Surface Electromagnetic Waves at Gradual Interfaces between Lossy Media

A low loss propagating electromagnetic wave is shown to exist at a gradual interface between two lossy conductive media. Such a surface wave may be guided by a seafloor-seawater interface, and it may be used in radio communication and imaging underwater. It should allow communication distances of the order of 500 m at 10 kHz along a sandy seabed. Similar surface waves may also be guided by various tissue boundaries inside a human body. For example, such surface wave solutions may exist at planar interfaces between skull bones and grey matter inside a human head at 6 GHz.