D-layer

from WordNet (r) 3.0 (2006)

D-layer
    n 1: the lowest region of the ionosphere (35 to 50 miles up)
         that reflects low-frequency radio waves [syn: {D-layer}, {D
         region}]

from The Collaborative International Dictionary of English v.0.48

D-layer \D-layer\ n.
   the lowest region of the ionosphere (35 to 50 miles up) that
   reflects low-frequency radio waves.

   Syn: D region.
        [WordNet 1.5]

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