Die Sonnenaktivität im Dalton-Minimum
Zusammenfassung der Projektergebnisse
The Dalton minimum of solar activity occurred near 1800 CE and lasted about 20-30 years. Observations of before and after the minimum may show peculiarities in the properties of sunspot groups, for example in terms of latitudes or tilt-angles against the solar equator. We therefore need drawings of the Sun or measurements of sunspot positions for the aim of the project. Since potential peculiarities will show up only in a statistical sense, as many historical sources as possible need to be found and utilized. Sunspot observations of five observers/observatories from periods near or within the Dalton minimum were analysed in terms of heliographic sunspot positions, which add information to the hitherto published sunspot or group counts. The observations studied in this project confirm that the solar activity in the Dalton minimum was lower than in the middle of the 18th century as well as lower than in the middle of the 19th century. The activity, however, was by far not as low as in the Maunder minimum in the second half of the 17th century. Situations observed in the latter case, when no sunspots had been seen for a year or more, were not found in the Dalton minimum. The peculiar, last before the Dalton minimum, which was very long in duration, was also enriched with several new sunspot positions from this project. The possible splitting into two cycles is not ruled out by the new data, although a significance test remains to be done. The funding of this project also included the complete digitization of the observations by Honoré Flaugergues, France, which are now publicly available. All this work contributed to a comprehensive overview of historical sunspot observations, in particular those with drawings or other positional information, which the author wrote together with José Vaquero from Mérida, Spain, and which was published in 2020 in Living Reviews of Solar Physics.
Projektbezogene Publikationen (Auswahl)
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Sunspot Observations Made by Hallaschka During the Dalton Minimum. Solar Physics, 293(7).
Carrasco, V. M. S.; Vaquero, J. M.; Arlt, R. & Gallego, M. C.
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Christian Horrebow’s Sunspot Observations – I. Life and Published Writings. Solar Physics, 294(6).
Jørgensen, Carsten Sønderskov; Karoff, Christoffer; Senthamizh, Pavai V. & Arlt, Rainer
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Christian Horrebow’s Sunspot Observations – II. Construction of a Record of Sunspot Positions. Solar Physics, 294(6).
Karoff, Christoffer; Jørgensen, Carsten Sønderskov; Senthamizh, Pavai V. & Arlt, Rainer
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Sunspot Observations by Barnaba Oriani (1778 – 1779). Solar Physics, 295(6).
Nogales, J. M.; Carrasco, V. M. S.; Arlt, R.; Domínguez-Castro, F. & Vaquero, J. M.
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Thaddäus Derfflinger’s Sunspot Observations during 1802–1824: A Primary Reference to Understand the Dalton Minimum. The Astrophysical Journal, 890(2), 98.
Hayakawa, Hisashi; Besser, Bruno P.; Iju, Tomoya; Arlt, Rainer; Uneme, Shoma; Imada, Shinsuke; Bourdin, Philippe-A. & Kraml, Amand
