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

This form of lighting, known as a gigantic jet, is a type of discharge that occurs between thunderstorms and the Earth's ionosphere, 50 miles up, according to NASA. —Ross Rosenfeld, Newsweek, 26 Feb. 2025

The signals' refraction off the ionosphere allows the radar to see over the horizon, but the movement of the ionosphere introduces variations in the signal, as do reflections from the Earth's surface. —IEEE Spectrum, 24 June 2021

The most ancient 21 cm signal would arrive to us at wavelengths that are reflected off Earth’s ionosphere, notes Anastasia Fialkov, a cosmologist and astrophysicist at the Institute of Astronomy in Cambridge, England. —The Editors, JSTOR Daily, 30 Jan. 2025

Tonga’s pressure wave dispatched anomalous electric currents through the ionosphere. —Carly Miller, Forbes, 27 Sep. 2024

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The term was introduced by the British engineer and physicist Robert A. Watson-Watt (1892-1973), apparently first in an unpublished letter (November 8, 1926) to the secretary of the Radio Research Board, a government agency (see Nature, vol. 224, December 13, 1969, p. 1096).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