Solar activity strongly influences temperature in the thermosphere.
The thermosphere is typically about 200°C hotter in the daytime than at night, and roughly 500°C hotter when the Sun is very active than at other times. Temperatures in the upper thermosphere can range from about 500°C to 2,000°C or higher.
Much of the X-ray and UV radiation from the Sun is absorbed in the thermosphere. The aurora (the Southern and Northern Lights) primarily occur in the thermosphere.
Air in the lower atmosphere is mainly composed of the familiar blend of about 80% nitrogen molecules (N2) and about 20% oxygen molecules (O2).