List of solar cycles
This article's factual accuracy may be compromised due to out-of-date information. (August 2016)
The following is a list of solar cycles (sometimes called sunspot cycles), tracked since 1755 following the original numbering proposed by Rudolf Wolf in the mid-19th century The source data are the revised International Sunspot Numbers (ISN v2.0), as available at SILSO. Sunspot number counts exist since 1610 but the cycle numbering is not well defined during the Maunder minimum. It was proposed that one cycle might have been lost in the late 18th century, but this still remains not fully confirmed.
The smoothing was done using the traditional SIDC smoothing formula. Other smoothing formulas exist, and they usually give slightly different values for the amplitude and timings of the solar cycles. An example is the Meeus smoothing formula, with related solar cycles characteristics available in this STCE news item.
In the table below, the number of spotless days is the number between the maximum of the previous solar cycle and the maximum of the new solar cycle. As an example, there were 817 spotless days during the transit from solar cycle 23 to solar cycle 24.
The smoothed minimum ending cycle 24 is likely to be significantly higher than the one which ended cycle 23, making a Maunder-like minimum unlikely in the near future.
|Solar Cycle||Start||Smoothed minimum ISN||Maximum||Smoothed maximum ISN||Time of Rise (years)||Duration (years)||Spotless days|
|Solar cycle 1||1755 February||14.0||1761 June||144.1||6.3||11.3|
|Solar cycle 2||1766 June||18.6||1769 September||193.0||3.3||9.0|
|Solar cycle 3||1775 June||12.0||1778 May||264.3||2.9||9.3|
|Solar cycle 4||1784 September||15.9||1788 February||235.3||3.4||13.6|
|Solar cycle 5||1798 April||5.3||1805 February||82.0||6.8||12.3|
|Solar cycle 6||1810 August||0.0||1816 May||81.2||5.8||12.8|
|Solar cycle 7||1823 May||0.2||1829 November||119.2||6.5||10.5|
|Solar cycle 8||1833 November||12.2||1837 March||244.9||3.3||9.7|
|Solar cycle 9||1843 July||17.6||1848 February||219.9||4.6||12.4|
|Solar cycle 10||1855 December||6.0||1860 February||186.2||4.2||11.3||655|
|Solar cycle 11||1867 March||9.9||1870 August||234.0||3.4||11.8||406|
|Solar cycle 12||1878 December||3.7||1883 December||124.4||5.0||11.3||1028|
|Solar cycle 13||1890 March||8.3||1894 January||146.5||3.8||11.8||736|
|Solar cycle 14||1902 January||4.5||1906 February||107.1||4.1||11.5||934|
|Solar cycle 15||1913 July||2.5||1917 August||175.7||4.1||10.1||1023|
|Solar cycle 16||1923 August||9.4||1928 April||130.2||4.7||10.1||534|
|Solar cycle 17||1933 September||5.8||1937 April||198.6||3.6||10.4||568|
|Solar cycle 18||1944 February||12.9||1947 May||218.7||3.3||10.2||269|
|Solar cycle 19||1954 April||5.1||1958 March||285.0||3.9||10.5||446|
|Solar cycle 20||1964 October||14.3||1968 November||156.6||4.1||11.4||227|
|Solar cycle 21||1976 March||17.8||1979 December||232.9||3.8||10.5||272|
|Solar cycle 22||1986 September||13.5||1989 November||212.5||3.2||9.9||273|
|Solar cycle 23||1996 August||11.2||2001 November||180.3||5.3||12.3||309|
|Solar cycle 24||2008 December||2.2||2014 April||116.4||5.3||In progress||817|
|Solar cycle 25||First spot||(6.6 as of Apr 2019)||401|
- Kane, R.P. (2002). "Some Implications Using the Group Sunspot Number Reconstruction". Solar Physics 205(2), 383-401.
- "Did You Say the Sun Has Spots?". Space Today Online.
- "Sunspot numbers". WDC-SILSO. Royal Observatory of Belgium. Retrieved 19 May 2017.
- Hathaway,, D. (2015). "The solar cycle". Living Reviews in Solar Physics. 12: 4. arXiv:1502.07020. Bibcode:2015LRSP...12....4H. doi:10.1007/lrsp-2015-4.
- Usoskin; Mursula; Kovaltsov. "Heliospheric modulation of cosmic rays and solar activity during the Maunder minimum". J. Geophys. Res. 106(A8): 16039. Bibcode:2001JGR...10616039U. doi:10.1029/2000JA000105.
- Usoskin; et al. "A solar cycle lost in 1793-1800: Early sunspot observations resolve the old mystery". Astrophys. J. Lett. 700: L154. arXiv:0907.0063. Bibcode:2009ApJ...700L.154U. doi:10.1088/0004-637X/700/2/L154.
- "SIDC smoothing formula". WDC-SILSO. Royal Observatory of Belgium. Retrieved 19 May 2017.
- Meeus, J. (1958). "Une formule d'adoucissement pour l'activité solaire". Ciel et Terre. 74: 445. Bibcode:1958C&T....74..445M.
- "The solar cycle's new clothes". STCE. Royal Observatory of Belgium. Retrieved 8 July 2015.
- "Spotless Days". SpaceWeather.com. Retrieved 29 July 2014.
- "What's Wrong with the Sun?". NASA Science. NASA. Retrieved 29 July 2014.
- "Spotless Days Page". SILSO. Royal Observatory of Belgium. Retrieved 3 April 2017.
- "The first sunspot of cycle 25 is seen!". STCE. Royal Observatory of Belgium. Retrieved 22 December 2016.