411 REFERENCE · Wiktionary
D region
Reference material by Wiktionary contributors. This retains its source identity and is not 411 news reporting.
English
Alternative forms
en D-region
Etymology
en
Proper noun
D region 1
The innermost layer of the ionosphere, located 48 km (30 mi) to 90 km (56 mi) above the surface of the Earth.
Synonyms
D layer
Further reading
en Atmosphere