Structure of Earth's atmosphere

Earth atmosphere is not uniformly continuous but is divided in different layers because of their properties.

  • troposphere
  • stratosphere
  • mesosphere
  • thermo- or ionosphere
  • exosphere
Atmosphere of earth seen from space (Source: NASA)


p(z) = p(0) *e -z/H     p(z) ... Pressure at height z      p(0) ... Pressure on ground level      H ... scale height (5500 m)

Pressure and density shows an exponential progression. On the surface of earth we have a air pressure of about 1013 hPa, in about 5.5 km the pressure has decreased to about half. Every 5.5 km more the pressure decreases again about a factor of 2. This law is named barometric height formula.

Exosphere

The exosphere is the outermost component of earth atmosphere. In this region the gravitational forces on air particles are very weak. So some particles can already escape into space.

Thermo- or Ionosphere

This layer reaches a height of about 200km. The layer is named ionosphere because of the ions. In this layer a high concentration of ions can be found. A ion is a atom with more or less electrons than protons. The layer reflects radio waves coming from earth. This feature allows long range radio communication on earth.

Mesosphere

The mesosphere reaches heights of about 80 km. In the mesosphere temperature dropes to about -80°C. In the above thermosphere the temperature increases again and reaches finally temperatures of about 2000°C.

Stratosphere

The stratosphere reaches heights of about 48km. An interesting fact is the ozon layer in about 25 km height. By this layer the earth surface is shielded against high energetic ultra violet radiation.

Troposphere

The lowest layer is finally the troposphere. This layer reaches heights of about 15 km. In this region more then 90% of the mass of atmosphere is concentrated. Temperature decreases of about 6.5°C per kilometer. Also the troposphere is very important for mankind because the whole weather phenomena are produced their.

 
layering of earth atmosphere
out of "Die Eroberung des Sonnensystems, publisher:Kaiser"
 
 
 
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