the lowest region of the ionosphere, characterized by mounting electron and ion density: exists, during the day only, from about 43 to 50 miles (70 to 80 km) altitude.
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Compare D region.
Origin of D layer
First recorded in 1930–35
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Science definitions for d layer
See D region.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.