Spatial Distribution of Ion Cyclotron Waves at Io

Abstract Ion cyclotron waves at Io are important for understanding the complex interactions between Io and Jupiter's magnetosphere. In this study, we analyze the spatial distributions of ion cyclotron waves at Io using data from seven close flybys of Io—five by Galileo and two by Juno. We find that the amplitudes of ion cyclotron waves vary from several nT to ∼100 nT. The averaged wave amplitude reaches its peak at ∼2 R I downstream of Io and diminishes significantly with increasing distance from Io. While ion cyclotron waves are primarily observed downstream of Io, they also occur upstream but with much weaker amplitudes. Notably, these waves are absent within Io's Alfvén wings and plasma wake, likely due to the unique plasma environment in these regions. Our findings shed new light on the distribution properties of ion cyclotron waves at Io, which provide key inputs for exploring the interactions between Io and Jupiter.