Environmental Science 3(3+0)

(5) Exosphere

Thermosphere

• 80 km and up - The air is very thin. Thermosphere means "heat sphere". The temperature is very high in this layer because ultraviolet radiation is turned into heat. Temperatures often reach 2000 degrees Celsius or more. This layer contains:

Ionosphere

• This is the lower part of the thermosphere. It extends from about 80 to 550 km. Gas particles absorb ultraviolet and X-ray radiation from the sun. The particles of gas become electrically charged (ions). Radio waves are bounced off the ions and reflect waves back to earth. This generally helps radio communication. However, solar flares can increase the number of ions and can interfere with the transmission of some radio waves.


• The region of atmosphere above the thermosphere is called exosphere or outer space which lacks atoms except that of hydrogen and helium and extends up to 32,190 km from the planet. It has very high temperature due to solar radiations. Air is very thin here. This is the area where satellites orbit the earth.