the lowest region of the ionosphere, in which the D layer develops.
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Lexical Investigations: Fiat
The origin of the word fiat in English is connected to the origin of the world itself. Taken from the Latin meaning “let it be done,” this word appears in the Latin translation of Genesis, the first book of the bible, when God proclaimed “let there be light” (fiat lux). As a result, many early uses of fiat were biblical allusions, as in John Donne’s …
Origin of D region
First recorded in 1925–30
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
the lowest region of the ionosphere, extending from a height of about 60 kilometres to about 90 kilometres: contains a low concentration of free electrons and reflects low-frequency radio wavesSee also ionosphere
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
The region of the atmosphere that lies in the upper mesosphere, extending from about 70 to 90 km (43 to 56 mi) above the Earth. The D region is responsible for the daytime absorption of high-frequency radio signals; at night, oxygen ions recombine with free electrons and form oxygen molecules that are transparent to such signals, which bounce off of the E region and back to Earth. Also called D layer Compare E region F region.
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