Juno/Waves Observations of Intense Broadband Electromagnetic Emissions below the Ion Cyclotron Frequency

During each perijove pass, Juno's Waves instrument detects intense broadband emissions across all frequencies up to a cutoff at the H⁺ cyclotron frequency. The emissions are most pronounced for over 30 minutes around closest approach, thereby covering a large range of latitudes as afforded by the highly inclined orbits. Appreciable power is present in both the electric field and magnetic field sensors, thus confirming their electromagnetic nature. These emissions are detected for the first time in one of the giant planets. We understand that, rather than an underlying physical process taking place uniquely at Jupiter, the very high magnetic field of its environment permits their detection. The H⁺ cyclotron frequency is up to 15 kHz, well within the instrument's range. This is in contrast with Saturn, where the frequency measured was up to 0.25 kHz during Cassini's Grand Finale phase, thereby too low to be detected. Given this unique opportunity at Jupiter, we analyze these emissions by constraining their spatial distribution as seen by Juno, examine their generation mechanism, and discuss the possible role they play in magnetospheric, ionospheric, and/or auroral processes.