Effects of a Nonlinear Treatment of Io's Interaction With the Jovian Magnetosphere

Io's interaction with the corotating plasma torus excites Alfvén waves which propagate through Jupiter's magnetosphere. They are partly reflected at density gradients and a complicated wave field develops downstream of Io. The Io-related auroral emission which serves as a screen for this wave field sometimes shows multiple footprints with variable distances as evidence of reflection processes. Therefore recent Hubble Space Telescope observations of the Io footprint morphology during the New Horizons flyby provide valuable constraints for the nature of the Io-Jupiter interrelation as well as for the reflection geometry. Here, we present nonlinear 3D-MHD simulations of this interaction with an improved magnetospheric model. We compare our findings to measured data and show the importance of including nonlinear effects especially for the description of MHD wave reflection. Moreover, we provide a possible explanation for the discrepancy between expected and measured inter-spot distances for different positions of Io in the plasma torus as well as the disappearance of multiple spots when Io is located in the torus center. Our results are also applicable to other moon- magnetosphere interactions, in particular to the Saturnian moon Enceladus.