Earth–ionosphere waveguide Earth–ionosphere waveguide The Earth–ionosphere waveguide refers to the phenomenon in which certain radio waves can propagate in the space between the ground and the boundary of the ionosphere. Because the ionosphere contains charged particles, it can behave as a conductor. The earth operates as a ground plane, and the resulting cavity behaves as a large waveguide. Extremely low frequency (ELF) (< 3 kHz) and very low frequency (VLF) (3–30 kHz) signals can propagate efficiently in this waveguide. For instance, lightning strikes launch a signal called radio atmospherics, which can travel many thousands of miles, because they are confined between the
Atmospheric duct of astronomical objects and the Novaya Zemlya effect. Atmospheric duct In telecommunications, an atmospheric duct is a horizontal layer in the lower atmosphere in which the vertical refractive index gradients are such that radio signals (and light rays) are guided or ducted, tend to follow the curvature of the Earth, and experience less attenuation in the ducts than they would if the ducts were not present. The duct acts as an atmospheric dielectric waveguide and limits the spread of the wavefront to only the horizontal dimension. Atmospheric ducting is a mode of propagation of electromagnetic radiation, usually in the lower