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  Analysis of full-disc Ca II K spectroheliograms III. Plage area composite series covering 1892–2019

Chatzistergos, T., Ermolli, I., Krivova, N. A., Solanki, S. K., Banerjee, D., Barata, T., et al. (2020). Analysis of full-disc Ca II K spectroheliograms III. Plage area composite series covering 1892–2019. Astronomy and Astrophysics, 639: A88. doi:10.1051/0004-6361/202037746.

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Chatzistergos, Theodosios1, Author           
Ermolli, Ilaria, Author
Krivova, Natalie A.1, Author           
Solanki, Sami K.1, Author           
Banerjee, Dipankar, Author
Barata, Teresa, Author
Belik, Marcel, Author
Gafeira, Ricardo, Author
Garcia, Adriana, Author
Hanaoka, Yoichiro, Author
Hegde, Manjunath, Author
Klimeš, Jan, Author
Korokhin, Viktor V., Author
Lourenço, Ana, Author
Malherbe, Jean-Marie, Author
Marchenko, Gennady P., Author
Peixinho, Nuno, Author
Sakurai, Takashi, Author
Tlatov, Andrey G., Author
1Department Sun and Heliosphere, Max Planck Institute for Solar System Research, Max Planck Society, ou_1832289              


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 Abstract: Context. Studies of long-term solar activity and variability require knowledge of the past evolution of the solar surface magnetism. The archives of full-disc Ca II K observations that have been performed more or less regularly at various sites since 1892 can serve as an important source of such information.

Aims. We derive the plage area evolution over the last 12 solar cycles by employing data from all Ca II K archives that are publicly available in digital form, including several as-yet-unexplored Ca II K archives.

Methods. We analysed more than 290 000 full-disc Ca II K observations from 43 datasets spanning the period between 1892–2019. All images were consistently processed with an automatic procedure that performs the photometric calibration (if needed) and the limb-darkening compensation. The processing also accounts for artefacts affecting many of the images, including some very specific artefacts, such as bright arcs found in Kyoto and Yerkes data. Our employed methods have previously been tested and evaluated on synthetic data and found to be more accurate than other methods used in the literature to treat a subset of the data analysed here.

Results. We produced a plage area time-series from each analysed dataset. We found that the differences between the plage areas derived from individual archives are mainly due to the differences in the central wavelength and the bandpass used to acquire the data at the various sites. We empirically cross-calibrated and combined the results obtained from each dataset to produce a composite series of plage areas. The ’backbone’ approach was used to bridge the series together. We have also shown that the selection of the backbone series has little effect on the final composite of the plage area. We quantified the uncertainty of determining the plage areas with our processing due to shifts in the central wavelength and found it to be less than 0.01 in fraction of the solar disc for the average conditions found on historical data. We also found the variable seeing conditions during the observations to slightly increase the plage areas during the activity maxima.

Conclusions. We provide the most complete so far time series of plage areas based on corrected and calibrated historical and modern Ca II K images. Consistent plage areas are now available on 88% of all days from 1892 onwards and on 98% from 1907 onwards.


Language(s): eng - English
 Dates: 2020
 Publication Status: Published online
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1051/0004-6361/202037746
 Degree: -



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Source 1

Title: Astronomy and Astrophysics
  Other : Astron. Astrophys.
Source Genre: Journal
Publ. Info: Les Ulis Cedex A France : EDP Sciences
Pages: 22 Volume / Issue: 639 Sequence Number: A88 Start / End Page: - Identifier: ISSN: 1432-0746
ISSN: 0004-6361
CoNE: https://pure.mpg.de/cone/journals/resource/954922828219_1