0-9 | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z
In the ionosphere, a layer that has a free-electron density sufficient to reflect radio waves. Note: The principal reflecting layers are the E, F1, and F2 layers in the daylight hemisphere. Note 2: A critical frequency is associated with the reflection by each layer.