The ionosphere is in the outer most part of our atmosphere or sky. If we can fly up in the air … right up past where any plane can fly … way past where the clouds are. You have to travel at least 60km straight upwards to get to the ionosphere! It is called the ionosphere because the air is very thin and the particles of air have the full force of the Sun on them. What happens is that the Sun "boils" these air particles and they become charged (like static electricity!). This is called photoionization. Very extreme ultraviolet light, x-rays and cosmic rays cause it. These forms of light are very dangerous!! Our ozone layer below this protects us from serious sunburn… the ionosphere is way above the ozone layer.

The ionosphere allows radio signals to travel by bouncing between the surface of the earth and the ionosphere. Therefore, a radio signal can travel to the other side of the earth by firstly being "fired" at the ionosphere and then it bounces back down to earth. At night the ionosphere gets bigger so therefore the radio signals can travel further at night than during the day. During the daytime across the north and south pole, photoionization is the main thing that makes the type of atmosphere … the ionospheric plasma.

The lower ionosphere is between 60 and 800 km away from the Earth. The main gases in the lower ionosphere are (nitrogen oxide) NO+ and (oxygen) O2+; and in the upper ionosphere, where most of the ionospheric plasma is, O+ is there. Even higher is a region called the plasmasphere. It is very cold and dense and it affects the electric field of the Earth.

You might want to look up about the Magnetosphere as well.