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List of solar cycles

From Wikipedia, the free encyclopedia
(Redirected from List of Solar Cycles)

Solar cycles are nearly periodic 11-year changes in the Sun's activity that are based on the number of sunspots present on the Sun's surface. The first solar cycle conventionally is said to have started in 1755. The source data are the revised International Sunspot Numbers (ISN v2.0), as available at SILSO.[1] Sunspot counts exist since 1610[2] but the cycle numbering is not well defined during the Maunder minimum.[3] It was proposed that one cycle might have been lost in the late 18th century,[4] but this remains not fully confirmed.

Solar cycles can be reconstructed indirectly, using the radiocarbon 14C proxy, for the last millennium.[5]

The smoothing is done using the traditional SIDC smoothing algorithm.[6] Using this algorithm, if the month in question is notated month 0, a weighted average is formed of months −6 to 6, where months −5 to 5 are given weightings of 1, and months −6 and 6 are given weightings of 0.5. 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,[7] with related solar cycles characteristics available in this STCE news item.[8]

The start of solar cycle 25 was declared by SIDC on September 15, 2020 as being in December 2019.[9] This makes cycle 24 the only "11-year solar cycle" to have lasted precisely 11 years.

Details of cycles 1 to 25

[edit]
Solar cycle Start (Min)
(Y-M)		 Min SSN
(start of cycle)		 Max (Y-M) Max SSN Ave spots
per day		 Time of Rise
(Y-M)		 Length (Y-M)
Solar cycle 1 1755 – Feb 14.0 1761 – Jun 144 (70) 6-4 11-4
Solar cycle 2 1766 – Jun 18.6 1769 – Sep 193 (99) 3-3 9-0
Solar cycle 3 1775 – Jun 12.0 1778 – May 264 (111) 2-11 9-3
Solar cycle 4 1784 – Sep 15.9 1788 – Feb 235 (103) 3-5 13-7
Solar cycle 5 1798 – Apr 5.3 1805 – Feb 82 (38) 6-10 12-3
Solar cycle 6 1810 – Jul 0.0 1816 – May 81 (31) 5-10 12-10
Solar cycle 7 1823 – May 0.1 1829 – Nov 119 (63) 6-6 10-6
Solar cycle 8 1833 – Nov 12.2 1837 – Mar 245 (112) 3-4 9-8
Solar cycle 9 1843 – Jul 17.6 1848 – Feb 220 (99) 4-7 12-5
Solar cycle 10 1855 – Dec 6.0 1860 – Feb 186 92 4-2 11-3
Solar cycle 11 1867 – Mar 9.9 1870 – Aug 234 89 3-5 11-9
Solar cycle 12 1878 – Dec 3.7 1883 – Dec 124 57 5-0 11-3
Solar cycle 13 1890 – Mar 8.3 1894 – Jan 147 65 3-10 11-10
Solar cycle 14 1902 – Jan 4.5 1906 – Feb 107 54 4-1 11-6
Solar cycle 15 1913 – Jul 2.5 1917 – Aug 176 73 4-1 10-1
Solar cycle 16 1923 – Aug 9.3 1928 – Apr 130 68 4-8 10-1
Solar cycle 17 1933 – Sep 5.8 1937 – Apr 199 96 3-7 10-5
Solar cycle 18 1944 – Feb 12.9 1947 – May 219 109 3-3 10-2
Solar cycle 19 1954 – Apr 5.1 1958 – Mar 285 129 3-11 10-6
Solar cycle 20 1964 – Oct 14.3 1968 – Nov 157 86 4-1 11-5
Solar cycle 21 1976 – Mar 17.8 1979 – Dec 233 111 3-9 10-6
Solar cycle 22 1986 – Sep 13.5 1989 – Nov 213 106 3-2 9-11
Solar cycle 23 1996 – Aug 11.2 2001 – Nov 180 82 5-3 12-4
Solar cycle 24 2008 – Dec 2.2 2014 – Apr 116 49 5-4 11-0
Solar cycle 25 2019 – Dec 1.8 2024 – Oct 161 Progr:
SC25 (87)
SC24 (66)		 4–10
Median 9.3 180 4–1 11–3
  • Notes on Solar cycle 25
    • The maximum SSN of 160.9 for October 2024 is 73% above the maximum SSN predicted by Zharkova for SC25.
    • SILSO has announced October 2024 as the peak of the cycle. It says: "For the coming years, another maximum remains a possibility, but it is unlikely it will be higher than the one in October last year because the Sun has completed its polar field reversal in 2023, and because the ongoing solar cycle is already 5.5 years in progress."
    • As at April 30, 2026, SC 25 is averaging 30% more spots per day that SC24 at the same stage in the cycle.

Unofficial cycles starting with a maximum

[edit]

The following table is instead divided into (unofficial) cycles starting and ending with a maximum, for the purpose of indicating the number of spotless days associated with each minimum. It begins with cycle 10-11 due to the significant amount of missing daily data before this time, which allows estimated averages to be calculated, but does not permit totals to be counted.

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 cycle 18–19 1947 – May 446
Solar cycle 19–20 1958 – Mar 227
Solar cycle 20–21 1968 – Nov 272
Solar cycle 21–22 1979 – Dec 273
Solar cycle 22–23 1989 – Oct 309
Solar cycle 23–24 2001 – Nov 817
Solar cycle 24–25 2014 – Apr 849
Solar cycle 25–26 2024 – Oct 0

References

[edit]
  1. ↑ "Sunspot numbers". WDC-SILSO. Royal Observatory of Belgium. Retrieved 19 May 2017.
  2. ↑ Hathaway, D. (2015). "The solar cycle". Living Reviews in Solar Physics. 12 (1): 4. arXiv:1502.07020. Bibcode:2015LRSP...12....4H. doi:10.1007/lrsp-2015-4. PMC 4841188. PMID 27194958.
  3. ↑ Usoskin; Mursula; Kovaltsov (2001). "Heliospheric modulation of cosmic rays and solar activity during the Maunder minimum". J. Geophys. Res. 106(A8) (A8): 16039. Bibcode:2001JGR...10616039U. doi:10.1029/2000JA000105.
  4. ↑ Usoskin; et al. (2009). "A solar cycle lost in 1793-1800: Early sunspot observations resolve the old mystery". Astrophys. J. Lett. 700 (2): L154. arXiv:0907.0063. Bibcode:2009ApJ...700L.154U. doi:10.1088/0004-637X/700/2/L154. S2CID 14882350.
  5. ↑ Usoskin; et al. (2021). "Solar cyclic activity over the last millennium reconstructed from annual 14C data". Astron. Astrophys. 649: A141. arXiv:2103.15112. doi:10.1051/0004-6361/202140711.
  6. ↑ "SIDC smoothing formula". WDC-SILSO. Royal Observatory of Belgium. Retrieved 1 Jun 2025.
  7. ↑ Meeus, J. (1958). "Une formule d'adoucissement pour l'activité solaire". Ciel et Terre. 74: 445. Bibcode:1958C&T....74..445M.
  8. ↑ "The solar cycle's new clothes". STCE. Royal Observatory of Belgium. Retrieved 8 July 2015.
  9. ↑ "December 2019 confirmed as starting point of the new solar activity cycle". SIDC.
  10. ↑ "Spotless Days Page". SILSO. Royal Observatory of Belgium. Retrieved 3 April 2017.
[edit]
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