2. A region of the earth's atmosphere where ionization caused by incoming solar radiation affects the transmission of radio waves.
It extends from a height of 70 kilometers (43 miles) to 400 kilometers (250 miles) above the surface.
3. A section in the earth's atmosphere, beginning at an altitude of 70-80 kilometers and extending to an indefinite height, in which free electrons and ions produced by solar radiation are abundant and affect certain radio waves that propagate through this region.Ionosphere and Magnetosphere
The ionosphere and the magnetosphere consist of regions of the 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 (mainly from the sun) on neutral atoms and molecules of air.
The ionosphere begins at a height of about 50 kilometers (30 miles) above the surface, but it is most distinct and important above 80 kilometers (50 miles).
In the upper regions of the ionosphere, beginning several hundred kilometers above earth’s surface and extending tens of thousands of kilometers into space, is the magnetosphere, a region where the behavior of charged particles is strongly affected by the magnetic fields of the earth and the sun.
Much of the early research on the ionosphere was carried out by radio engineers and was stimulated by the need to define the factors influencing long-range radio communication.
It is in the magnetosphere 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.
The name ionosphere was introduced first in the 1920's and was formally defined in 1950 by a committee of the Institute of Radio Engineers as "the part of the earth's upper atmosphere where ions and electrons are present in quantities sufficient to affect the propagation of radio waves."
Subsequent research has focused on understanding the ionosphere as the environment for earth-orbiting satellites and, in the military arena, for ballistic missile flight.
Scientific knowledge of the ionosphere has grown tremendously, fueled by a steady stream of data from spacecraft-borne instruments and enhanced by measurements of relevant atomic and molecular processes in the laboratory.
The ionosphere is the part of the atmosphere in which the air is ionized by such factors as the sun's ultraviolet radiation.
Layers within the ionosphere are also responsible for reflecting radio waves and are important to long-distance communication.
2. A region above a planet where the breakup of atmospheric gases by sunlight leads to large concentrations of free electrons and ions.These are capable of seriously disrupting radio communications on earth.