Ｄ層でぃーそう

noun

D layer; D region

Technical term in atmospheric physics; refers to the lowest region of the ionosphere, existing only during daylight hours.

• Ｄ層そうは昼ひる間まだけ存そん在ざいする電でん離り層そうの一いち部ぶです。

  The D layer is a part of the ionosphere that exists only during the daytime.