Polarization effects for subionospheric ELF/VLF signals penetrated into the seawater

Our study of electromagnetic wave penetration into the seawater was based on wide-band synchronous measurements of ELF/VLF atmospherics on the sea surface and underwater. Two crossed horizontal magnetic field components just above the sea surface and one horizontal electric component of underwater field have been examined to find the transfer function of a seawater layer of some 15 m in thickness. Using linearly-polarized antennae caused a number of polarization effects in the transfer function. The most prominent of the effects is that the water layer behaves as a spatial filter for modes in the Earth–ionosphere waveguide, making the transfer function irregular.