Ionosphere

Ionosphere and magnetosphere, regions of Earth’s atmosphere in which the number of electrically charged particles-ions and electrons-are large enough to affect the propagation of radio waves. The charged particles are created by the action of extraterrestrial radiation on neutral atoms and molecules of air. The ionosphere begins at a height of about 50 km above the surface, but it is most distinct and important above 80 km. In the upper regions of the ionosphere, beginning several hundred kilometres above Earth’s surface and extending tens of thousands of kilometres into space is the magnetosphere, a region where the behaviour of charged particles is strongly affected by the magnetic fields of Earth and the Sun. It is in the lower part of the magnetosphere that overlaps with the ionosphere that the spectacular displays of the aurora borealis and aurora australis take place. The magnetosphere also contains the Van Allen radiation belts, where highly energized protons and electrons travel back and forth between the poles of Earth’s magnetic field.