Auroral ion precipitation at Jupiter: Predictions for Juno

Abstract

The spatially localized and highly variable polar cap emissions at Jupiter are part of a poorly understood current system linking the ionosphere and the magnetopause region. Strong X-ray emission has been observed from the polar caps and has been explained by the precipitation of oxygen and sulfur ions of several MeV energy. The present paper presents results of an extended model of the ion precipitation process at Jupiter. Specifically, we add to a previous model a more complete treatment of ionization of the atmosphere, generation of secondary electron fluxes and their escape from the atmosphere, and generation of downward field-aligned currents. Predictions relevant to observations by the upcoming NASA Juno mission are made, namely the existence of escaping electrons with energies from a few eV up to 10 keV, auroral H2 band emission rates of 80 kR, and downward field-aligned currents of at least 2 MA.