Thermosphere Definition
Thermosphere meaning is quite simple. The thermosphere is one of the layers of the earth's atmosphere that extends in an outward direction. It lies in between the mesosphere and exosphere layers of the atmosphere, the thermosphere layer is above the mesosphere and below the exosphere layer and it covers a major part of the Ionosphere, which is a part of the earth's atmosphere.
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About Thermosphere Layer in Detail
The altitude of the thermosphere layer begins from about 80kms above sea level and extends up to 700kms to space. The altitude makes the thermosphere enter the space and it’s a part of space too. In this layer the ultraviolet radiation causes photoionization of molecules, that is, ions are created in this layer of the atmosphere by the interaction of a photon with an atom or molecule. The thermosphere contributes majorly to the ionosphere of the earth's atmosphere, that is why photoionization or dissociation takes place in the thermosphere, as it lies in the ionosphere region.
Thermosphere and its Temperature
Here you will get to know about the thermosphere temperature range. The temperature of the upper thermosphere layer ranges from 500-degree Celsius to 2000-degree Celsius. It can even range higher than 2000- degree Celsius. Another fact of the temperature in the thermosphere layer is it can get 200 degrees Celsius higher in the daytime than at night. And it can get 500-degrees hotter than usual when the sun is very active. Thermosphere is the name derived from the language Greek, it means Heat. The temperature is always high in this layer of the temperature and the name is apt for the layer.
Air Present in the Thermosphere
The thermosphere is composed of air. The major components are atomic oxygen, atomic helium and atomic nitrogen. Here due to turbulence in the atmosphere, the different types of gas molecules are mixed together thoroughly.
In the thermosphere, there is an infrequent collision of gas particles that leads to the separation of gases according to the chemical elements the gas contains.
Much More Information About the Thermosphere
In this layer of atmosphere, the particles are electrically charged because of the radiation. It enables radio waves to be refracted and it can receive beyond the horizon. Much of X-ray and UV radiation from the sun is largely absorbed by the thermosphere when the sun is much active. When it absorbs this radiation the thermosphere expands due to heat and puffs up.
As the thermosphere is below the exosphere layer of the earth’s atmosphere, the exosphere begins at 600km from above sea level and extends into space. There is a Karman line that defines the boundary between the earth’s atmosphere and outer space, according to that thermosphere is a part of outer space. Because the exosphere begins in outer space that is from 600km above sea level, the thermosphere layer is extended to 700 km above sea levels, hence that makes the thermosphere a part of outer space.
As we know oceans have tides and waves, similarly, the earth's atmosphere including the thermosphere has tides and waves, which helps to move the energy along. This results in the production of electrical currents In some parts of the thermosphere.
The atmospheric pressure on the thermosphere is around the 0.0005 kPapressure level, there is a very minimal activity of air pressure at the top of the thermosphere.
Thermosphere and the Other Atmospheric Layers
Let’s understand the thermosphere atmosphere. The thermosphere is the fourth atmospheric layer which is above the mesosphere and below the exosphere. The thermosphere layer begins in the mesosphere region and ends in the exosphere region. But the atmospheric components don’t mix with the other. The transitional space between the mesosphere and thermosphere Is called mesopause. And between the thermosphere and exosphere, it's called thermopause. There is another important fact here, that is the Ionosphere, parts of the thermosphere, mesosphere, and exosphere is included in the ionosphere. There is an interdependence of thermosphere and ionosphere here, as the thermosphere is very hot, it ionizes the atoms in its layer, and produces an electric current.
The thermosphere layer is a thicker layer than other layers of the atmosphere, but not as thick as the exosphere. The thermosphere is home to the International Space Station as it orbits Earth, this is also where you'll find low Earth orbit satellites.
FAQs on Thermosphere
1. What is the thermosphere?
The thermosphere is the fourth layer of the Earth's atmosphere, located directly above the mesosphere and below the exosphere. It is characterised by extremely high temperatures, which increase with altitude due to the absorption of highly energetic solar radiation. Despite the heat, this layer is considered part of outer space and is where the International Space Station orbits the Earth.
2. At what altitude is the thermosphere located?
The thermosphere begins at an altitude of about 85 kilometres (53 miles) above the Earth's surface, just above the mesopause. It extends upward to the thermopause, which can be anywhere from 500 to 1,000 kilometres (310 to 620 miles) high. The exact height of the upper boundary varies significantly with solar activity.
3. Why is the thermosphere so hot, yet it would feel cold to a human?
The thermosphere reaches temperatures as high as 2,500°C (4,530°F) because its sparse gas molecules (like oxygen and nitrogen) absorb high-energy X-rays and ultraviolet radiation from the sun. However, it would feel freezing cold because temperature and heat are different. Temperature measures the speed of particles, while heat is the transfer of energy. The particles are so far apart in the near-vacuum of the thermosphere that they would not be able to transfer enough energy to a person or object to make it feel warm.
4. What is the relationship between the thermosphere and the ionosphere?
The ionosphere is not a separate layer but a region of the atmosphere that overlaps with the thermosphere. It is created when energetic solar radiation strikes the gas molecules in the thermosphere, knocking electrons loose and creating a shell of electrically charged particles (ions). This process, called ionisation, is most prominent in the thermosphere, making the two regions intrinsically linked.
5. How are the auroras (Northern and Southern Lights) formed in the thermosphere?
The auroras are a spectacular natural phenomenon that occurs in the thermosphere. They are created when charged particles from the sun, carried by the solar wind, are guided by Earth's magnetic field towards the poles. These particles then collide with gas atoms and molecules (primarily oxygen and nitrogen) in the thermosphere, exciting them and causing them to emit photons of light, which we see as the colourful, dancing auroras.
6. What is the importance of the thermosphere for Earth?
The thermosphere plays a crucial protective role for life on Earth. Its key importance includes:
Absorbing Harmful Radiation: It absorbs some of the most harmful solar radiation, such as X-rays and extreme ultraviolet (EUV) radiation, preventing them from reaching the surface.
Enabling Radio Communication: The ionised part of the thermosphere reflects and refracts radio waves, which is essential for long-distance radio communication.
Burning up Meteors: Many meteors and small space debris burn up in this layer due to friction with its particles, protecting the planet from impacts.
7. How does solar activity affect the size and density of the thermosphere?
The thermosphere's size and density are highly dependent on solar activity. During periods of high solar activity (like solar maximums), the sun emits more intense radiation, causing the thermosphere to heat up and expand significantly. This expansion increases its altitude and density, which in turn creates more atmospheric drag on satellites and the International Space Station, requiring them to adjust their orbits to avoid falling back to Earth.
8. Is the thermosphere the hottest layer of the atmosphere?
Yes, based on particle kinetic energy (temperature), the thermosphere is the hottest layer of Earth's atmosphere. Temperatures here can soar above 2,000°C. However, the exosphere, which lies above it, is sometimes considered hotter at its outermost edge, though the distinction is complex as the exosphere is essentially the fringe of space where atmospheric particles are extremely scarce.
