Upward, MeV-class electron beams over Jupiter's Main Aurora

Jupiter’s poleward (Zone II) main aurora exhibits bi-directional electron acceleration; upward acceleration dominates but downward acceleration generates strong aurora. During Juno’s first perijove (PJ1), the upward acceleration manifested as narrow electron angular beams (within ~5° of the magnetic field) over the 30-1200 keV energy range of Juno’s Jupiter Energetic Particle Detector Investigation (JEDI). These beams can be simply connected (non-uniquely) to >10 to perhaps 100’s of MeV electrons that penetrated the radiation shielding of the camera head of the Magnetometer Investigation’s Advanced Stellar Compass (ASC). The most intense of those multiple MeV populations are shown to have been highly directional and propagating upwards. How auroral processes generate such beams is unknown. With azimuthal symmetry assumed (not demonstrated here), these beams provided >1026 s-1 of >30 keV electrons to Jupiter’s vast magnetosphere, a possibly critical and dominating source of energetic electrons to that region and ultimately to Jupiter’s radiation belts.