Observation and interpretation of energetic ion conics in Jupiter's polar magnetosphere

NASA's Juno spacecraft successfully completed its first science polar pass over Jupiter's northern and southern aurora, with all the instruments powered, on 27 August 2016. Observations of conical energetic proton distributions at low altitudes (<6 R_J) over the northern polar region are interpreted as resulting from transversely (to the local magnetic field lines) accelerated H⁺ at a position planetward of the point of observation. The proton conics were observed within a broad region of upward beaming electrons and were accompanied by broadband low-frequency wave emissions as well as low-altitude trapped magnetospheric protons and heavy ions. The characteristic energies associated with these accelerated ion conics are ~100 times more energetic than similar distributions observed in the Earth's auroral region and similar in energy to those found at Saturn. In addition, the ion conics also exhibited pitch angle dispersion with time that is interpreted as a consequence of the structure of the source location. Mapping these distributions along magnetic field lines connected from the spacecraft to the ionosphere suggests that the source region exists at altitudes between ~3 and 5 R_J. These new and exciting observations of accelerated ions over the polar region of Jupiter open up new areas for comparative planetary auroral physics.