Editing Maunder Minimum (section)

==Other observations==
[[Image:Carbon14 with activity labels.svg|thumb|upright=1.4|Solar activity events recorded in radiocarbon.]]
[[Image:Solar Activity Proxies.png|thumb|upright=1.4|Graph showing proxies of solar activity, including changes in sunspot number and cosmogenic isotope production.]]

Past solar activity may be recorded by various [[proxy (climate)|proxies]], including [[carbon-14]] and [[beryllium-10]].<ref>{{cite journal |author=Usoskin I.G. |title=A History of Solar Activity over Millennia |journal=Living Reviews in Solar Physics |volume=14 |issue=3 |pages=3 |date= 2017 |doi= 10.1007/s41116-017-0006-9 |bibcode = 2017LRSP...14....3U |arxiv=0810.3972 |s2cid=195340740 }}</ref> These indicate lower solar activity during the Maunder Minimum.  The scale of changes resulting in the production of carbon-14 in one cycle is small (about one percent of medium abundance) and can be taken into account when [[radiocarbon dating]] is used to determine the age of [[archaeology|archaeological artifacts]]. The interpretation of the [[beryllium-10]] and [[carbon-14]] cosmogenic isotope abundance records stored in terrestrial reservoirs such as [[ice sheet]]s and [[tree ring]]s has been greatly aided by reconstructions of solar and heliospheric magnetic fields based on historic data on [[geomagnetic storm]] activity, which bridge the time gap between the end of the usable cosmogenic isotope data and the start of modern spacecraft data.<ref>{{cite journal |author= Lockwood M. |display-authors= etal |title= A doubling of the sun's coronal magnetic field during the last 100 years |journal= Nature |volume= 399 |issue= 6735 |date= June 1999 |doi= 10.1038/20867 |pages= 437–439 |bibcode= 1999Natur.399..437L |s2cid= 4334972 }} [http://www.eiscat.rl.ac.uk/Members/mike/publications/pdfs/1999/170_Lockwoodetal_nature.pdf PDF Copy] {{webarchive|url=https://web.archive.org/web/20110430124928/http://www.eiscat.rl.ac.uk/Members/mike/publications/pdfs/1999/170_Lockwoodetal_nature.pdf |date=2011-04-30 }}</ref><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 |pages= 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>

Other historical sunspot minima have been detected either directly or by the analysis of the cosmogenic isotopes; these include the [[Spörer Minimum]] (1450–1540), and less markedly the [[Dalton Minimum]] (1790–1820).  In a 2012 study, sunspot minima have been detected by analysis of carbon-14 in lake sediments.<ref name="SedimentStudy">{{cite journal | title=Regional atmospheric circulation shifts induced by a grand solar minimum | journal=[[Nature Geoscience]] |date=April 2, 2012 |author1=Celia Martin-Puertas |author2=Katja Matthes |author3=Achim Brauer |author4=Raimund Muscheler |author5=Felicitas Hansen |author6=Christof Petrick |author7=Ala Aldahan |author8=Göran Possnert |author9=Bas van Geel |volume=5 |pages=397–401 |bibcode = 2012NatGe...5..397M |doi = 10.1038/ngeo1460 |issue=6}}</ref>  In total, there seem to have been 18 periods of sunspot minima in the last 8,000 years, and studies indicate that the Sun currently spends up to a quarter of its time in these minima.

A paper based on an analysis of a drawing by [[John Flamsteed]] suggests that the Sun's surface rotation slowed in the deep Maunder Minimum (1684).<ref>{{cite journal |vauthors=Vaquero JM, Sánchez-Bajo F, Gallego MC | title = A Measure of the Solar Rotation During the Maunder Minimum | journal = Solar Physics | date = 2002 | volume = 207 | issue = 2 | pages = 219–222 | doi =10.1023/A:1016262813525|bibcode = 2002SoPh..207..219V | s2cid = 119037415 }}</ref>

