Ale Moss, age 11, of St. Catharines.. Ontario, or his question:
Where is the ionosphere?
The ionosphere is part of the atmosphere, way above our heads. Though it is made of thin air, it acts like a solid sounding board. We can thank it for sending back the electromagnetic waver of T.V., radar, long and short wave radio. Actually, it is a layer of electrically charged gas particles. It begins above the stratosphere, about 50 miles up, and continues up to about 500 miles. Here it merges with the thin, thin exosphere, the outer limit of the atmosphere which perhaps reaches up a thousand miles.
Gases behave very differently from liquids or solids and the air, of course, is a mixture of gases. Gases spread out to fill all available space and the more space they have, the thinner they become. On the other hand, they can be squeezed, or compressed. The entire atmosphere is estimated to weigh about 5,500 million, million tons. This means that there is terrific weight pressing down upon the bottom layer. Half of the bases in the atmosphere are compressed into a lower layer three and a half miles deep.
Above this layer, the air gets thinner and thinner until it finally peters out maybe 1,000 miles above our heads. Certain levels in the deep blanket of air have different characteristics. The lowest layer is called the troposphere. It is the dense and turbulent region which produces our changing weather. The troposphere reaches about five miles above the poles and soma eleven miles above the equator.
Above the troposphere is the stratosphere, a region of calm weatherless air which reaches up to about 50 miles. Above the stratosphere is the ionosphere. Up here the gaseous particles are exposed to particles from outside the earth.
They are struck by cosmic rays, particles from outer apace traveling at devastating speeds. They are bombarded by ultra violet rays and other radiations from the sun.
Countless molecules and atoms of gas crash in collisions. Electrons are shorn off and other particles stripped away. This upsets the electrical balance of an atom. We call these unbalanced particles ions and the ionosphere contains a great many ions and ionized atoms. This state of affairs produces a blanket of electric potential.
Broadcasting stations and radar sending units pour out powerful electromagnetic waves in straight lines in all directions. They cannot be bent around the curve of the earthts surface. Some of them angle up to the ionosphere. There they are stopped and angled down again. They strike the earth some distance from the broadcasting station. There they may be picked up by a receiving set or relayed to another station,
There are different layers in the ionosphere, which is more than 400 miles deep. At the bottom is the E layer, which is weakest. It sends back long wave radio. The center is the F.l layer which sends back longer wave lengths. At the top is the F.2 layer which sends back short wave radio.