The High-Latitude Extension of Jupiter's Io Torus: Electron Densities Measured by Juno Waves

We present Jovian electron densities measured by the Juno Waves instrument at high-latitudes (with magnetic latitudes of (Formula presented.) on magnetic field lines threading the Io torus and plasma sheet (with M-shells of (Formula presented.)) using the first 29 orbits of the Juno mission. We infer electron densities from characteristic frequency cutoffs and resonances in plasma wave spectra. Often more than one of the characteristic frequencies of the plasma can be identified, whose consistency provides credibility to the plasma density estimates. The majority of density measurements are on magnetic field lines threading the Io torus and intersecting Jupiter's ionosphere between Io's M-shell and the auroral main oval, but there is evidence of density dropouts near and poleward of the auroral oval, which may be important in auroral particle acceleration. Sharp density gradients are found near field lines mapping to the inner edge of the Io torus M-shells. These observations demonstrate the extension of elevated Io torus densities along field lines to higher latitudes.