aat Acta Astrophys. Tau. Acta Astrophysica Taurica 2712-925X Kiselev Nikolai Nikolaevich, Mosсow, settlement Moskovskii, Tat'yanin Park Str., 12, Moscow, Russia. RU 74 Research articles Comparison of the magnetic fields in solar active regions derived with different instruments Suleymanova Regina Crimean Astrophysical Observatory, Nauchny, 298409 23 06 2024 5 2 1 5 16 06 2024 Copyright (c) 2026 Suleymanova R. 2026 Regina Suleymanova The metadata for this submission is licensed under a Creative Commons Attribution 4.0 International License. Copyright and publishing rights for texts published in Acta Astrophysica Taurica is retained by the authors, with first publication rights granted to the journal.Texts are free to use with proper attribution and link to the licensing (Creative Commons Attribution 4.0 International).

The paper presents a comparison of the magnetic fluxes in active regions (ARs) measured with SOHO/MDI and SDO/HMI. The transition coefficients from HMI to MDI data are as follows: 1.46 for ARs observed within 10° of the central meridian and 1.29 for ARs observed at longitudes [−60°; −10°] and [10°; 60°]. The maximum magnetic field values in sunspots obtained in 2014 from SDO/HMI and with the ground-based telescope BST-2 at the Crimean Astrophysical Observatory of the Russian Academy of Sciences were compared using the orthogonal regression method. It is shown that the best agreement between data from the two instruments is achieved when comparing Crimean data with HMI data on the full field vector (correlation coefficient 0.71) rather than on its  longitudinal component (correlation coefficient 0.66). This conclusion indicates that the field measurements by the spectral line shift method (applied at BST-2) yield a value of the full field vector with the sign of its longitudinal component. The comparison results evidence for the possibility of using Crimean sunspot magnetic field data, which is particularly valuable for studying solar cycles prior to the space age.

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