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Solar minimum is the regular period of least solar activity in the Sun's 11-year solar cycle. During solar minimum, sunspot and solar flare activity diminishes, and often does not occur for days at a time. On average, the solar cycle takes about 11 years to go from one solar minimum to the next, with duration observed varying from 9 to 14 years.
The Dalton minimum in the 400-year history of sunspot numbers. The Dalton Minimum was a period of low sunspot count, representing low solar activity, named after the English meteorologist John Dalton, lasting from about 1790 to 1830 [1] or 1796 to 1820, [2] corresponding to the period solar cycle 4 to solar cycle 7.
The Maunder Minimum shown in a 400-year history of sunspot numbers. The Maunder Minimum, also known as the "prolonged sunspot minimum", was a period around 1645 to 1715 during which sunspots became exceedingly rare. During the 28-year period 1672–1699 within the minimum, observations revealed fewer than 50 sunspots.
Solar Cycles Start (Maximum) Spotless days [10] Solar cycle 10–11 1860 – Feb 406 Solar cycle 11–12 1870 – Aug 1028 Solar cycle 12–13 1883 – Dec 736 Solar cycle 13–14 1894 – Jan 934 Solar cycle 14–15 1906 – Feb 1023 Solar cycle 15–16 1917 – Aug 534 Solar cycle 16–17 1928 – Apr 568 Solar cycle 17–18 1937 – Apr 269
Solar irradiance varies systematically over the cycle, [69] both in total irradiance and in its relative components (UV vs visible and other frequencies). The solar luminosity is an estimated 0.07 percent brighter during the mid-cycle solar maximum than the terminal solar minimum.
The Spörer Minimum is a hypothesized 90-year span of low solar activity, from about 1460 until 1550, which was identified and named by John A. Eddy in a landmark 1976 paper published in Science titled "The Maunder Minimum". [1]
The Homeric Minimum is a persistent and deep [1] grand solar minimum between about 800 and 600 BC. Cosmogenic beryllium-10 deposits in varves in a German lake show a sharp increase "2,759 ± 39 varve years before present", [2] [3] while carbon-14 is high starting around 830 BC. [4]
Solar cycle 24 is the most recently completed solar cycle, the 24th since 1755, when extensive recording of solar sunspot activity began. [ 1 ] [ 2 ] It began in December 2008 with a minimum smoothed sunspot number of 2.2, [ 3 ] [ failed verification ] and ended in December 2019. [ 4 ]