Ganymede's magnetosphere: Unraveling the Ganymede-Jupiter interaction through combining multi-fluid simulations and observations.

摘要

The Galilean moon Ganymede provides a unique case study in furthering our understanding of how space plasmas interact with planetary magnetospheres. Ganymede is the largest of Jupiter's moons and the only one to have its own magnetosphere, which is embedded within the large Jovian magnetosphere. In order to understand the complex interactions in this system, we have implemented a novel three-dimensional modeling technique that represents different ion sources as collisionless fluids that interact via electric and magnetic fields. The results from this multi-fluid treatment are well correlated with observations of aurora and magnetic fields, and demonstrate the important role heavy ions and their gyromotion play in governing the shape and dynamics of Ganymede's magnetosphere. Predictions for the morphology of Ganymede's tail-side aurora were made using these simulations, which were later validated by the Hubble Space Telescope.; The multi-fluid nature of the simulations also allows one to track the differential acceleration of heavy and light mass ions sourced from Ganymede's ionosphere and the Jovian magnetosphere. Thus, sampling the simulated ion energies, temperatures and densities for each ion species along Galileo's trajectory permits the representation of simulated data in a way directly comparable to ion energy spectrograms from Galileo. This enables new interpretations of the heavily debated ionospheric outflow observations using a method based purely on the physics governing the magneto-plasma interactions of Ganymede's near space environment.