During the Maunder Minimum [[aurora]]e had been observed seemingly normally, with a regular decadal-scale cycle.<ref>{{cite journal |last=Schröder |first=Wilfried | date = 1992 | title = On the existence of the 11-year cycle in solar and auroral activity before and during the Maunder Minimum | journal = Journal of Geomagnetism and Geoelectricity | volume= 44 | issue= 2 | pages= 119–28 | issn= 0022-1392 |doi=10.5636/jgg.44.119 |bibcode = 1992JGG....44..119S | doi-access= free }}</ref><ref>{{cite journal | last1 = Legrand | first1 = JP | last2 = Le Goff | first2 = M | last3= Mazaudier | first3 = C | last4 = Schröder | first4 = W |date = 1992 |title = Solar and auroral activities during the seventeenth century |journal = Acta Geodaetica et Geophysica Hungarica | volume =27 |issue=2–4 |pages=251–282 }}</ref> This is somewhat surprising because the later, and less deep, Dalton sunspot minimum is clearly seen in auroral occurrence frequency, at least at lower geomagnetic latitudes.<ref>{{cite journal |author= Nevanlinna, H. | date = 1995 | title =Auroral observations in Finland – Visual sightings during the 18th and 19th centuries | journal = Journal of Geomagnetism and Geoelectricity | volume= 47 | issue= 10 | pages= 953–960 | issn= 0022-1392 | doi=10.5636/jgg.47.953|bibcode = 1995JGG....47..953N | s2cid = 129392285 |url= http://pdfs.semanticscholar.org/ec72/ea0bcf8d54c21d2afaa1f1fedec83a32a778.pdf |archive-url= https://web.archive.org/web/20200110214031/http://pdfs.semanticscholar.org/ec72/ea0bcf8d54c21d2afaa1f1fedec83a32a778.pdf |url-status= dead |archive-date= 2020-01-10 }} [https://www.jstage.jst.go.jp/article/jgg1949/47/10/47_10_953/_pdf PDF Copy]</ref>  Because geomagnetic latitude is an important factor in auroral occurrence, (lower-latitude aurorae requiring higher levels of solar-terrestrial activity) it becomes important to allow for population migration and other factors that may have influenced the number of reliable auroral observers at a given magnetic latitude for the earlier dates.<ref>{{cite journal |author = Vázquez, M. |display-authors = etal | date = 2014 | title = Long-term Spatial and Temporal Variations of Aurora Borealis Events in the Period 1700 – 1905 | journal = Solar Physics | volume= 289 | issue= 5 | pages= 1843–1861 | issn= 0038-0938 | doi= 10.1007/s11207-013-0413-6|arxiv = 1309.1502 |bibcode = 2014SoPh..289.1843V |s2cid = 119115964 }}</ref> Decadal-scale cycles during the Maunder Minimum can also be seen in the abundances of the [[beryllium-10]] cosmogenic isotope (which unlike [[carbon-14]] can be studied with annual resolution)<ref>{{cite journal |author = Beer, J. |display-authors = etal | date = 1988 | title = An Active Sun Throughout the Maunder Minimum | journal = Solar Physics | volume= 181 | issue= 1 | pages= 237–249 | doi= 10.1023/A:1005026001784|bibcode = 1998SoPh..181..237B |s2cid = 122019951 |url = https://www.dora.lib4ri.ch/eawag/islandora/object/eawag%3A3949 | url-access = subscription }} [http://www.predsci.com/ESWE-workshop/session2_9/An%20active%20Sun%20throughout%20the%20Maunder%20minimum.pdf PDF Copy] {{webarchive|url=https://web.archive.org/web/20140821131351/http://www.predsci.com/ESWE-workshop/session2_9/An%20active%20Sun%20throughout%20the%20Maunder%20minimum.pdf |date=2014-08-21 }}</ref> but these appear to be in antiphase with any remnant sunspot activity. An explanation in terms of solar cycles in loss of solar magnetic flux was proposed in 2012.<ref>{{cite journal | author= Owens, M.J.. | display-authors= etal | date= 2012 | title= Heliospheric modulation of galactic cosmic rays during grand solar minima: Past and future variations | journal= Geophys. Res. Lett. | volume= 39 | issue= 19 | pages= L19102 | doi= 10.1029/2012GL053151 | bibcode= 2012GeoRL..3919102O | url= https://zenodo.org/record/897863 | doi-access= free }} [http://www.eiscat.rl.ac.uk/Members/mike/publications/pdfs/2012/289_Owensetal2012GL053151.pdf PDF Copy] {{webarchive|url=https://web.archive.org/web/20140822123743/http://www.eiscat.rl.ac.uk/Members/mike/publications/pdfs/2012/289_Owensetal2012GL053151.pdf |date=2014-08-22 }}</ref>

The fundamental papers on the Maunder Minimum have been published in ''Case studies on the Spörer, Maunder and Dalton Minima''.<ref>{{cite book |title= Case studies on the Spörer, Maunder, and Dalton minima |last= Schröder |first= Wilfried |date= 2005 |series= Beiträge zur Geschichte der Geophysik und Kosmischen Physik |volume=6 |publisher=AKGGP, Science Edition |location=Potsdam }}</ref>