D region

D region

n.

See D layer.

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D region

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 regionF region

Thesaurus

Noun

1.

D region - the lowest region of the ionosphere (35 to 50 miles up) that reflects low-frequency radio waves D-layer ionosphere - the outer region of the Earth's atmosphere; contains a high concentration of free electrons