An Upper Limit on Sunspot Activity During the Maunder Minimum |
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Authors: | G A Kovaltsov I G Usoskin K Mursula |
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Institution: | 1. Ioffe Physical-Technical Institute, 194021, St. Petersburg, Russia 2. Sodankyl? Geophysical Observatory (Oulu unit), University of Oulu, P.O.Box 3000, FIN-90014, Finland 3. Department of Physical Sciences, University of Oulu, P.O.Box 3000, FIN-90014, Finland
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Abstract: | We have estimated the upper and lower limits of sunspot activity, in terms of active day fraction during the Maunder minimum
(1645–1710), using raw information on individual daily observations (Hoyt and Schatten, 1998). Establishing the relation between
the sunspot activity and active day fraction after 1850, we evaluate the upper limit of annual group sunspot number during
the deep Maunder minimum (1645–1700) which does not exceed 4. The earlier finding of a dominant 22-year periodicity during
the Maunder minimum is verified and shown to be robust. Also we confirm that the start of the Maunder minimum was very abrupt. |
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