Thermosphere

Definition

The thermosphere is the layer of Earth's atmosphere that lies above the mesosphere and extends from about 85 kilometers (53 miles) to 600 kilometers (373 miles) above the Earth's surface. This layer is characterized by a dramatic increase in temperature with altitude, due to the absorption of high-energy solar radiation, making it one of the hottest layers in the atmosphere. The thermosphere is also where the auroras occur and where the ionosphere exists, which plays a crucial role in radio communication and satellite operations.

5 Must Know Facts For Your Next Test

1. Temperatures in the thermosphere can reach up to 2,500 degrees Celsius (4,500 degrees Fahrenheit) or more, but due to low air density, it would not feel hot to human skin.
2. The thermosphere plays a key role in atmospheric reentry for spacecraft, as it is where friction from air at high speeds generates significant heat.
3. Auroras, also known as the Northern and Southern Lights, occur in the thermosphere when charged particles from the sun collide with gases in this layer.
4. The thermosphere contains the ionosphere, which is crucial for long-distance radio communications because it reflects radio waves back to Earth.
5. This layer of atmosphere experiences extreme variations in temperature and density due to solar activity, including solar flares and coronal mass ejections.

Review Questions

• How does the temperature change with altitude in the thermosphere, and what causes this phenomenon?
  • In the thermosphere, temperature increases dramatically with altitude, reaching up to 2,500 degrees Celsius or more. This increase is primarily due to the absorption of high-energy solar radiation by atmospheric particles. Unlike other layers where temperature decreases with altitude, the unique composition and low density of air in the thermosphere allow for this unusual thermal behavior.
• Discuss the significance of the ionosphere within the thermosphere and its impact on communication technologies.
  • The ionosphere is a crucial part of the thermosphere that contains a high concentration of ions and free electrons. This layer influences radio wave propagation by reflecting certain frequencies back to Earth, enabling long-distance communication. Without the ionosphere's reflective properties, technologies such as AM radio and some forms of satellite communication would be significantly impaired.
• Evaluate how solar activity affects conditions in the thermosphere and discuss its implications for satellites orbiting Earth.
  • Solar activity, including solar flares and coronal mass ejections, can drastically affect conditions in the thermosphere. These events increase temperatures and densities within this layer, leading to fluctuations that can impact satellite orbits and operations. Satellites may experience increased drag due to higher densities, affecting their trajectories and operational lifespan. Understanding these interactions is critical for satellite mission planning and space weather forecasting.

Related terms

ionosphere: A region of the thermosphere that contains a high concentration of ions and free electrons, affecting radio wave propagation and enabling phenomena such as auroras.

mesosphere: The atmospheric layer located below the thermosphere, characterized by decreasing temperatures with altitude and where most meteoroids burn up upon entering the atmosphere.

solar radiation: Energy emitted by the sun, which is absorbed by the thermosphere, causing its temperature to rise significantly with altitude.