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An attempt to determine the differential rotation in the 18th century


Arlt Rainer


Astrophysikalisches Institut Potsdam


Solar diameter, irradiance and activity
Auteur(s) supplémentaire(s)Hans-Erich Fröhlich


Based on about 1000 sunspot drawings by Johann Staudacher from 1749-1799, a set of 6300 sunspot positions were determined to construct a butterfly diagram for the 18th century. We now report on recent efforts to determine the differential rotation of the Sun in that period. This is of particular interest, firstly because the modulation of the differential rotation may lead to grand minima, and secondly, because the first two cycles observed by Staudacher show a non-butterfly spot distribution and may have been peculiar.
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