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Following is a comparison of the growth of cycle 25 versus cycle 24, using the 13-month sunspot averages, beginning with the months of the respective minimums. Numbers in brackets for cycle 25 indicate the minimum possible value for that month, assuming there are no more sunspots between now (Jan 3, 2024) and six months after the end of the ...
One historical long-term correlation between solar activity and climate change is the 1645–1715 Maunder minimum, a period of little or no sunspot activity which partially overlapped the "Little Ice Age" during which cold weather prevailed in Europe. The Little Ice Age encompassed roughly the 16th to the 19th centuries.
Solar cycle 23 lasted 11.6 years, beginning in May 1996 and ending in January 2008. The maximum smoothed sunspot number (monthly number of sunspots averaged over a twelve-month period) observed during the solar cycle was 120.8 (March 2000), and the minimum was 1.7. [29] A total of 805 days had no sunspots during this cycle. [30] [31] [32]
Individual sunspots or groups of sunspots may last anywhere from a few days to a few months, but eventually decay. Sunspots expand and contract as they move across the surface of the Sun, with diameters ranging from 16 km (10 mi) [3] to 160,000 km (100,000 mi). [4] Larger sunspots can be visible from Earth without the aid of a telescope. [5]
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.
Many solar phenomena change periodically over an average interval of about 11 years. This solar cycle affects solar irradiation and influences space weather, terrestrial weather , and climate . The solar cycle also modulates the flux of short-wavelength solar radiation, from ultraviolet to X-ray and influences the frequency of solar flares ...
The date of the minimum is described by a smoothed average over 12 months of sunspot activity, so identifying the date of the solar minimum usually can only happen 6 months after the minimum takes place. Solar minimum is contrasted with the solar maximum, when hundreds of sunspots may occur.
Solar variation can be quantified using sunspot counts, but this measure is only reliable for periods after records of sunspot observations were routinely made by western astronomers. For periods before sunspot records, solar activity can be found from proxy methods, most notably the production of radioisotopes in the Earth's atmosphere from ...