Jupiter’s low-altitude auroral zones: Fields, particles, plasma waves, and density depletions
Journal Article
Overview
abstract
The Juno spacecraft’s polar orbits have enabled direct sampling of; Jupiter’s low-altitude auroral field lines. While various datasets have; identified unique features over Jupiter’s main aurora, they are yet to; be analyzed altogether to determine how they can be reconciled and fit; into the bigger picture of Jupiter’s auroral generation mechanisms.; Jupiter’s main aurora has been classified into distinct “zones”, based; on repeatable signatures found in energetic electron and proton spectra.; We combine fields, particles, and plasma wave datasets to analyze Zone-I; and Zone-II, which are suggested to carry the upward and downward; field-aligned currents, respectively. We find Zone-I to have; well-defined boundaries across all datasets. H+ and/or H3+ cyclotron; waves are commonly observed in Zone-I in the presence of energetic; upward H+ beams and downward energetic electron beams. Zone-II, on the; other hand, does not have a clear poleward boundary with the polar cap,; and its signatures are more sporadic. Large-amplitude solitary waves,; which are reminiscent of those ubiquitous in Earth’s downward current; region, are a key feature of Zone-II. Alfvénic fluctuations are most; prominent in the diffuse aurora and are repeatedly found to diminish in; Zone-I and Zone-II, likely due to dissipation, at higher altitudes, to; energize auroral electrons. Finally, we identify sharp and well-defined; electron density depletions, by up to two orders of magnitude, in; Zone-I, and discuss their important implications for the development of; parallel potentials, Alfvénic dissipation, and radio wave generation.
