Thermosphere

The atmospheric layer above the mesosphere, where temperatures rise sharply with altitude as sparse gases absorb high-energy solar radiation.

Extreme ultraviolet radiation: Solar electromagnetic radiation with wavelengths shorter than ultraviolet light, absorbed high in Earth’s atmosphere. Its absorption by sparse gases supplies much of the thermosphere’s heat.
Earth's atmosphere: The envelope of gases held around Earth by gravity. The thermosphere is one of its major layers.
Atmospheric drag: The resistive force exerted on a moving object by gas in an atmosphere. Even thin thermospheric gas slows low-orbit satellites, especially during solar storms.
Troposphere: The lowest atmospheric layer, where most weather occurs and temperature generally decreases with altitude. Its usual lapse rate contrasts with the thermosphere’s rising temperature.
X-ray: High-energy electromagnetic radiation with wavelengths shorter than ultraviolet light. Solar X-rays deposit energy in the upper thermosphere and help ionize its gases.
Mesosphere: The atmospheric layer above the stratosphere and below the thermosphere. Its upper boundary marks the thermosphere’s lower boundary.
Low Earth orbit: An Earth-centered orbit at relatively low altitude, typically below about 2,000 kilometers. Its satellites pass through the thermosphere and experience variable drag.
Stratosphere: The atmospheric layer above the troposphere, where ozone absorption causes temperature to rise with altitude. It also warms upward, but through ozone absorption rather than the thermosphere’s high-energy radiation.
Thermospheric temperature: A measure of the average kinetic energy of particles in the thermosphere. It rises with altitude even though the thin gas transfers little heat to objects.
Stratopause: The boundary between the stratosphere and the mesosphere. It helps locate the layers below the thermosphere in the atmospheric sequence.

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