Energetic Neutral Atoms from Jupiter's Polar Regions

Energetic Neutral Atom (ENA) cameras on orbiting spacecraft at Earth and Saturn helped greatly to diagnose these complex magnetospheres. Within this decade, the European Space Agency’s Jupiter Icy Moons Explorer (JUICE) will make ENA imaging a major thrust in understanding Jupiter’s complex magnetosphere. The present polar-orbiting Juno mission at Jupiter carries no ENA camera.  But, the energetic particle JEDI instrument is sensitive to >50 keV ENA’s, provided there are no local charged particles to mask their presence.  Juno offers great service to interpreting past serendipitous and future dedicated ENA imaging with its orbit providing unique viewing perspectives. Here we report Juno observations of ENAs from Jupiter’s polar regions.  These ENAs likely arise from energetic ions that nearly precipitate in the main auroral regions and mirror magnetically within, and charge exchange with, Jupiter’s upper atmosphere. Jupiter proves itself different from Saturn, as ENAs generated from precipitating ions were not identified there.