Definitions

from The American Heritage® Dictionary of the English Language, 5th Edition.

  • noun A region of the earth's atmosphere where ionization caused by incoming solar radiation affects the transmission of radio waves. It extends from a height of 70 kilometers (43 miles) to 400 kilometers (250 miles) above the surface.

from the GNU version of the Collaborative International Dictionary of English.

  • noun the outer region of the earth's atmosphere, beyond which is the exosphere; it contains a high concentration of free electrons and ions, and extends from about 50 miles to about 250 miles above the earth's surface, but the height shows daily and seasonal variation, and the composition of the particles in the ionosphere is also affected by events such as solar flares.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • noun The part of the Earth's atmosphere beginning at an altitude of about 50 kilometers (31 miles) and extending outward 500 kilometers (310 miles) or more.
  • noun The similar region of the atmosphere of another planet.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • noun the outer region of the Earth's atmosphere; contains a high concentration of free electrons

Etymologies

from Wiktionary, Creative Commons Attribution/Share-Alike License

iono- + -sphere

Examples

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