Particle energization and structuring of Jupiter’s main auroral oval as diagnosed with Juno measurements of (>30 keV) energetic particles

Juno polar low-altitude energetic particle observations indicate that the most intense emissions from Jupiter’s main auroral oval are caused by the impingement onto the atmosphere of relatively flat, energy-monotonic electron distributions, often extending to energies >1 MeV. They can be associated with bi-directional angular beaming with upward fluxes greater than the downward fluxes. Downward fluxes of >800 mW/m^2 have been observed. However, when viewed in high time resolution ( 1.0s) these distributions are sometimes (3 of 8)) intermixed with >50keV downward accelerated electron distributions with the classic inverted-V configuration, indicative of steady magnetic field-aligned electric fields. The highest downward energy peak observed so far is 400 keV. The inverted-V energy distributions lack the high energy tails observed in adjacent regions, and thus, contrary to what is observed at Earth, the associated downward energy fluxes are generally lower than the downward energy fluxes associated with the more intense energy-monotonic distributions. The relationship between these two modes of auroral particle energization is unclear. Do the classic auroral processes that create inverted-V distributions become so powerful that instabilities are stimulated that cause stochastic energization to turn on and dominate, or do these two different forms of auroral acceleration represent distinctly different processes? These and other questions are explored.