D region

American  

noun

1. the lowest region of the ionosphere, in which the D layer develops.

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D region British  

noun

1. 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 waves See also ionosphere

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D region Scientific  

1. 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.

2. Also called D layer

3. Compare E region F region

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Etymology

Origin of D region

First recorded in 1925–30

Example Sentences

Ignoring or giving short shrift to the principles of open government is not infrequent - in The T&D; Region, around the state and throughout our country.

From Washington Times

Bradford pear trees are putting on a show in the Garden City and around the T&D; Region with their bounty of white flowers.

From Washington Times

Most recently, the water system received a $10 million grant to further expand its services to rural areas in and around The T&D; Region.

From Washington Times

This year, The T&D; Region saw minimal impact from hurricanes but was affected by wind and rain from a number of the storms that came ashore far away and turned east.

From Washington Times

A key to evacuation is opening up major routes to get people away from the coast to inland areas in The T&D; Region and beyond.

From Washington Times