List of solar cycles

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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 start in 1755 when Rudolf Wolf began extensive reporting of sunspot activity. 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 (Minimum) Smoothed minimum ISN (start of cycle) Maximum Smoothed maximum ISN Average spots per day Time of Rise
(Y-M)
Duration
(Y-M)
Spotless days[10][11]
Solar cycle 1 1755-02 14.0 1761-06 144 (70) 6-4 11-4
Solar cycle 2 1766-06 18.6 1769-09 193 (99) 3-3 9-0
Solar cycle 3 1775-06 12.0 1778-05 264 (111) 2-11 9-3
Solar cycle 4 1784-09 15.9 1788-02 235 (103) 3-5 13-7
Solar cycle 5 1798-04 5.3 1805-02 82 (38) 6-10 12-3
Solar cycle 6 1810-07 0.0 1816-05 81 (31) 5-10 12-10
Solar cycle 7 1823-05 0.1 1829-11 119 (63) 6-6 10-6
Solar cycle 8 1833-11 12.2 1837-03 245 (112) 3-4 9-8
Solar cycle 9 1843-07 17.6 1848-02 220 (99) 4-7 12-5
Solar cycle 10 1855-12 6.0 1860-02 186 92 4-2 11-3 561
Solar cycle 11 1867-03 9.9 1870-08 234 89 3-5 11-9 942
Solar cycle 12 1878-12 3.7 1883-12 124 57 5-0 11-3 872
Solar cycle 13 1890-03 8.3 1894-01 147 65 3-10 11-10 782
Solar cycle 14 1902-01 4.5 1906-02 107 54 4-1 11-6 1007
Solar cycle 15 1913-07 2.5 1917-08 176 73 4-1 10-1 640
Solar cycle 16 1923-08 9.3 1928-04 130 68 4-8 10-1 514
Solar cycle 17 1933-09 5.8 1937-04 199 96 3-7 10-5 384
Solar cycle 18 1944-02 12.9 1947-05 219 109 3-3 10-2 382
Solar cycle 19 1954-04 5.1 1958-03 285 129 3-11 10-6 337
Solar cycle 20 1964-10 14.3 1968-11 157 86 4-1 11-5 285
Solar cycle 21 1976-03 17.8 1979-12 233 111 3-9 10-6 283
Solar cycle 22 1986-09 13.5 1989-11 213 106 3-2 9-11 257
Solar cycle 23 1996-08 11.2 2001-11 180 82 5-3 12-4 619
Solar cycle 24 2008-12 2.2 2014-04 116 49 5-4 11-0 914
Solar cycle 25 2019-12 1.8 Progressive: 73 (Apr 2022)

(Same point last cycle: 61)

270 (Nov 152022)

(Same point last cycle: 336)

Average 9.0 178.7 4.4 11.04

Unofficial cycles starting with a maximum[edit]

The following table is instead divided into (unofficial) cycles starting and ending with a maximum, to give a better feel for the number of spotless days associated with each minimum:

Solar Cycles “Start” (Maximum) Spotless days
Solar cycle 10-11 1860-02 406
Solar cycle 11-12 1870-08 1028
Solar cycle 12-13 1883-12 736
Solar cycle 13-14 1894-01 934
Solar cycle 14-15 1906-02 1023
Solar cycle 15-16 1917-08 534
Solar cycle 16-17 1928-04 568
Solar cycle 17-18 1937-04 269
Solar cycle 18-19 1947-05 446
Solar cycle 19-20 1958-03 227
Solar cycle 20-21 1968-11 272
Solar cycle 21-22 1979-12 273
Solar cycle 22-23 1989-10 309
Solar cycle 23-24 2001-11 817
Solar cycle 24-25 2014-04 848 (Nov 15 2022)

[Same point last cycle: 817]

Comparison of cycles 24 and 25 by 13-month Running Averages[edit]

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 (Nov 15 2022) and six months after the end of the month in question.
The table shows averages for each hemisphere and the average for the entire Sun.

