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The region of the atmosphere from 30 to 190 kilometers (20 to 120 miles) above the earth's surface, in which photochemical reactions initiated by solar radiation occur.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
(Physical Geography) meteorol a rare name for thermosphere
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
che•mo•sphere(ˈki məˌsfɪər, ˈkɛm ə-)
the region of the atmosphere most characterized by chemical, esp. photochemical, activity, starting in the stratosphere and including the mesosphere and perhaps part of the thermosphere.
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