The Astronautics Vocabulary is a glossary of terms that pertain to the science and technology of spaceflight. This alphabetical list can be navigated by clicking on the letters A-Z displayed on this page.
Definition: The collective term for various layers of ionized particles and electrons found at altitudes of 80-250 km in the atmosphere. The principal regions are the D layer, E layer and F layer. Ionization is caused primarily by short-wavelength (X-ray and ultraviolet) solar radiation during the daytime.