Earth's Atmosphere.

The Ionosphere lies within the 
Thermosfeer as shown.

The ozone layer lies within the upper  
Stratosphere.

Between the Troposphere and the 
Stratosphere lies the Tropopause, 
between the Stratosphere and the 
Mesosphere lies the Stratopause and
between the Mesosphere and the 
Thermosphere lies the Mesopause.
(all thin layers)

Radio transmission waves are 
reflected on the Ionosphere so they 
can travel around the world.