Sunspot group tilt angles from drawings for cycles 19-24

Abstract

The tilt angle of a sunspot group is a critical quantity in the surface transport of magnetic flux and the solar dynamo. To contribute long-term databases of the tilt angle, we developed an IDL routine, which allows the user to interactively select and measure sunspot positions and areas on the solar disc. We measured the tilt angles of sunspot groups for solar cycles 19-24 (1954.6-2017.8), using the sunspot drawing database of Kandilli Observatory. The method is similar to that used in the discontinued Mt. Wilson and Kodaikanal databases, with the exception that sunspot groups were identified manually, which has improved the accuracy of the resulting tilt angles. We obtained cycle averages of the tilt angle and compared them with the values from other datasets, keeping the same group selection criteria. We conclude that the previously reported anti-correlation with the cycle strength needs further investigation.

arXiv comment4 pages, 3 figures, IAU Symp. 340: Long-Term Datasets for the Understanding of Solar and Stellar Magnetic Cycles

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Cited by in corpus (4)

• Solar cycle prediction
• Sunspot tilt angles revisited: Dependence on the solar cycle strength
• Towards an algebraic method of solar cycle prediction II. Reducing the need for detailed input data with ARDoR
• Low-Latitude Sunspot Group Tilt Angles in 15-24 Activity Cycles