The exobase is the outermost layer of the Earth's atmosphere, consisting of a thin layer of gas and plasma molecules. Some synonyms for the word exobase include the thermosphere, the outer atmosphere, and the upper atmosphere. The thermosphere, specifically, is a layer of the Earth's atmospheric envelope that is located above the mesosphere and below the exosphere. This layer is characterized by the presence of extremely high temperatures, which can reach up to 2000 degrees Celsius due to the absorption of solar radiation. The high temperatures cause the molecules in the thermosphere to become ionized, forming a layer of plasma that is used for various radio communications and satellite operations.