The Appleton layer (after the British physicist Edward Victor Appleton ), also known as the F layer , is the highest ionospheric layer on earth. Short-wave radio signals are reflected in the ionosphere , so it is most important for the propagation of the sky wave of radio signals.
The F-layer is divided into two sub-layers:
- The lower F1 layer ranges from 150 to 220 km and is only available during the day. It consists of a mixture of positively charged O + -, O 2 + - and NO + - ions .
- The F2 layer, which primarily consists of positively charged, atomic oxygen O + , spreads over the F1 layer between 220 and 800 km in altitude .
At noon, the F1 layer has approx. 5 × 10 5 free electrons per cm 3 with minimal solar activity ; With increased solar activity, the charge carrier density can reach up to 2 × 10 6 electrons per cm 3 . At night, the electron density of the F1 layer drops to below 10 4 electrons per cm 3 .
→ Main article: Ionosphere # F-layer