Indirect comparison of Debrecen and Greenwich daily sums of sunspot areas

Baranyi, Tünde and Király, Sándor and Coffey, H. E. (2013) Indirect comparison of Debrecen and Greenwich daily sums of sunspot areas. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 434 (2). pp. 1713-1720. ISSN 0035-8711

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Abstract

Sunspot area data play an important role in the studies of solar activity and its long- term variations. In order to reveal real long-term solar variations precise homogeneous sunspot area databases should be used. However, the measured areas may be bur- dened with systematic deviations, which may vary in time. Thus, there is a need to investigate the long-term variation of sunspot area datasets and to determine the time- dependent cross-calibration factors. In this study, we investigate the time-dependent differences between the available long-term sunspot databases. Using the results, we estimate the correction factor to calibrate the corrected daily sunspot areas of Debre- cen Photoheliographic Data (DPD) to the same data of Greenwich Photoheliographic Results (GPR) by using the overlapping Kislovodsk and Pulkovo data. We give the correction factor as GP R = 1.08(±0.11) ∗ DP D.

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