American Meteorological Society Certification (AMS) Practice

The ionosphere is located within the thermosphere, which is the atmospheric layer that extends from approximately 85 kilometers (53 miles) to 600 kilometers (373 miles) above Earth's surface. This region is characterized by high temperatures resulting from the absorption of solar radiation, which can cause gas particles to become ionized. The ionosphere plays a critical role in radio wave propagation and is essential for various communication and navigation systems due to its ability to reflect certain radio frequencies back to Earth.

The other atmospheric layers, such as the stratosphere, troposphere, and mesosphere, occupy different regions of the atmosphere and do not contain the ionosphere. The stratosphere lies below the thermosphere and includes the ozone layer. The troposphere is the lowest layer where all weather occurs, and the mesosphere sits above the stratosphere but below the thermosphere. Hence, these layers do not possess the characteristics or region necessary for the formation of the ionosphere.