The Ionosphere RNAV
The ionosphere consists of three layers: D, E and F. Of these, the D layer is responsible for attenuating waves and the E and F layers are responsible for refracting waves back. Because the sun goes down, at night, the D layer disappears and the E and F layers move up. This is the cause of night effect - where waves that would normally be attenuated are able to travel long distances and interfere with other signals. The refraction of the ionosphere is made use of for HFHF —1) Radio Waves: High Frequency2) Human Performance: Human Factors comms and HFHF —1) Radio Waves: High Frequency2) Human Performance: Human Factors Volmet. These are longe range systems.