Editing Solar cycle (section)

=== Faculae and plage ===
{{Main|Solar facula|Solar plage}}
[[File:Plage areas chatzistergos 2020.png|thumb|upright=1.35|Solar plage area evolution over time]]
Faculae are bright magnetic features on the photosphere. They extend into the chromosphere, where they are referred to as plage. The evolution of plage areas is typically tracked from solar observations in the Ca II K line (393.37&nbsp;nm).<ref>{{Cite journal |last1=Chatzistergos |first1=Theodosios |last2=Krivova |first2=Natalie A. |last3=Ermolli |first3=Ilaria |date=2022-11-17 |title=Full-disc Ca ii K observations—A window to past solar magnetism |journal=Frontiers in Astronomy and Space Sciences |volume=9 |page=1038949 |doi=10.3389/fspas.2022.1038949 |arxiv=2210.13285 |bibcode=2022FrASS...938949C |issn=2296-987X|doi-access=free }}</ref> The amount of facula and plage area varies in phase with the solar cycle, and they are more abundant than sunspots by approximately an order of magnitude.<ref name="Chatzistergos2020">{{Cite journal |vauthors=Chatzistergos T, Ermolli I, Krivova NA, Solanki SK, Banerjee D, Barata T, Belik M, et al. |title = Analysis of full-disc Ca II K spectroheliograms – III. Plage area composite series covering 1892–2019|journal = Astronomy and Astrophysics|volume = 639|pages = A88|date = July 2020|doi = 10.1051/0004-6361/202037746| arxiv=2005.01435 |bibcode = 2020A&A...639A..88C| s2cid=218487277 }}</ref> They exhibit a non linear relation to sunspots.<ref>{{Cite journal |last1=Chatzistergos |first1=Theodosios |last2=Ermolli |first2=Ilaria |last3=Krivova |first3=Natalie A. |last4=Barata |first4=Teresa |last5=Carvalho |first5=Sara |last6=Malherbe |first6=Jean-Marie |date=November 2022 |title=Scrutinising the relationship between plage areas and sunspot areas and numbers |url=https://www.aanda.org/10.1051/0004-6361/202244913 |journal=Astronomy & Astrophysics |volume=667 |pages=A167 |doi=10.1051/0004-6361/202244913 |arxiv=2209.07077 |bibcode=2022A&A...667A.167C |s2cid=252280541 |issn=0004-6361}}</ref> Plage regions are also associated with strong magnetic fields in the solar surface.<ref>{{Cite journal |last1=Chatzistergos |first1=Theodosios |last2=Ermolli |first2=Ilaria |last3=Solanki |first3=Sami K. |last4=Krivova |first4=Natalie A. |last5=Giorgi |first5=Fabrizio |last6=Yeo |first6=Kok Leng |date=June 2019 |title=Recovering the unsigned photospheric magnetic field from Ca II K observations |url=https://www.aanda.org/10.1051/0004-6361/201935131 |journal=Astronomy & Astrophysics |volume=626 |pages=A114 |doi=10.1051/0004-6361/201935131 |arxiv=1905.03453 |bibcode=2019A&A...626A.114C |s2cid=148571864 |issn=0004-6361}}</ref><ref>{{Cite journal |last1=Babcock |first1=Horace W. |last2=Babcock |first2=Harold D. |date=March 1955 |title=The Sun's Magnetic Field, 1952–1954. |journal=The Astrophysical Journal |language=en |volume=121 |page=349 |doi=10.1086/145994 |bibcode=1955ApJ...121..349B |issn=0004-637X|doi-access= }}</ref>