Echoes of Radio Waves

Following the magneto-ionic theory of Appleton-Hartree, an explanation for the existence of echoes of long delay has been formulated. Realizing that the ordinary and extraordinary rays have opposite senses of polarization, it may be seen that one of these rays will penetrate the E layer while the other may not. The wave which penetrates the E layer will be reflected back from the F layer to the E layer and being repeatedly reflected between the two layers will travel around the earth and finally back to the ground. This time delay will account for the existence of echoes of long delay.