Excitation of the earth-ionosphere waveguide by an ELF source in the ionosphere

It is shown that for polar regions, where the conductivity is predominantly reactive, the wave functions for the transverse electromagnetic mode of the earth-ionosphere waveguide are Hankel functions of the first kind with real argument; therefore they extend up to large heights over the polar ionosphere. A Green's function for the excitation of the waveguide by extended current or field sources in the ionosphere is obtained for an exponential ionosphere. The potential of ELF waveguide excitation by wireless antennas is discussed.