ionosphere

noun

ion·​o·​sphere ī-ˈä-nə-ˌsfir 

: the part of the earth's atmosphere in which ionization of atmospheric gases affects the propagation of radio waves, which extends from about 30 miles (50 kilometers) to the exosphere, and which is contiguous with the upper portion of the mesosphere and the thermosphere

also : a comparable region of charged particles surrounding another celestial body (such as Venus)

ionospheric

ˌī-ˌä-nə-ˈsfir-ik 

-ˈsfer-

adjective

ionospherically

ˌī-ˌä-nə-ˈsfir-i-k(ə-)lē 

-ˈsfer-

adverb

Examples of ionosphere in a Sentence

Recent Examples on the Web

The Australian system, developed over 40 years, works by refracting high-frequency electromagnetic waves off the ionosphere to detect distant objects that are invisible to conventional radars because of Earth’s curvature. — Rod McGuirk, Los Angeles Times, 23 June 2026

The Australian system, developed over 40 years, works by refracting high-frequency electromagnetic waves off the ionosphere to detect distant objects that are invisible to conventional radars because of Earth's curvature. — ABC News, 22 June 2026

Subsequent studies showed that these storms can inject large numbers of high-energy electrons into the polar ionosphere, potentially disrupting communication and navigation technologies. — Rupendra Brahambhatt, Interesting Engineering, 21 June 2026

Another gap exists for radio waves with wavelengths of 10 meters or more, which are reflected by Earth’s ionosphere; to observe these, astronomers have proposed building radio telescopes on the moon’s far side. — Phil Plait, Scientific American, 15 May 2026

Word History

Etymology

ion or ion(ization) + -o- + -sphere

Note: The term was introduced by the British engineer and physicist Robert A. Watson-Watt (1892-1973), apparently first in an unpublished letter (November 8, 1926) to the secretary of the Radio Research Board, a government agency (see Nature, vol. 224, December 13, 1969, p. 1096). Watson-Watt used it in print in the Quarterly Journal of the Royal Meteorological Society, vol. 55 (1929), p. 278.

First Known Use

1926, in the meaning defined above

Kids Definition

ionosphere

noun

ion·​o·​sphere ī-ˈän-ə-ˌsfi(ə)r 

: the part of the earth's atmosphere beginning at an altitude of about 30 miles (50 kilometers) and extending outward that contains free electrically charged particles

ionospheric

ī-ˌän-ə-ˈsfi(ə)r-ik 

-ˈsfer-

adjective