This is a region of Earth’s upper atmosphere. It spans the area between 75 and 1,000 kilometers (47 and 620 miles) above the planet’s surface. The layer grows and shrinks in response to radiation from the sun. It also absorbs some of that radiation — the type called extreme ultraviolet light. In the ionosphere, ultraviolet light strips electrons from the atoms they are usually bound to. The process is called ionization. That’s how the ionosphere gets its name. And it results in an ionosphere that is full of electrically charged particles.
The ionosphere is useful in many ways. It protects organisms on Earth by absorbing those harmful extreme ultraviolet rays. The electrically charged particles in the ionosphere also reflect some of the waves coming from Earth. In particular, the ionosphere reflects radio waves. It bounces them back toward the ground. This lets radio-users use the ionosphere to send signal long distances, even to the other side of Earth!
In a sentence
Scientists used the August 21, 2016 eclipse to investigate how the ionosphere changes at night.