Night-time High Multiple Reflections from the F-Layer & Ionospheric Absorption

Abstract

High-multiple reflections are believed to be caused by focusing effects through wavelike disturbances in the reflecting layer. The frequency of occurrence of these echoes, however, shows seasonal and solar cycle variations. It is suggested that such variations are due to changes in the shape of the F-layer and consequent changes in deviative absorption in the rays reflected from the varying gradients of electron density.