Mesosphere (English spelling)

Japanese: 中間圏 - ちゅうかんけん（英語表記）mesosphere

The atmospheric layer above the stratosphere and below the thermosphere. At an altitude of 50 to 80 km above the earth's surface, the atmospheric temperature ranges from about 270 K absolute at the bottom to about 200 K at the top, and decreases with increasing altitude. This is because, of the radiation from the sun, extreme ultraviolet rays, which are similar to X-rays, are absorbed in the thermosphere above, while longer-wavelength ultraviolet rays are absorbed in the dense air below the stratosphere, and ozone is produced more in the stratosphere than in the mesosphere, so there is little heating in this layer. Throughout the mesosphere, the composition of the atmosphere remains roughly the same as at sea level (there is no diffusion separation of heavy and light gases), and the pressure and density are reduced to 1/1,300 and 1/1,200, respectively, at an altitude of 50 km, and to 1/100,000 and 1/66,000, respectively, at an altitude of 80 km, compared to the values at sea level.

Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information

Japanese:

成層圏の上，熱圏の下にある大気層。地表からの高さ 50～80kmにわたり，大気温度は低部で絶対温度 270Kくらいから，上部で 200Kくらいまでで，高度が上がるにつれて低下していく。その理由は，太陽からの放射線のうち，X線に近い超紫外線は上方の熱圏で吸収されてしまい，波長の長い紫外線は空気の濃い下方の成層圏で吸収され，オゾンの生成も成層圏で多く中間圏では少ないなど，この層での加熱が少ないためである。中間圏を通じて，大気の組成は海面上とほぼ同じ比率を保ち（重い気体と軽い気体の拡散分離は起こっておらず），気圧および密度が海面上の値に比べ，高度 50kmで，それぞれ 1300分の1および 1200分の1，高度 80kmで 10万分の1および 6万6000分の1に低減する。

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