Heavy-ion effect on the e.l.f. propagation beneath a loss-less anisotropic ionosphere

The heavy-ion effect on the spectrum of the surface waves guided along a vacuum-plasma boundary is discussed. The e.l.f. terrestrial propagation is shown to take place via this surface-wave mode, which is only very slightly perturbed by the presence of the Earth. As a result of the inclusion of the heavy-ion motion, the guided e.l.f. waves are found to acquire a low-frequency cutoff.