Maunder Minimum: Difference between revisions
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The '''Maunder Minimum''' is the name given to the period roughly from [[1645]] to [[1715]] A.D., when [[sunspot]]s became exceedingly rare, as noted by solar observers of the time. It is named after the later solar astronomer [[E.W. Maunder]] who discovered the dearth of sunspots during that period by studying records from those years. During one 30-year period within the Maunder Minimum, for example, astronomers observed only about 50 sunspots, as opposed to a more typical 40,000–50,000 spots. |
The '''Maunder Minimum''' is the name given to the period roughly from [[1645]] to [[1715]] A.D., when [[sunspot]]s became exceedingly rare, as noted by solar observers of the time. It is named after the later solar astronomer [[E.W. Maunder]] who discovered the dearth of sunspots during that period by studying records from those years. During one 30-year period within the Maunder Minimum, for example, astronomers observed only about 50 sunspots, as opposed to a more typical 40,000–50,000 spots. |
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The Maunder Minimum occurred between 1645 and 1715 when only about 50 spots appeared as opposed to the typical 40-50,000 spots. The minima counts for 10-year periods from 1610-1681 are as follows: |
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1610 to 1619: 9 spots |
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1620 to 1629: 6 spots |
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Year 1639: 9 spots |
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1640 to 1649: 2 spots |
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1650 to 1659: 3 spots |
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1660 to 1669: 1 spot |
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1670 to 1671: 0 spots |
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1680 to 1681: 1 spot |
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During the Maunder Minimum enough sunspots were sighted so that 11-year cycles could be extrapolated from the count. The maxima occurred in 1674, 1684, 1695, 1705 and 1716. |
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The sunspot activity was then concentrated in the southern hemisphere of the sun, except for the last cycle when the sunspots appeared in the northern hemisphere too. |
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According to Sporer’s Law, at the start of a cycle spots appear at ever lower latitudes, until they average at about lat. 15˚ at solar maximum. The average then continues to drift lower to about 7˚ and after that, while spots of the old cycle fade, new cycle spots start appearing again at high latitudes. |
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The visibility of these spots is also affected by the velocity of the sun’s rotation at various latitudes: |
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Lat. 0 in 24.7 days (sun’s equator) |
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Lat. 35 in 26.7 days |
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Lat. 40 in 28.0 days |
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Lat. 75 in 33.0 days |
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In assessing the above values, it should be considered that the orbits of the planets are all mostly in the same plane called the ecliptic which is defined by the plane of the Earth’s actual orbit. The ecliptic is inclined only 7˚ from the plane of the sun’s equator. |
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The Maunder Minimum coincided with the middle — and coldest part — of the so-called [[Little Ice Age]], during which [[Europe]] and [[North America]], and perhaps much of the rest of the world, were subjected to bitterly cold winters. Recently published research suggests that the [[Sun]]'s rotation slowed in the deep Maunder minimum (1666-1700) [1]. At our current level of understanding of solar physics, a larger and slower Sun necessarily implies a cooler Sun that provides less heat to [[Earth]]. (The mechanism behind the Sun's expansion and contraction is still unclear, although many stars undergo pulsations to some degree or another; see [[variable star]].) |
The Maunder Minimum coincided with the middle — and coldest part — of the so-called [[Little Ice Age]], during which [[Europe]] and [[North America]], and perhaps much of the rest of the world, were subjected to bitterly cold winters. Recently published research suggests that the [[Sun]]'s rotation slowed in the deep Maunder minimum (1666-1700) [1]. At our current level of understanding of solar physics, a larger and slower Sun necessarily implies a cooler Sun that provides less heat to [[Earth]]. (The mechanism behind the Sun's expansion and contraction is still unclear, although many stars undergo pulsations to some degree or another; see [[variable star]].) |
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Revision as of 17:31, 19 March 2005
The Maunder Minimum is the name given to the period roughly from 1645 to 1715 A.D., when sunspots became exceedingly rare, as noted by solar observers of the time. It is named after the later solar astronomer E.W. Maunder who discovered the dearth of sunspots during that period by studying records from those years. During one 30-year period within the Maunder Minimum, for example, astronomers observed only about 50 sunspots, as opposed to a more typical 40,000–50,000 spots.
The Maunder Minimum occurred between 1645 and 1715 when only about 50 spots appeared as opposed to the typical 40-50,000 spots. The minima counts for 10-year periods from 1610-1681 are as follows:
1610 to 1619: 9 spots
1620 to 1629: 6 spots
Year 1639: 9 spots
1640 to 1649: 2 spots
1650 to 1659: 3 spots
1660 to 1669: 1 spot
1670 to 1671: 0 spots
1680 to 1681: 1 spot
During the Maunder Minimum enough sunspots were sighted so that 11-year cycles could be extrapolated from the count. The maxima occurred in 1674, 1684, 1695, 1705 and 1716.
The sunspot activity was then concentrated in the southern hemisphere of the sun, except for the last cycle when the sunspots appeared in the northern hemisphere too.
According to Sporer’s Law, at the start of a cycle spots appear at ever lower latitudes, until they average at about lat. 15˚ at solar maximum. The average then continues to drift lower to about 7˚ and after that, while spots of the old cycle fade, new cycle spots start appearing again at high latitudes.
The visibility of these spots is also affected by the velocity of the sun’s rotation at various latitudes:
Lat. 0 in 24.7 days (sun’s equator)
Lat. 35 in 26.7 days
Lat. 40 in 28.0 days
Lat. 75 in 33.0 days
In assessing the above values, it should be considered that the orbits of the planets are all mostly in the same plane called the ecliptic which is defined by the plane of the Earth’s actual orbit. The ecliptic is inclined only 7˚ from the plane of the sun’s equator.
The Maunder Minimum coincided with the middle — and coldest part — of the so-called Little Ice Age, during which Europe and North America, and perhaps much of the rest of the world, were subjected to bitterly cold winters. Recently published research suggests that the Sun's rotation slowed in the deep Maunder minimum (1666-1700) [1]. At our current level of understanding of solar physics, a larger and slower Sun necessarily implies a cooler Sun that provides less heat to Earth. (The mechanism behind the Sun's expansion and contraction is still unclear, although many stars undergo pulsations to some degree or another; see variable star.)
Whether there is a causal connection between low sunspot activity and cold winters is the subject of ongoing debate. Some scientists believe that solar variation drives climate change more than carbon dioxide does (see global warming).
The lower solar activity during the Maunder Minimum also affected the amount of cosmic radiation reaching the Earth. The resulting change in the production of carbon-14 during that period caused an inaccuracy in radiocarbon dating until this effect was discovered.
Solar activity also affects the production of beryllium-10, and variations in that cosmogenic isotope are studied as a proxy for solar activity.
Other historical sunspot minima have been detected either directly or by the analysis of carbon-14 in ice cores or tree rings; these include the Sporer Minimum (1450–1540), and less markedly the Dalton Minimum (1790–1820). 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.
References
- Vaquero J.M., Sánchez-bajo F., Gallego M.C. (2002), A Measure of the Solar Rotation During the Maunder Minimum, Solar Physics, v.207, p.219 doi:10.1023/A:1016262813525