Poynting Fluxes, Field-Aligned Current Densities, and the Efficiency of the Io-Jupiter Electrodynamic Interaction

Abstract

Juno's highly inclined orbits provide opportunities to sample high-latitude magnetic field lines connected to the orbit of Io, among the other Galilean satellites. Its payload offers both remote-sensing and in-situ measurements of the Io-Jupiter interaction. These are at discrete points along Io's footprint tail and at least one event (12th perijove) was confirmed to be on a flux tube Alfvénically connected to Io, allowing for an investigation of how the interaction evolves down-tail. Here we present Alfvén Poynting fluxes and field-aligned current densities along field lines connected to Io and its orbit. We explore their dependence as a function of down-tail distance and show the expected decay as seen in UV brightness and electron energy fluxes. We show that the Alfvén Poynting and electron energy fluxes are highly correlated and related by an efficiency that is fully consistent with acceleration from Alfvén wave filamentation via a turbulent cascade process.