Sunspot Numbers and Areas from the Madrid Astronomical Observatory (1876 – 1986)
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The solar program of the Astronomical Observatory of Madrid started in 1876. Observations were made in this institution to determine sunspot numbers and areas for ten solar cycles. The program was completed in 1986 and the resulting data have been published in various Spanish scientific publications. Four periods of this program (with different observers and instruments) were identified with the aid of the interesting metadata that has been made available. In the present work, the published data were retrieved and digitized. Their subsequent analysis showed that most of these data could be considered reliable given their very high correlation with reference indices (international sunspot number, group sunspot number, and sunspot area). An abrupt change emerged in the sunspots/groups ratio in 1946, which lasted until 1972.
KeywordsSolar activity Sunspot area Sunspot number
We wish to acknowledge the assistance provided by the library and archive staff of the Centro Territorial de la AEMET (Badajoz, Spain), the Observatorio Astronómico de Madrid (Madrid, Spain), the Observatório Astronómico de Lisboa (Lisbon, Portugal), and the Real Observatorio de la Armada (San Fernando, Spain). J.M. Vaquero benefited from the impetus from participating in the Sunspot Number Workshops ( http://ssnworkshop.wikia.com/wiki/Home ). Support from the Junta de Extremadura (Research Group Grant No. GR10131), from the Ministerio de Economía y Competitividad of the Spanish Government (AYA2011-25945), and from the COST Action ES1005 TOSCA ( http://www.tosca-cost.eu ) is gratefully acknowledged.
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