  The icy moon Europa is a primary target for the study of ocean worlds. Its
subsurface ocean is expected to be subject to asymmetries on global scales
(tidal deformation) and local scales (chaos regions, fractures). Here, we
investigate the possibility to magnetic sound local asymmetries by calculating
the induced magnetic fields generated by a radially symmetric ocean and a
small, spherical water reservoir between the ocean and Europa's surface. The
consideration of two conductive bodies introduces non-linear magnetic field
coupling between them. We construct an analytical model to describe the
coupling between two conductive bodies and calculate the induced fields within
the parameter space of possible conductivity values and icy crust thicknesses.
Given the plasma magnetic field perturbations, we find that a reservoir cannot
be detected during a flyby at 25 km altitude using electromagnetic induction.
Potential detection of liquid water reservoirs can be achieved by deploying
magnetometers on Europa's surface, where one magnetometer is placed directly on
the target region of interest and a second one in the nearby vicinity as
reference to distinguish from global asymmetries. With this method, the
smallest reservoir that can be detected has a radius of 8 km and a conductivity
of 30 S/m. Larger reservoirs are resolvable at lower conductivities, with a 20
km reservoir requiring a conductivity of approximately 5 S/m.