Solar Cycle 24 Solar Cycle 25
North South Total Total South North
Dec 2008 1.4 0.8 2.2 1.8 0.9 0.9 Dec 2019
Jan 2009 1.6 0.9 2.5 2.2 1.3 0.9 Jan 2020
Feb 2009 1.6 1.1 2.7 2.7 1.5 1.2 Feb 2020
Mar 2009 1.7 1.2 2.9 3.0 1.5 1.5 Mar 2020
Apr 2009 2.1 1.2 3.3 3.6 2.1 1.5 Apr 2020
May 2009 2.3 1.2 3.5 5.6 3.9 1.6 May 2020
Jun 2009 2.7 1.4 4.1 7.9 6.1 1.8 Jun 2020
Jul 2009 3.6 1.9 5.5 9.0 7.3 1.7 Jul 2020
Aug 2009 4.9 2.5 7.4 9.5 7.6 1.9 Aug 2020
Sep 2009 6.5 3.0 9.5 10 7.9 2.5 Sep 2020
Oct 2009 7.3 3.3 11 12 8.9 3.0 Oct 2020
Nov 2009 8.1 3.6 12 14 9.8 3.8 Nov 2020
Dec 2009 8.4 4.3 13 15 10 5.1 Dec 2020
Jan 2010 9.0 5.0 14 17 11 6.3 Jan 2021
Feb 2010 10 5.6 16 19 12 7.2 Feb 2021
Mar 2010 12 6.4 19 22 14 8.0 Mar 2021
Apr 2010 13 7.4 21 25 16 9.2 Apr 2021
May 2010 15 8.4 23 26 15 10 May 2021
Jun 2010 16 8.8 25 28 16 12 Jun 2021
Jul 2010 17 8.7 25 31 18 13 Jul 2021
Aug 2010 17 9.3 26 35 20 16 Aug 2021
Sep 2010 19 10 29 40 22 18 Sep 2021
Oct 2010 23 12 34 45 24 21 Oct 2021
Nov 2010 26 13 39 51 27 24 Nov 2021
Dec 2010 28 14 42 56 30 26 Dec 2021
Jan 2011 31 15 46 60 32 28 Jan 2022
Feb 2011 34 15 49 65 35 30 Feb 2022
Mar 2011 38 16 54 69 37 31 Mar 2022
Apr 2011 44 17 61 73 39 34 Apr 2022
May 2011 50 20 69 (76) May 2022
Jun 2011 54 23 77 (73) Jun 2022
Jul 2011 58 26 84 (68) Jul 2022
Aug 2011 60 26 86 (63) Aug 2022
Sep 2011 60 27 87 (58) Sep 2022
Oct 2011 59 28 87 (51) Oct 2022
Nov 2011 59 30 89 (43) Nov 2022
Dec 2011 60 33 92 Dec 2022
Jan 2012 59 36 95 Jan 2023
Feb 2012 58 41 98 Feb 2023
Mar 2012 55 43 98 Mar 2023
Apr 2012 51 44 95 Apr 2023
May 2012 47 44 91 May 2023
Jun 2012 45 42 87 Jun 2023
Jul 2012 44 40 84 Jul 2023
Aug 2012 44 41 85 Aug 2023
Sep 2012 44 41 85 Sep 2023
Oct 2012 45 41 86 Oct 2023
Nov 2012 46 42 88 Nov 2023
Dec 2012 45 43 88 Dec 2023
Jan 2013 45 42 87 Jan 2024
Feb 2013 44 42 86 Feb 2024
Mar 2013 43 42 84 Mar 2024
Apr 2013 42 42 84 Apr 2024
May 2013 41 46 87 May 2024
Jun 2013 39 52 91 Jun 2024
Jul 2013 37 58 95 Jul 2024
Aug 2013 35 64 99 Aug 2024
Sep 2013 35 70 105 Sep 2024
Oct 2013 34 73 107 Oct 2024
Nov 2013 32 74 107 Nov 2024
Dec 2013 32 76 108 Dec 2024
Jan 2014 33 76 109 Jan 2025
Feb 2014 35 76 111 Feb 2025
Mar 2014 36 78 114 Mar 2025
Apr 2014 36 80 116 Apr 2025

Comparison of Cycles 24 and 25 by Daily Spots[edit]

The following table gives the number of days so far in cycle 25 (to Nov 1 2022), and up to the same point in cycle 24 (to Nov 1 2011), which have passed various thresholds for the numbers of sunspots.

Count
Groupings
Solar Cycle
24 25
≥75 sunspots 141 212
≥100 83 96
≥125 47 47
≥150 20 13
≥175 6 0

As at Nov 15 2022, solar cycle 25 is averaging 14% more spots per day than solar cycle 24 at the same point in the cycle (Nov 152011).

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. "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 19 May 2017.
  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. ^ "What's Wrong with the Sun?". NASA Science. NASA. Retrieved 29 July 2014.
  11. ^ "Spotless Days Page". SILSO. Royal Observatory of Belgium. Retrieved 3 April 2017.

External links[edit]