Plasma waves in Jupiter’s high latitude regions: observations from the Juno spacecraft

The Juno Waves instrument detected new broadband plasma wave emissions on the first three successful passes over the low altitude polar regions of Jupiter on Days 240 and 346 of 2016 and Day 033 of 2017. This study investigated the characteristics of these emissions and found similarities to whistler-mode auroral hiss observed at Earth, including the funnel-shaped frequency-time features. The electron cyclotron frequency was much higher than both the emission frequencies for all three days and the local plasma frequency, which was assumed to be 20 – 40 kHz. The electric to magnetic field (E/cB) ratio was around three near the start of each event and then decreased to one for the remaining duration of each pass. Spin modulation phase shifts were found on two of the three days (Day 240 and Day 033), indicating wave propagation up to the assumed plasma frequency. A correlation of the electric field spectral densities with the flux of up-going 20 to 800 keV electron beams on all three days were found, with correlation coefficients of 0.59, 0.72, and 0.34 for Day 240, Day 346, and Day 033 respectively. We conclude that the emissions are propagating in the whistler-mode and are driven by energetic up-going electron beams along the polar cap magnetic field lines.