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By: Tabitha Mishra
| Last updated: February 12, 2017

What Does Thermosphere Mean?

The thermosphere is the layer of atmosphere between the earth’s exosphere and its mesosphere.

The thermosphere begins approximately 56 miles (90 km) above the earth’s surface and extends to a height of between 311 and 621 miles (500 to 1000 km) above the earth’s surface. It is the second-highest layer of the earth’s atmosphere where temperatures reach their maximum values and are highly variable in response to the level of solar activity.

Safeopedia Explains Thermosphere

The earth’s atmosphere is a mass of air that surrounds the earth and consists of a mixture of nitrogen (~78%), oxygen (~21%), and other gases (~1%). The atmosphere has several layers, each with unique characteristics and compositions. Beginning from the one closest to the planet's surface, the layers of the earth’s atmosphere are:

  • Troposphere
  • Stratosphere
  • Mesosphere
  • Thermosphere
  • Exosphere

Characteristics of the Thermosphere

The most common gases in the lower and middle portion of the thermosphere are oxygen and nitrogen. The upper thermosphere mainly contains atomic oxygen due to photodissociation and molecular diffusion at high altitudes.

The temperatures of the gases in the thermosphere fluctuate by up to 360°F between day and night. The temperatures are extremely high during the day, reaching up to 4,500°F in the upper portion of the thermosphere, down to 932°F closer to earth.

Despite these high temperatures, the thermosphere would actually feel cold since there are not enough gas molecules present to transfer the heat. This also prevents sound waves from traveling.

The Importance of the Thermosphere

The lower thermosphere also contains the ionosphere, which is a region that is ionized by solar radiation and is responsible for auroras. The ionosphere increases in thickness and moves closer to the earth during daylight, and rises at night allowing a greater range to certain frequencies of radio communication.

The ionosphere contains charged ions that reflect the radio waves transmitted by radio stations and communication centers, making them very crucial in wireless communication and broadcasting. The thermosphere also houses the International Space Station (ISS) as it orbits the earth and other low earth orbit satellites.

The magnetic Van-Allen belts that surround the ionosphere scatter cosmic radiation and much of the X-ray and UV radiation is absorbed in the thermosphere.


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