ionosphere

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Ionized layer of Earth's outer atmosphere (60–1,000 km/38–620 mi) that contains sufficient free electrons to modify the way in which radio waves are propagated, for instance by reflecting them back to Earth. The ionosphere is thought to be produced by absorption of the Sun's ultraviolet radiation. The British Antarctic Survey estimates that the ionosphere is decreasing at a rate of 1 km/0.6 mi every five years, based on an analysis of data from 1960 to 1998. Global warming is the probable cause.

The colours are derived from the state coat of arms of 1364. The Scandinavian cross is taken from the Danish flag. Effective date: 22 June 1906. >>