Page 39 - Beginner's Guide to Aviation

1. Exosphere
Upper boundary: 10,000 km
Lower boundary: 500 - 1000 km
The uppermost and last atmosheric layer right before space. It contains some of the lightest gases such as hydrogen, helium, carbon dioxide and atomic oxygen.
2. Thermosphere
Upper boundary: 640 km
Lower boundary: 80 – 85 km
This layer is where the International Space Station (ISS) orbits. It is also where beautiful auroras occur. However, within this layer ultraviolet radiation causes ionisation which is harmful to us.
These two layers make up the Ionosphere because they are ionised by solar radiation. This solar radiation generates different layers of ionisation and influences radio propagation.
3. Mesosphere
Upper boundary: 80 – 85 km
Lower boundary: 50 km
The Mesosphere is the middle layer amongst all the layers. It is where the highest clouds can be found and where most meteors start to burn up when they enter the Earth’s atmosphere.
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