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Table 1

Summary description of the daily full-disc continuum intensity images and longitudinal magnetograms selected for this study.

Proportion of
Instrument No. of data days Period [year.month.day] period covered Image size [pixel] Pixel scale [arcsec] Spectral line

KP512 1371 1974.08.23 to 1993.04.04 0.20 2048 × 2048 1 Fe I 8688 Å
KPSPM 2055 1992.11.21 to 2003.09.21 0.52 1788 × 1788 1.14 Fe I 8688 Å
MDI 3941 1999.02.02 to 2010.12.24 0.91 1024 × 1024 1.98 Ni I 6768 Å
HMI 1128 2010.04.30 to 2013.05.31 1.00 4096 × 4096 0.504 Fe I 6173 Å

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