Plain English Meaning

A high layer of the atmosphere where the sun's energy strips electrons off air molecules, leaving them electrically charged. Because of this, it can bounce radio signals back to Earth, which is why radio waves can travel long distances.

Full Definition

A layer of the upper atmosphere, extending from roughly 50 to 400 miles above the Earth's surface, in which solar radiation ionizes gas molecules, creating electrically charged particles. This ionization allows the layer to reflect and refract certain radio waves, making long-distance radio communication possible.

Context Anchor

Seen in atmosphere and radio communication discussions, especially when learning why some radio signals travel farther or change strength at certain times.

Derivation

From '' (an electrically charged particle) plus '' (a layer surrounding the Earth). The name comes directly from what defines this layer: it is the region full of ions.