Definition of D region
: the lowest part of the ionosphere occurring approximately between 30 and 55 miles (50 and 90 kilometers) above the surface of the earth
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“D region.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/D%20region. Accessed 19 Aug. 2022.
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Time Traveler for D region
The first known use of D region was in 1930
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