Il minimo di Maunder è il nome dato al periodo che va circa dal 1645 al 1715 dopo Cristo, quando le macchie solari divennero estremamente rare, come notato dagli astronomi del tempo. È così chiamato dal nome dell'astronomo solare E.W. Maunder, che visse più tardi, il quale scoprì la mancanza di macchie solari in quel periodo studiando le cronache dell'epoca. Per esempio, durante un periodo di 30 anni durante il minimo di Maunder, gli astronomi osservarono solamente about 50 spots instead of the usual 40,000 or 50,000.
The beginning of the Maunder Minimum was sudden and took place in a few years, with no precursor, rather than during its final phase, between 1700 and 1712, solar activity resumed gradually to increase [1].
The Maunder Minimum coincided with the middle and cooler than the so-called Little Ice Age during which Europe and North America, and perhaps the rest of the world (for which there are no reliable data) suffered winters extremely cold [2].
recently published data suggest that during the Maunder Minimum, the Sun and expanded its rotation slowed. It is assumed that a larger and slower Sun rotation is also a cooler Sun that provides less heat to Earth (the reason for the expansion and contraction of the Sun is not yet known, but may be the normal activity cycle similar to the eleven-year solar cycle, only much longer).
A cause-effect relationship between low sunspot activity and cold winters is still under discussion. Some scientists believe that solar activity affects climate change as carbon dioxide (see global warming). Recently, new studies have actually shown a correlation between sunspots (and thus activity of the sun) with a changing climate.
source
http://it.wikipedia.org/wiki/Minimo_di_Maunder
