temporal/spatial variations in the particle intensities, and
energy fluxes as high as ~100 mW/m2. Simultaneous
measurements of the plasma waves and magnetic field suggest the presence
of ion cyclotron waves and transverse Alfvénic fluctuations. We
interpret the proton observations as upgoing conics likely accelerated
via resonant interactions with ion cyclotron waves. These observations
represent the first measurements of ion conics associated with
moon-magnetosphere interactions, suggesting energetic ion acceleration
plays a more important role in the IFP tail region than previously
considered.