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[thur-muh-sfeer] /ˈθɜr məˌsfɪər/
the region of the upper atmosphere in which temperature increases continuously with altitude, encompassing essentially all of the atmosphere above the mesosphere.
1950-55; thermo- + sphere Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for thermosphere
  • The upper limit of the thermosphere is referred to as the exosphere.
British Dictionary definitions for thermosphere


an atmospheric layer lying between the mesosphere and the exosphere, reaching an altitude of about 400 kilometres where the temperature is over 1000°C
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
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Word Origin and History for thermosphere

1924, from thermo- + sphere.

Online Etymology Dictionary, © 2010 Douglas Harper
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thermosphere in Science
The region of the Earth's upper atmosphere lying above the mesosphere and extending from a height of approximately 80 km (50 mi) to between 550 and 700 km (341 and 434 mi) above the Earth's surface. In the thermosphere temperatures increase steadily with altitude, reaching as high as 1,727°C (3,140°F) at the highest elevations. Chemical reactions occur much faster here than on the surface of the Earth. See also exosphere, mesosphere, stratosphere, troposphere., See illustration at atmosphere.

The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Article for thermosphere

region of increasing temperature in Earth's atmosphere that is located above the mesosphere. The base of the thermosphere (the mesopause) is at an altitude of about 80 km (50 miles), whereas its top (the thermopause) is at about 450 km.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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