Tag: thermosphere

The thermosphere is a layer of Earth's atmosphere situated above the mesosphere and below the exosphere, extending approximately from 80 km to 550 km above Earth's surface. It is characterized by increasing temperatures rapidly with height, reaching up to 2,500 °C or more due to the absorption of high-energy solar radiation, particularly X-rays and Extreme Ultra-Violet (EUV) radiation, which can intensify during periods of solar activity. However, despite these extreme temperatures, the low density of gases in this region (nearly a vacuum) means there are very few air molecules to transfer heat. As a result, the high temperatures would not feel hot to humans. Temperature cannot be measured using an ordinary thermometer because the gases become very light due to their extremely low density. It contains a very low concentration of gases, primarily oxygen (O₂) and nitrogen (N₂). Ionosphere and radio communication Ionosphere : A significant portion of the thermosphere constitutes the ionosphere, a region filled with ionized particles formed when Extreme Ultraviolet (EUV) and X-ray solar radiation ionize atmospheric atoms and molecules. It plays a crucial role in radio communication by allowing shortwave radio waves to bounce off its layers. Its density varies with the 11-year solar cycle due to changes in EUV and X-ray photon flux. Structure and Layers : It is divided into distinct layers — the D, E, and F-layers—which result from differences in solar radiation and atmospheric composition. D, E and F ionospheric regions, including F1 and F2 in the daytime illustration; source image attribution: Encyclopaedia Britannica, Inc., 2012. The diagram labels D, E and F regions and shows F1 and F2 within the daytime F region. Quick revision Thermospheric temperature rises with height through absorption of high-energy solar radiation.Low gas density limits heat transfer despite high temperature.Solar EUV and X-ray radiation ionize atmospheric particles.The chapter identifies D, E and F ionospheric layers. Related concepts from Chapter 1Abiotic components of environmentPhotosynthesis and biotic–abiotic interactionsThe interdisciplinary nature of environmental scienceRelated topicsMesosphere: Noctilucent Clouds, Meteors and Gravity WavesAurora and Magnetosphere: Solar Wind and Earth’s Magnetic FieldSodium Layer: Artificial Guide Stars and Adaptive OpticsChapter 2 indexComposition of Atmosphere: Gases, Water Vapour and DustStructure of Atmosphere: Layers, Exosphere, Homosphere and HeterosphereTroposphere, Stratosphere and Polar VortexOzone: Formation, Depletion and Effects on PlantsMesosphere: Noctilucent Clouds, Meteors and Gravity WavesThermosphere and Ionosphere: Temperature and Radio CommunicationAurora and Magnetosphere: Solar Wind and Earth’s Magnetic FieldSodium Layer: Artificial Guide Stars and Adaptive Optics