The thermosphere is the part of atmosphere that lies beyond
mesosphere. It can be divided into two layers i.e. the ionosphere and the
exosphere.
The ionosphere is the lower part of the thermosphere. It
lies beyond the mesopause. It extends from 80 to 640 km. Temperature rises
sharply here. The ultraviolet radiation {UV rays} break the gas molecules here
into electrically charged ions. Therefore the ionosphere is full of
electrically charged ions which enable wireless transmissions. The upper limit of
the ionosphere is ionopause.
The exosphere lies beyond the ionopause and is the uppermost
layer of the thermosphere. The upper limit of the exosphere is difficult to
determine as it merges with the inter- planetary space.
The temperature here
is estimated as to be beyond 5500OC. The air is very thin and its
density is very low. Only the lighter gases like helium and hydrogen are found
here.
Nice explanation and good and clear image for easy understanding. Thanks...
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