Ion Cyclotron Waves Associated With Ionospheric Outflow at Jupiter

Abstract The mechanism driving ion outflow from Jupiter's auroras remains to be determined. outflow has been observed with highly field‐aligned pitch angles consistent with acceleration by high‐altitude electrostatic potential structures. However, the cold ionospheric ions require a pre‐acceleration mechanism to reach Jupiter's large escape speed and access the potential structures. Here we present case studies of outflow coincident with intense ion cyclotron waves (ICWs). We invoke resonant wave heating to suggest a causality between the two phenomena. We further investigate Landau resonance with auroral electron beams as a plausible source of free energy using cold plasma theory, finding that electron energies between 10 and 100 keV produce results consistent with ICW observations. and ICWs are likewise present, which we suggest indicates that Jovian ion outflow is a multi‐species process.