Ionosphere

The region of Earth's atmosphere that extends from about 50 to 300 miles above the surface of the planet and is made up of multiple layers dominated by electrically charged, or ionized, atoms.

A complex atmospheric zone of ionized gases that extends between 50 and 400 miles (80 to 640 kilometers) above the earth's surface. It is located between the mesosphere and the exosphere and is included as part of the thermosphere.

The region of the atmosphere, extending from roughly 70 to 500 kilometers altitude, in which ions and free electrons exist in sufficient quantities to reflect electromagnetic waves.

That part of the atmosphere, extending from about 70 to 500 kilometers, in which ions and free electrons exist in sufficient quantities to reflect and/or refract electromagnetic waves. [After JP1]