The Thermosphere

The Earth's thermosphere is the layer of the atmosphere which is first exposed to the Sun's radiation and so is first heated by the Sun. The air is so thin that a small increase in energy can cause a large increase in temperature.

The temperature in the thermosphere is very dependent on solar activity. When the Sun is active, temperatures can reach up to 1,500°C or higher!

Because of the thin air in the thermosphere, scientists can't measure the temperature directly. They measure the density of the air by how much drag it puts on satellites and then use the density to find the temperature.

The thermosphere also includes the region of the Earth's atmosphere called the ionosphere. The ionosphere is the region of the atmosphere that is filled with charged particles. Elevated temperatures can sometimes cause a molecule to become ionized, therefore, the ionosphere and thermosphere can overlap.

This is an image of the space shuttle as it is orbiting around the Earth. The space shuttle orbits in the thermosphere of the Earth.
Click on image for full size (90K JPEG)
Image from: NASA

Last modified June 26, 2002 by the Windows Team

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