Large scale eruption events in the solar atmosphere can generate global waves, i.e. waves which propagate over distances comparable to the solar radius. In the low solar corona, global waves observed by SOHO/EIT, generated by coronal mass ejections or flares are usually referred to as EIT waves. Since EIT waves carry information about their environment, they can be used for diagnostics of, e.g. the local and global magnetic field. This contribution presents theoretical models for finding values of magnetic field in the quiet Sun and coronal loops, and explores the physical connection between local and global solar coronal events (e.g. flares and coronal loop oscillations).