Electron densities in Jupiter's polar regions from the identification of Ordinary-mode wave cutoffs

Abstract

The electron density is a critical parameter for understanding auroral processes; namely, electron acceleration via Alfvénic dissipation, electrostatic acceleration, as well as the generation and propagation of radio and plasma waves. Inferring electron densities using plasma wave spectra at the polar-most regions of Jupiter is complicated by very intense low-frequency plasma wave emissions obscuring the low-frequency cutoff, i.e., the electron plasma frequency, of the ordinary-mode waves that are routinely observed in the sub{auroral and main auroral latitudes. Furthermore, low signal-to-noise ratios and count rates hinder the derivation of electron densities from plasma moments poleward of the diffuse aurora. Here, we introduce a new technique, whereby the E/cB spectra can be utilized to reveal the Ordinary-mode wave's cutoff, enabling accurate constraints on the electron densities at latitudes poleward of the main emission.