The following is a
list of solar cycleSolar variations refer here to changes in the amount of total solar radiation and its spectral distribution. There are periodic components to these variations, the principal one being the 11-year solar cycle , as well as aperiodic fluctuations. Solar activity has been measured by satellites during...
s (sometimes called
sunspot cyclesA sunspot is an area on the Sun's surface that is marked by intense magnetic activity, which inhibits convection, forming areas of reduced surface temperature. They can be visible from Earth without the aid of a telescope...
), tracked since 1755.
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The following is a
list of solar cycleSolar variations refer here to changes in the amount of total solar radiation and its spectral distribution. There are periodic components to these variations, the principal one being the 11-year solar cycle , as well as aperiodic fluctuations. Solar activity has been measured by satellites during...
s (sometimes called
sunspot cyclesA sunspot is an area on the Sun's surface that is marked by intense magnetic activity, which inhibits convection, forming areas of reduced surface temperature. They can be visible from Earth without the aid of a telescope...
), tracked since 1755.
Solar Cycles
| Cycle |
Started |
Finished |
Duration (years) |
Maximum (monthly SSN (Smoothed Sunspot Number)) |
Minimum (monthly SSN; end of cycle) |
Spotless Days (end of cycle) |
| 1 |
March 1755 |
June 1766 |
11.3 |
|
11.2 |
|
| 2 |
June 1766 |
June 1775 |
9.0 |
|
7.2 |
|
| 3 |
June 1775 |
September 1784 |
9.3 |
|
9.5 |
|
| 4 |
September 1784 |
May 1798 |
13.7 |
|
3.2 |
|
| 5 |
May 1798 |
December 1810 |
12.6 |
|
0.0 |
|
| 6 |
December 1810 |
May 1823 |
12.4 |
|
0.1 |
|
| 7 |
May 1823 |
November 1833 |
10.5 |
|
7.3 |
|
| 8 |
November 1833 |
July 1843 |
9.8 |
|
10.6 |
|
| 9 |
July 1843 |
December 1855 |
12.4 |
|
3.2 |
~654 |
| 10 |
December 1855 |
March 1867 |
11.3 |
|
5.2 |
~406 |
| 11 |
March 1867 |
December 1878 |
11.8 |
|
2.2 |
~1028 |
| 12 |
December 1878 |
March 1890 |
11.3 |
|
5.0 |
~736 |
| 13 |
March 1890 |
February 1902 |
11.9 |
87.9 (Jan 1894) |
2.7 |
~938 |
| 14 |
February 1902 |
August 1913 |
11.5 |
64.2 (Feb 1906) |
1.5 |
~1019 |
| 15 |
August 1913 |
August 1923 |
10.0 |
105.4 (Aug 1917) |
5.6 |
534 |
| 16 |
August 1923 |
September 1933 |
10.1 |
78.1 (Apr 1928) |
3.5 |
568 |
| 17 |
September 1933 |
February 1944 |
10.4 |
119.2 (Apr 1937) |
7.7 |
269 |
| 18 |
February 1944 |
April 1954 |
10.2 |
151.8 (May 1947) |
3.4 |
446 |
| 19 |
April 1954 |
October 1964 |
10.5 |
201.3 (Mar 1958) |
9.6 |
227 |
| 20 |
October 1964 |
June 1976 |
11.7 |
110.6 (Nov 1968) |
12.2 |
272 |
| 21 |
June 1976 |
September 1986 |
10.3 |
164.5 (Dec 1979) |
12.3 |
273 |
| 22 |
September 1986 |
May 1996 |
9.7 |
158.5 (Jul 1989) |
8.0 |
309 |
| 23 |
May 1996 |
December 2008 (candidate month) |
12.6 |
120.8 (Mar 2000) |
1.7 (lowest so far) |
723 (through October 1, 2009) |
| 24 |
December 2008 (candidate month) |
|
|
|
|
| Mean |
|
|
11.0 |
|
|
485 |
|
Spots from multiple cycles can co-exist for some time and since it was discovered the sun reverses magnetic polarity one solar half cycle to the next, spots from different cycles can be told apart. However it takes some months before a definite decision to be made on the true date of solar minimum, which is announced by the relevant expert authorities.
One of the main authorities is SIDAC (Solar Influences Data Analysis Center) which is located in
BelgiumThe Kingdom of Belgium is a country in northwest Europe. It is a founding member of the European Union and hosts its headquarters, as well as those of other major international organizations, including NATO...
, and works with agencies such as
NASAThe National Aeronautics and Space Administration is an agency of the United States government, responsible for the nation's public space program. NASA was established by the National Aeronautics and Space Act on July 29, 1958, replacing its predecessor, the National Advisory Committee for...
and ESA.
The most important information today comes from SOHO (a project of international cooperation between ESA and NASA), such as the MDI Magnetogram, where the solar "surface"
magnetic fieldMagnetic fields surround magnetic materials and electric currents and are detected by the force they exert on other magnetic materials and moving electric charges...
can be seen.
It has been noticed that sunspots from a dying solar cycle tend to appear near the solar equator whereas spots from a new cycle tend to appear near to the solar poles.
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