page_title: Maunder Minimum
section_title: Other observations
hierarchical_section_title: Maunder Minimum / Other observations
context_page_description: The Maunder Minimum, also known as the "prolonged sunspot minimum", is the name used for the period around 1645 to 1715 during which sunspots became exceedingly rare, as was then noted by solar observers.
  The term was introduced after John A. Eddy published a landmark 1976 paper in Science. Astronomers before Eddy had also named the period after the solar astronomers Annie Russell Maunder and her husband, Edward Walter Maunder, who studied how sunspot latitudes changed with time. The period which the Maunders examined included the second half of the 17th century.
  Two papers were published in Edward Maunder's name in 1890 and 1894, and he cited earlier papers written by Gustav Spörer. Because Annie Maunder had not received a university degree, restrictions at the time caused her contribution not to be publicly recognized. Spörer noted that, during a 28-year period within the Maunder Minimum, observations revealed fewer than 50 sunspots. This contrasts with the typical 40,000–50,000 sunspots seen in modern times.
  The Maunder Minimum occurred with a much longer period of lower-than-average European temperatures which is likely to have been primarily caused by volcanic activity.
context_section_description: Past solar activity may be recorded by various proxies, including carbon-14 and beryllium-10. 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 archaeological artifacts. The interpretation of the beryllium-10 and carbon-14 cosmogenic isotope abundance records stored in terrestrial reservoirs such as ice sheets and tree rings 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.
  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.  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 Flamsteed drawing suggests that the Sun's surface rotation slowed in the deep Maunder minimum (1684).
  During the Maunder Minimum aurorae had been observed seemingly normally, with a regular decadal-scale cycle. 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.  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. 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)  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.
  The fundamental papers on the Maunder minimum have been published in Case studies on the Spörer, Maunder and Dalton Minima.
caption: Graph showing proxies of solar activity, including changes in sunspot number and cosmogenic isotope production.
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