Editing Solar cycle (section)

=== Gleissberg cycle ===

The '''Gleissberg cycle''' describes an amplitude modulation of solar cycles with a period of about 70–100 years, or seven or eight solar cycles. It was named after Wolfgang Gleißberg.<ref name="hathaway_review" /><ref>{{cite journal |first1 = C. P.|last1 = Sonett|first2 = S. A.|last2 = Finney|first3 = A.|last3 = Berger|title = The Spectrum of Radiocarbon|journal = [[Philosophical Transactions of the Royal Society A]]|volume = 330|issue = 1615|pages = 413–26|date = 24 April 1990|doi = 10.1098/rsta.1990.0022|bibcode = 1990RSPTA.330..413S|s2cid = 123641430}}</ref><ref name="Braun05">{{cite journal |title = Possible solar origin of the 1,470-year glacial climate cycle demonstrated in a coupled model|journal = Nature|volume = 438|pages = 208–11|date = 10 November 2005|doi = 10.1038/nature04121|pmid = 16281042|last1 = Braun|first1 = H|last2 = Christl|first2 = M|last3 = Rahmstorf|first3 = S|last4 = Ganopolski|first4 = A|last5 = Mangini|first5 = A|last6 = Kubatzki|first6 = C|last7 = Roth|first7 = K|last8 = Kromer|first8 = B|issue = 7065|bibcode = 2005Natur.438..208B|s2cid = 4346459|url = http://epic.awi.de/13582/1/Bra2005e.pdf}}</ref><ref name="Hathaway2005">{{Cite journal |first1 = David H.|last1 = Hathaway|first2 = Robert M.|last2 = Wilson|title = What the Sunspot Record Tells Us About Space Climate|journal = [[Solar Physics (journal)|Solar Physics]]|volume = 224|issue = 1–2|year = 2004|pages = 5–19|doi = 10.1007/s11207-005-3996-8|url = http://science.msfc.nasa.gov/ssl/pad/solar/papers/hathadh/HathawayWilson2004.pdf|access-date = 19 April 2007|archive-url = https://web.archive.org/web/20060104223339/http://science.msfc.nasa.gov/ssl/pad/solar/papers/hathadh/HathawayWilson2004.pdf|archive-date = 4 January 2006|bibcode = 2004SoPh..224....5H|s2cid = 55971262}}</ref>

As pioneered by [[Ilya G. Usoskin]] and [[Sami Solanki]], associated centennial variations in magnetic fields in the [[Solar corona|corona]] and [[heliosphere]] have been detected using [[carbon-14]] and [[beryllium-10]] cosmogenic isotopes stored in terrestrial reservoirs such as [[ice sheet]]s and [[tree ring]]s<ref>{{cite journal |author = Usoskin I.G.| author-link=Ilya G. Usoskin |title = A History of Solar Activity over Millennia|journal = Living Reviews in Solar Physics|volume = 14|issue = 3|page = 3|date = 2017|doi = 10.1007/s41116-017-0006-9|bibcode = 2017LRSP...14....3U |arxiv = 0810.3972|s2cid = 195340740}} [https://link.springer.com/content/pdf/10.1007%2Fs41116-017-0006-9.pdf PDF Copy]</ref> and by using historic observations of [[geomagnetic storm]] activity, which bridge the time gap between the end of the usable cosmogenic isotope data and the start of modern satellite data.<ref>{{cite journal |author = Lockwood M.|title = Reconstruction and Prediction of Variations in the Open Solar Magnetic Flux and Interplanetary Conditions|journal = Living Reviews in Solar Physics|volume = 10|issue = 4|page = 4|date = 2013|doi = 10.12942/lrsp-2013-4|url = http://solarphysics.livingreviews.org/Articles/lrsp-2013-4/|bibcode = 2013LRSP...10....4L|doi-access = free}} [http://solarphysics.livingreviews.org/Articles/lrsp-2013-4/download/lrsp-2013-4Color.pdf PDF Copy]</ref>

These variations have been successfully reproduced using models that employ magnetic flux continuity equations and observed sunspot numbers to quantify the emergence of magnetic flux from the top of the solar atmosphere and into the [[heliosphere]],<ref>{{cite journal |author = Owens M.J.|author2 = Forsyth R.J.|name-list-style = amp|title = The Heliospheric Magnetic Field|journal = Living Reviews in Solar Physics|volume = 10|issue = 5|page = 5|date = 2013|doi = 10.12942/lrsp-2013-5| doi-access=free |url = http://solarphysics.livingreviews.org/Articles/lrsp-2013-5/|bibcode = 2013LRSP...10....5O|arxiv = 1002.2934|s2cid = 122870891}}</ref> showing that sunspot observations, geomagnetic activity and cosmogenic isotopes offer a convergent understanding of solar activity variations.