Auroral Ionospheric Erosion at Jupiter

The generation of Jupiter's main auroral oval is dominated by broadband‐energy electron beams, in contrast with the dominance of peaked electron energy spectra at Earth. Wave‐particle interactions involving Alfvén waves have been theorized to be the main mechanism driving the broadband acceleration of electrons. Alfvénic interactions are favored in the presence of density depletions and steep density gradients across adjacent magnetic field lines. Here we present electron densities at low altitudes (0.3–2.8 ) above the diffuse and main auroras inferred from frequency cutoffs in plasma wave spectra measured by the Juno/Waves instrument during the first 62 perijoves. We find that the electron densities above the diffuse and main auroras consistently decrease toward poleward latitudes and can be depleted down to the order of . Moreover, we show that the spatial gradient of the density depletion varies with altitude, and the peak in the density gradient occurs above 1 , suggesting altitudes at which Alfvénic acceleration is most likely. Finally, we find that these auroral density gradients are much steeper than are found in the non‐auroral ionosphere, indicating an active cavitation process connected with the aurora likely driven by the action of Alfvén waves.