Thermosphere
Topic: Atmosphere: Composition, Structure and Elements of Weather · NCERT: Class 9, Ch 3 "Atmosphere and Climate"; Class 11, Ch 7 "Composition and Structure of Atmosphere"
Meaning
The thermosphere is the layer above the mesopause. Class 9 gives it as about 80 km to 700 km. Temperature rises sharply with height here, because the very thin gas absorbs X-rays and short-wave UV rays from the Sun. It contains the ionosphere (about 80–400 km), a zone of electrically charged particles called ions. The ionosphere reflects radio waves back to the Earth, which makes long-distance short-wave radio possible. Auroras also form in this layer.
Example
The International Space Station orbits at about 400 km, inside the thermosphere. During the May 2024 solar storm, this layer was disturbed. Radio and GPS signals were upset, and an aurora was seen as far south as Hanle in Ladakh.
Don't confuse with
- Ionosphere: it is a part of the thermosphere, defined by its charged particles. The thermosphere is the whole layer, defined by its rising temperature.