D layer


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Related to D layer: Gutenberg Discontinuity

D layer

[′dē ‚lā·ər]
(geology)
The lower mantle of the earth, between a depth of 600 and 1800 miles (1000 and 2900 kilometers).
(geophysics)
The lowest layer of ionized air above the earth, occurring in the D region only in the daytime hemisphere; reflects frequencies below about 50 kilohertz and partially absorbs higher-frequency waves.

D layer

D layerclick for a larger image
A part of the ionosphere. It is a region of increasing electron and ion density, which exists primarily during the day. It merges with the bottom layers of the E layer. Its average height lies between 50 and 100 km (30 and 60 miles), and it reflects frequencies below about 50 kHz.