The electrodynamic coupling between Io and Jupiter gives rise to wave-particle interactions across multiple spatial scales. Here we report observations during Juno's 12th perijove (PJ) high-latitude northern crossing of the flux tube connected to Io's auroral footprint. We focus on plasma wave measurements, clearly differentiating between magnetohydrodynamic (MHD), ion, and electron scales. We find (i) evidence of Alfvén waves undergoing a turbulent cascade, suggesting Alfvénic acceleration processes together with observations of bi-directional, broadband electrons; (ii) intense ion cyclotron waves with an estimated heating rate that is consistent with the generation of ion conics reported by Clark et al. (2020,

At the end of the Juno primary mission, we report observations of whistler mode chorus and Z‐mode emission. The Juno orbits are evolving and much better coverage of the whistler mode chorus source region has resulted since the earlier surveys. Bursty chorus emission extending to ∼30° latitude and to frequencies less than the lower hybrid frequency near the source region imply high electron energies (>100 keV). Average chorus intensity levels peak at ∼10−3 nT2 near M‐shell of 8–9 and magnetic latitude of ∼5°. Z‐mode emission is identified at higher latitudes generally near and inward of the Io torus with intensity levels as much as two orders of magnitude higher than Z‐mode emissions observed at Saturn. Inferred source regions for the Z‐mode are consistent with the inner edge of the Io torus and with auroral field lines that may also support Jovian kilometric and decametric emission. Parametric fitting functions are evaluated for both whistler mode chorus and Z‐mode, describing wave intensity as a function of frequency, magnetic latitude, and M‐shell. Both whistler mode and Z‐mode waves may have significant impact on electron scattering and acceleration at Jupiter as recent models indicate.

The Juno spacecraft's polar orbits have enabled direct sampling of Jupiter's low‐altitude auroral field lines. While various data sets 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 data sets to analyze Zone‐I and Zone‐II, which are suggested to carry upward and downward field‐aligned currents, respectively. We find Zone‐I to have well‐defined boundaries across all data sets. 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 significant electron density depletions, by up to 2 orders of magnitude, in Zone‐I, and discuss their important implications for the development of parallel potentials, Alfvénic dissipation, and radio wave generation.

Large amplitude electromagnetic plasma waves are observed simultaneously with intense fluxes of electrons precipitating on auroral field lines at Jupiter. Here we present plasma wave observations from the Juno Waves instrument obtained during an instance of very intense broadband electron precipitation observed by the Jupiter Energetic Particle Detector Instrument connecting to Jupiter's main auroral oval. The wave spectrum extends from 50 Hz to~10 kHz with peak-to-peak amplitudes of 10 nT in the magnetic channel and of~1 V/m in the electric channel, representing some of the most intense plasma waves observed by Juno. The E and B fields of these electromagnetic waves are correlated and have apparent polarization perpendicular to Jupiter's magnetic field with a downward Poynting flux. We conclude the plasma waves are whistler mode emissions with a possible admixture of ion-cyclotron or Alfvén waves and may be important in the broadband electron acceleration.Plain Language Summary Large amplitude whistler mode waves are found coincidently with intense fluxes of precipitating electrons across a broad energy range connecting to Jupiter's main auroral oval. The whistler mode waves are propagating downward, in the same direction as the precipitating electrons. The tight correspondence in time between the waves and the electrons strongly suggests an important interaction between the waves and electrons.