The ionosphere, the uppermost part of the atmosphere,
is the name given to the area of space approximately 70 km above the Earth's
surface. It is a plasma, consisting of free electrons and positive ions. It is above the
mesosphere (we live in the troposphere) and below the magnetosphere.
It is created and maintained by solar radiation. Particles in the solar wind ionize the
particles in the ionosphere. The level of ionization thus depends on solar activity (i.e.
it increases during solar storms).
Radio waves are electomagnetic waves that are affected by the ionosphere (in the same way
that our laser beam was affected by the water). They can be transmitted, reflected, refracted
and absorbed. The study of radio waves and the ionosphere is important because the ionosphere
affects radio signals, satellite communications and radar: all technologies used every day.