Editing Solar cycle (section)

=== Sunspots ===
{{Main|Sunspot}}
[[File:ChroniclesofJohnofWorcester.jpg|thumb|upright=1.15|A [[Sunspot drawing|drawing of a sunspot]] in the Chronicles of [[John of Worcester]], ca. 1100<ref>{{Cite web |url=https://sunearthday.nasa.gov/2006/locations/firstdrawing.php |title=NASA – Sun-Earth Day – Technology Through Time – Greece |website=sunearthday.nasa.gov}}</ref>]]
The Sun's apparent surface, the photosphere, radiates more actively when there are more sunspots. Satellite monitoring of [[solar luminosity]] revealed a direct relationship between the solar cycle and luminosity with a peak-to-peak amplitude of about 0.1%.<ref name="Willson91">{{cite journal |last = Willson|first = Richard C.|author2 = H.S. Hudson|year = 1991|title = The Sun's luminosity over a complete solar cycle|journal = Nature|volume = 351|issue = 6321|pages = 42–4|doi = 10.1038/351042a0|bibcode = 1991Natur.351...42W|s2cid = 4273483}}<!-- {{harvnb|Willson|1991}} --></ref> Luminosity decreases by as much as 0.3% on a 10-day timescale when large groups of sunspots rotate across the Earth's view and increase by as much as 0.05% for up to 6 months due to [[Solar facula|faculae]] associated with large sunspot groups.<ref name="Willson81">{{Cite journal |vauthors=Willson RC, Gulkis S, Janssen M, Hudson HS, Chapman GA |title = Observations of Solar Irradiance Variability|journal = Science|volume = 211|issue = 4483|pages = 700–2|date = February 1981|pmid = 17776650|doi = 10.1126/science.211.4483.700|bibcode = 1981Sci...211..700W}}</ref>

The best information today comes from [[Solar and Heliospheric Observatory|SOHO]] (a cooperative project of the [[European Space Agency]] and [[NASA]]), such as the MDI [[Solar magnetogram|magnetogram]], where the solar "surface" [[magnetic field]] can be seen.

As each cycle begins, sunspots appear at mid-latitudes, and then move closer and closer to the equator until a solar minimum is reached. This pattern is best visualized in the form of the so-called butterfly diagram. Images of the Sun are divided into latitudinal strips, and the monthly-averaged fractional surface of sunspots is calculated. This is plotted vertically as a color-coded bar, and the process is repeated month after month to produce this time-series diagram.
[[File:Sun - btly - 2023.png|center|thumb|upright=2.5|This version of the sunspot butterfly diagram was constructed by the solar group at NASA Marshall Space Flight Center. The newest version can be found at [http://solarcyclescience.com/solarcycle.html solarcyclescience.com]]]
While magnetic field changes are concentrated at sunspots, the entire Sun undergoes analogous changes, albeit of smaller magnitude.
[[File:LAMF - 2023.png|center|thumb|upright=2.5|Time vs. solar latitude diagram of the radial component of the solar magnetic field, averaged over successive solar rotation. The "butterfly" signature of sunspots is clearly visible at low latitudes. Diagram constructed by the solar group at NASA Marshall Space Flight Center. The newest version can be found at [http://solarcyclescience.com/solarcycle.html solarcyclescience.com]]]