The region between 80 km to 400 km above the surface of the earth, called ionosphere, plays a very vital role in the propagation of electromagnetic waves. Ionosphere is mostly composed of free electrons and ions which are produced due to ionisation caused by ultraviolet radiations and X-rays coming from the sun. Electron density is found to vary very largely beyond 110 km and extend vertically beyond 110 km. This layer of electrons is called Kennelly heavy side layer. Beyond this, electron density decreases considerably upto a height of 250 km. A layer of electron is again there and is called Appleton layer.
Both these layers play significant role in the conduction of electromagnetic waves.
