Couche supérieure de l'atmosphère.
The outer region of the Earth's atmosphere; contains a high concentration of free electrons.
Ionized layer of Earth's outer atmosphere (60–1,000 km/38–620 mi) that contains sufficient free electrons to modify the way in which radio waves are propagated, for instance by reflecting them back to Earth. The ionosphere is thought to be produced by absorption of the Sun's ultraviolet radiation.