Investigation of sub-surface ocean induction on Jupiter's icy moon Europa

Abstract: Following previous studies, a theoretical model for the induced magnetic field by Europa, one of Jupiter's icy moons, is presented. The aim of the model is to find evidence for the existence of a sub-surface ocean on the moon. Moreover, the accuracy of the theoretical model is evaluated using data from the Galileo space probe and a discussion of improvements, with the upcoming mission JUICE in mind, is given. The magnetic field from Jupiter is modeled using a dipole field and the moon is assumed to have the properties of a perfect homogeneous conductive layer (i.e a superconductor with no resistance). Europa is assumed to possess an electrically conductive subsurface ocean with conductivity $\sigma$. As the moon orbits Jupiter, the moon will experience a time-varying magnetic field since the magnetic dipole axis is tilted with an angle with respect to the rotation axis of the planet. The fact that the moon experiences a time-varying magnetic field will cause an inductive response inside the moon if a conductive material is present.  However, since this set-up reflects the ideal case, a discussion of constraints and improvements is submitted as a compliment. This thesis shows that the ocean model for Europa is supported, but further evidence is needed to fully understand the structure of the moon. The model shows a clear induction in almost all Galileo-flybys investigated, especially flyby E4 and E14. Thereby, it can be argued that the model gives a representative picture of the true induced magnetic field, with room for improvement.  In conclusion, further data is needed to fully reveal the structure of the moon, a fact that lays the foundation for the coming JUICE mission. JUICE will study both the magnetic and the electric field of Jupiter, and analyze the inner structures of the Galilean moons with higher precision than ever