ON VLF RADIO-WAVE REFLECTION FROM DISTANT MOUNTAIN-RANGES THEORY

We present an analysis for the reflection or scattering of VLF radio waves by gently sloping parallel ridges that may be well displaced from the great circle path between the transmitter and receiver antennae. It is shown that, under certain conditions, a spatial harmonic of the transverse profile of the terrain will produce a secondary signal that could be not far below the direct or primary signal. Such a resonant scattering mechanism may explain some of THOMSON's [(1989), J. atmos. terr. Phys. 51, 339] observations in Dunedin, New Zealand.