termosfere

Termosfere, also known as the thermosphere, is a major layer of Earth's atmosphere situated above the mesosphere and below the exosphere. It generally starts around 80–100 kilometers above the surface and extends upward to roughly 500–1,000 kilometers, though the upper limit varies with solar activity and atmospheric conditions.

The thermosphere is characterized by extremely low air density. Temperature increases with altitude because this layer absorbs high-energy ultraviolet and X-ray radiation from the Sun, heating the few gas molecules that remain. At times of strong solar activity, temperatures can reach thousands of degrees Celsius, but the thin air means it would not feel hot to a human skin contact.

Gas composition in the thermosphere is mainly nitrogen (N2) and oxygen (O2) at lower altitudes, with a growing share of atomic oxygen (O), helium, and hydrogen at higher levels. A significant portion of the layer is ionized, forming the ionosphere, which contains ions such as O+, N2+, and NO+. This ionization enables radio wave propagation and affects satellite communication and navigation systems.

Key phenomena associated with the thermosphere include auroras, produced by charged solar particles interacting with Earth's magnetic field. The region also hosts many human activities in near-Earth space: the International Space Station orbits within this layer, and satellites experience atmospheric drag that can alter their orbits.

Variations in solar activity cause substantial changes in density and temperature within the thermosphere. It expands during solar maximum and contracts during solar minimum, influencing satellite lifetime, communications, and space weather conditions.