
1) Atmosphere of Earth 2) Layer
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https://www.crosswordclues.com/clue/thermosphere

The Earth atmosphere between 120 and 250 to 400 km (depending on the solar and geomagnetic activity levels), where temperature has an exponential increase up to a limiting value Texo at the thermopause. The temperature Texo is called the exospheric temperature.
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http://www.braeunig.us/space/glossary.htm

region of increasing temperature in Earth`s atmosphere that is located above the mesosphere. The base of the thermosphere (the mesopause) is at an ... [3 related articles]
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http://www.britannica.com/eb/a-z/t/37

An upper part of Earth`s atmosphere that includes the ionosphere and extends from an altitude of 85 km (above the mesopause), where the temperature is about -33 °C, to the lower level of the exosphere at 500 km, where the temperature is about 1,500 °C. The thermosphere is known be very activ...
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http://www.daviddarling.info/encyclopedia/T/thermosphere.html

that part of the Earth's atmosphere located above the mesosphere in which temperature increases and then remains constant with increasing height and from which there is virtually no further escape of particles to free space NOTE - The thermosphere extends to a height of 500 to 600 km.
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http://www.electropedia.org/iev/iev.nsf/display?openform&ievref=705-06-12

Outermost layer of the atmosphere, above the mesosphere.
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http://www.encyclo.co.uk/local/20130

Atmospheric layer above the mesosphere (above 80 kilometers) characterized by air temperatures rising rapidly with height. The thermosphere is the hottest layer in the atmosphere. In the thermosphere, gamma, X-ray, and specific wavelengths of ultraviolet radiation are absorbed by certain gases in the atmosphere. The absorbed radiation is then conve...
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http://www.physicalgeography.net/physgeoglos/t.html

[
n] - the atmospheric layer between the mesosphere and the exosphere
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http://www.webdictionary.co.uk/definition.php?query=thermosphere

thermosphere In meteorology, the atmospheric layer, constituting essentially all of the atmosphere above the mesosphere (that is, above about 80-90 km altitude), in which temperature increases with height; includes the exosphere and most or all of the ionosphere. In the area above the mesosphere, the temperature increases with altitude up to about ...
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http://www.wordinfo.info/words/index/info/view_unit/1999/7

The layer of the atmosphere lying between 100 - 400 km altitude. More information here.
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https://www.encyclo.co.uk/local/20751
noun the atmospheric layer between the mesosphere and the exosphere
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https://www.encyclo.co.uk/local/20974
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