Thermosphere

Definition

The thermosphere is the layer of Earth's atmosphere located above the mesosphere and below the exosphere, characterized by a rapid increase in temperature with altitude. This layer contains a small amount of gas, but the gases present are highly energetic and can reach temperatures of up to 2,500°C or more, primarily due to the absorption of solar radiation. The thermosphere is also where the auroras occur and is crucial for radio communication due to its ionization effects.

5 Must Know Facts For Your Next Test

1. The thermosphere begins at an altitude of about 80 kilometers (50 miles) above Earth and extends to around 600 kilometers (370 miles).
2. Temperature in the thermosphere increases significantly with altitude because solar radiation is absorbed by the few gas molecules present.
3. This layer is responsible for the occurrence of the northern and southern lights (auroras) as charged particles from the sun interact with Earth's magnetic field.
4. The thermosphere plays a vital role in radio communication; signals can be reflected off the ionized layers within it, allowing for long-distance transmission.
5. Satellites orbiting Earth are typically found within or near the thermosphere, taking advantage of its lower atmospheric drag compared to lower layers.

Review Questions

• How does the temperature change within the thermosphere compared to other atmospheric layers, and what causes this change?
  • In the thermosphere, temperature increases with altitude, which is opposite to what happens in the troposphere and stratosphere where temperatures decrease. This increase is primarily caused by the absorption of intense solar radiation by a sparse number of gas molecules. As these molecules absorb energy from solar radiation, they become highly energetic, leading to significantly higher temperatures in this layer.
• Discuss the significance of the ionosphere within the thermosphere and its impact on communication technology.
  • The ionosphere is a crucial part of the thermosphere that contains a high concentration of ions and free electrons. Its ability to reflect radio waves makes it essential for long-distance communication, as it allows signals to travel beyond the horizon. Communication technologies rely on this property, especially for shortwave radio transmissions, which can bounce off the ionosphere to reach distant locations.
• Evaluate how human activities might influence conditions in the thermosphere and potential implications for satellite operations.
  • Human activities, particularly those that contribute to climate change and ozone depletion, may affect conditions in the thermosphere by altering atmospheric composition and energy absorption rates. Changes in temperatures can lead to variations in atmospheric density at altitudes where satellites operate. Increased drag on satellites due to lower atmospheric density could affect their orbits, operational lifespan, and communication systems reliant on stable conditions in this layer.

Related terms

ionosphere: A region within the thermosphere that contains a high concentration of ions and free electrons, allowing for the reflection of radio waves and contributing to radio communication.

exosphere:

The outermost layer of Earth's atmosphere, extending from the top of the thermosphere, where atmospheric particles are so sparse that they can travel hundreds of kilometers without colliding with one another.

mesosphere:

The layer of the atmosphere located below the thermosphere, characterized by decreasing temperatures with altitude and where most meteoroids burn up upon entering Earth's atmosphere.