Structure of atmosphere

The Troposphere, the region of weather, extends from the ground to height of 10-12 km. in our lattitudes and to about 18 km. at the equator.In this region the temperature falls by about 6 C per km.At the upper boundary (the tropopause) the temperature is closely 219 absolute.The stratosphere lies above the troposphere and is characterized by the uniformity of the temperature which remains constant at 219 absolute in our lattitudes up to a height of about 30 km.Thereafter the temperature rises, attaining a value of about 370 absolute at 60 km.Above this height the temperature falls, reaching 184 absolute at 80 km while for greater altitudes the available evidence shows a continuing increase in temperature.The temperature at 110 km is about 347 absolute.The region between 30km and 80 km is called the mesosphere, that above 80 km, the thermosphere. Ozone occurs predominantly between 30 and 60 km.

The  Ionosphere consists during the day of three main ionized layers E,F1,and F2 which occur at heights of about 100, 200 and 300-400 km respectively.During night the F2 layer descends into approximate coincidence with the F1 layer .The ionosphere reflects radio waves back to the earth provided their frequencies are less than certain critical values.Critical frequencies vary with time of day and the sun spot cycle.If the frequency is greater than this value,the wave penetrates the ionosphere and escapes.

Auroral displays occur most frequently at about 100km in northern and southern latitudes.