Auroral acceleration at Jupiter and its possible role in creating Jupiter’s uniquely energetic radiation belts

The electron acceleration processes that generate Jupiter’s uniquely powerful aurora are unexpectedly diverse. Broadband acceleration, likely stochastic, provides the greatest downward electron energy fluxes over Jupiter’s main auroral regions. But electric potentials along the main auroral field lines are sometimes present, at times exceeding 400 kV in either the upward or downward directions. Huge downward electron energy fluxes are unexpectedly observed on the very same field lines where huge electric potentials are also accelerating downward energy beams of protons. Using the magnetic field-aligned potential directionality as a proxy for the directionality of magnetic field-aligned electric currents, the magnitude of the downward electron energy fluxes surprisingly does not seem to care about the directionality of the electric currents. But the directionality of the electric potentials does seem to play a role in determining the character of the broadband acceleration processes and particularly in the up-down asymmetries in the acceleration processes. Surprisingly, even over very intense UV aurora, the upward acceleration of electrons can be comparable and even greater than the downward acceleration. And more surprising still, the intensity of the upwardly accelerated electrons at MeV energies can be as much as 2 orders of magnitude greater than the intensity of Jupiter’s radiation belts. Based on that finding, we explore here the possibility that, at Jupiter, auroral acceleration represents the first acceleration step in the generation of Jupiter’s uniquely energetic radiation belts.