Solar cycle 4 was the fourth
solar cycle
The solar cycle, also known as the solar magnetic activity cycle, sunspot cycle, or Schwabe cycle, is a nearly periodic 11-year change in the Sun's activity measured in terms of variations in the number of observed sunspots on the Sun's surfa ...
since 1755, when extensive recording of solar
sunspot activity began.
[Kane, R.P. (2002).]
Some Implications Using the Group Sunspot Number Reconstruction
. ''Solar Physics'' 205(2), 383–401. The solar cycle lasted 13.6 years, beginning in September 1784 and ending in April 1798 (thus overlapping the
Dalton Minimum
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 or 1796 to 1820, corresponding to the period solar cycle 4 to solar cycle ...
). The maximum
smoothed sunspot number
The Wolf number (also known as the relative sunspot number or Zürich number) is a quantity that measures the number of sunspots and groups of sunspots present on the surface of the Sun.
History
Astronomers have been observing the Sun recordi ...
observed during the solar cycle was 235.3 (in February 1788), and the starting minimum was 15.9.
[SIDC Monthly Smoothed Sunspot Number.]
There are some recent speculations that cycle 4, the longest solar cycle since 1755, was actually two cycles, based on the appearance of new sunspots at high solar latitudes in 1793–1796 and a reconstruction of the sunspot butterfly diagram for cycles 3 and 4,
"Centuries-old sketches solve sunspot mystery"
''New Scientist'', 1 August 2009, p. 10. although total sunspot numbers only show a single-peaked distribution.
See also
*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 start in 1755 when Rudolf Wolf began extensive reporting ...
References
4
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