ion·​o·​sphere ī-ˈä-nə-ˌsfir How to pronounce ionosphere (audio)
: 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 adjective
ionospherically adverb

Examples of ionosphere in a Sentence

Recent Examples on the Web Solar radiation impacts Earth’s ionosphere, a layer in the upper atmosphere, causing fluctuations that can interfere with radio transmissions from satellites passing through this layer. Passant Rabie / Gizmodo, Quartz, 13 May 2024 Moreover, the anomalies from the storm are constantly shifting through the ionosphere like ripples in a pool. Geoff Brumfiel, NPR, 10 May 2024 The radiation caused a sudden disturbance to the Earth’s ionosphere, even though the source was an explosion nearly 2 billion light years away. Chris Impey, Discover Magazine, 8 Apr. 2024 In reality, a solar eclipse brings a temporary sharp drop in solar radiation — an event that ham radio operators have been eagerly anticipating for months, with competitions and experiments looking to fill the Earth's suddenly radiation-free ionosphere with radio signals. Bill Chappell, NPR, 8 Apr. 2024 During the 2023 annular eclipse, instruments on the rockets measured sharp, immediate changes in the ionosphere. Ashley Strickland, CNN, 3 Apr. 2024 Scientists know the ionosphere evolves in a 24-hour process, from day to night, says Frissell. Catherine Duncan, Smithsonian Magazine, 18 Mar. 2024 By measuring the strength of those signals information about the height, density and dynamics of the ionosphere can be collected. Elizabeth Weise, USA TODAY, 31 Mar. 2024 The data will inform how the ionosphere behaves when the sun is blocked, in comparison to before and after the eclipse. Catherine Duncan, Smithsonian Magazine, 18 Mar. 2024

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'ionosphere.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


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term was introduced by the British engineer and physicist Robert A. Watson-Watt (1892-1973), apparently first in an unpublished letter (November 8, 1926) to the secretary of the Radio Research Board, a government agency (see Nature, vol. 224, December 13, 1969, p. 1096).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

Time Traveler
The first known use of ionosphere was in 1926

Dictionary Entries Near ionosphere

Cite this Entry

“Ionosphere.” Dictionary, Merriam-Webster, Accessed 28 May. 2024.

Kids Definition


ion·​o·​sphere ī-ˈän-ə-ˌsfi(ə)r How to pronounce ionosphere (audio)
: 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 adjective

More from Merriam-Webster on ionosphere

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