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Why does temperature rise again in the thermosphere?

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Wispy cirrus clouds stretch across a bright blue sky above trees and a river at Pinawa Dam Provincial Park in Manitoba, Canada, with sunlight illuminating the scene. — Atmosphere The atmospheres of planets in the solar system are composed of various gases, particulates, and liquids. They are also dynamic places that redistribute heat and other forms of energy. On Earth, the atmosphere provides critical ingredients for living things. Here, feathery cirrus clouds drift across the deep blue sky over Pinawa Dam Provincial Park, near Pinawa, Manitoba, Canada.

The temperature in the thermosphere rises with increasing altitude primarily due to the absorption of high-energy solar ultraviolet radiation by atmospheric gases.1

Unlike the lower layers of the atmosphere, where temperature is largely influenced by heat from the Earth's surface or the ozone layer, the thermosphere is directly heated by the Sun. This solar radiation removes electrons from atmospheric gases, a process that creates the ionosphere and releases significant energy into the surrounding air. Because the density of the atmosphere is extremely low at these altitudes, this absorbed energy results in very high kinetic temperatures, which can range from 500 K to 2,000 K depending on the level of solar activity.2314