The thermosphere is the layer of the Earth atmosphere that is closest to space, and is where many satellites and spacecraft operate.

Thermosphere Definition:

he thermosphere is the layer of Earth’s atmosphere that lies above the mesosphere and extends from about 80 kilometers (50 miles) to the edge of space, which is around 500-1000 kilometers (310-620 miles) above the Earth’s surface. The exact boundary between the thermosphere and the outermost layer of the atmosphere, the exosphere, is not clearly defined as the density of the atmosphere gradually decreases with altitude.

Thermosphere Composition:

The thermosphere is composed mainly of molecular nitrogen (N2) and atomic oxygen (O), as well as smaller amounts of other gases such as helium (He), hydrogen (H), and carbon dioxide (CO2). The concentration of these gases is extremely low, with a total density of only about 10-11 kg/m3 at the lower thermosphere and decreasing rapidly with altitude.

Thermosphere Temperature:

The temperature of the thermosphere can reach as high as 2,500°C (4,500°F), although this temperature does not correspond to the sensation of heat due to the extremely low density of the gases. This high temperature is caused by the absorption of high-energy solar radiation by the thermosphere’s gases.

Thermosphere Altitude:

The thermosphere starts at an altitude of about 80 km (50 miles) and extends up to about 690 km (430 miles) above the Earth’s surface. The upper boundary of the thermosphere is not well-defined, as the gases gradually become more diffuse and merge with the rarefied gas in the exosphere.

Thermosphere Key Characteristics:

The thermosphere is characterized by high temperatures due to the absorption of solar radiation, but the density of the gases is extremely low, making it difficult for the heat to transfer to objects.

The ionosphere, which is a region of the atmosphere that is electrically charged due to the presence of ions and free electrons, is located within the thermosphere.

The thermosphere is also the layer of the atmosphere where the auroras occur, which are beautiful natural displays of light caused by the interaction between the Earth’s magnetic field and the solar wind.