Juno Observations of Plasma Waves Associated with the Io Footprint Tail

The Juno spacecraft has crossed magnetic flux tubes associated with the Io auroral footprint tail at a variety of downtail distances from the Io footprint spot. The Juno radio and plasma wave instrument (Waves) detects large amplitude electromagnetic waves during many of these crossings. These emissions are usually detected for just a few seconds to tens of seconds and high resolution Wave burst data show that peak amplitudes of these waves can reach about 1 V/m for the electric field and a few nT for the magnetic field. However, on the recent perijove 12 northern crossing, the Waves instrument detected an intense funnel shaped emission lasting for many minutes with intense lower frequency emission at the funnel apex. Initial analysis of these emissions suggest that these waves are propagating upward from Jupiter. The emission frequencies are well below the electron cyclotron frequency and the upper frequency appears to be cutoff at the electron plasma frequency, with an additional change in intensity also observed at the proton cyclotron frequency. We will discuss the details of these waves and examine possible wave modes.