Fr.: minimum de Maunder
A period from about 1645 to 1715 when the number of → sunspots was unusually low. This → solar activity minimum is attested also through the increased content of carbon 14 in tree rings in that period. The reason is that the cosmic rays which produce 14C reach the Earth in a greater number when there is weak solar activity (see also → radiocarbon dating). The Maunder minimum occurred during a period of cooling of the Earth, called the → Little Ice Age. The Maunder minimum is one of a number of periods of low solar activity, including the → Dalton minimum, the → Sporer minimum, the → Wolf minimum, and the → Oort minimum.
After the British astronomer Edward Walter Maunder (1851-1928) who, along with Gustav Spörer of Germany, first called attention to this phenomenon; → minimum.