Solar Observations by Angelo Secchi. I. Digitization of Original Documents and Analysis of Group Numbers over the Period of 1853–1878

Ermolli, I.; Chatzistergos, T.; Giorgi, F.; Carrasco, V. M. S.; Aparicio, A. J. P.; Chinnici, I.

doi:10.3847/1538-4365/ad0886

Cited by 6 publications

(1 citation statement)

References 93 publications

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“…Janssen (1869) and Lockyer & Frankland The filament area butterfly diagram is available at the CDS via anonymous ftp to cdsarc.cds.unistra.fr (130.79.128.5) or via https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/ 680/A15 (1869) were the first to observe on-disc solar features in Hα. In the late 1800s, Secchi (Secchi 1871) and Tacchini (Tacchini 1872) made daily observations in the Hα line (Bocchino 1933;Ermolli & Ferrucci 2021;Ermolli et al 2023), and even though these were regular observations, they were merely visual inspections and reported in drawings. At that time, Hα observations were not common, and it was not before the invention of the spectroheliograph (hereafter SHG, Hale 1904) and the daily use of photography that they could be explored more widely and systematically.…”

Section: Introductionmentioning

confidence: 99%

Analysis of full-disc Hαobservations: Carrington maps and filament properties in 1909–2022

Chatzistergos,

Ermolli,

Banerjee

et al. 2023

A&A

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Context.Full-disc observations of the Sun in the Hαline provide information about the solar chromosphere, and in particular, about the filaments, which are dark and elongated features that lie along magnetic field polarity-inversion lines. This makes them important for studies of solar magnetism. Because full-disc Hαobservations have been performed at various sites since the second half of the 19th century, with regular photographic data having started at the beginning of the 20th century, they are an invaluable source of information on past solar magnetism.Aims.We derive accurate information about filaments from historical and modern full-disc Hαobservations.Methods.We consistently processed observations from 15 Hαarchives spanning 1909–2022. The analysed datasets include long-running ones such as those from Meudon and Kodaikanal, but also previously unexplored datasets such as those from Arcetri, Boulder, Larissa, and Upice. Our data processing includes photometric calibration of the data stored on photographic plates, the compensation for limb-darkening, and the orientation of the data to align solar north at the top of the images. We also constructed Carrington maps from the calibrated Hαimages.Results.We find that filament areas, similar to plage areas in Ca IIK data, are affected by the bandwidth of the observation. Thus, a cross calibration of the filament areas derived from different archives is needed. We produced a composite of filament areas from individual archives by scaling all of them to the Meudon series. Our composite butterfly diagram very distinctly shows the common features of filament evolution, that is, the poleward migration as well as a decrease in the mean latitude of filaments as the cycle progresses. We also find that during activity maxima, filaments cover ∼1% of the solar surface on average. The change in the amplitude of cycles in filament areas is weaker than in sunspot and plage areas.Conclusions.Analysis of Hαdata for archives with contemporaneous Ca IIK observations allowed us to identify and verify archive inconsistencies, which also have implications for reconstructions of past solar magnetism and irradiance from Ca IIK data.

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Section: Introductionmentioning

confidence: 99%

Analysis of full-disc Hαobservations: Carrington maps and filament properties in 1909–2022

Chatzistergos,

Ermolli,

Banerjee

et al. 2023

A&A

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Rudolf Wolf to Alfred Wolfer: The Transfer of the Reference Observer in the International Sunspot Number Series (1876–1893)

Bhattacharya,

Lefèvre,

Chatzistergos

et al. 2024

Sol Phys

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In 1876 Alfred Wolfer started observing the Sun and recording properties of sunspots alongside Rudolf Wolf. Their observations became the basis for the construction of the Sunspot Number series. After Wolf's death in 1893, Wolfer became the primary observer for the Sunspot Number series. Even though the observations of Wolf and Wolfer had an overlap of almost 17 years (1876-1893), this shift of primary observer S. Bhattacharya

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A Discussion of Implausible Total Solar-Irradiance Variations Since 1700

Chatzistergos

2024

Sol Phys

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The Sun plays a role in influencing Earth’s climate, making it important to have accurate information about variations in the Sun’s radiative output. Models are used to recover total solar-irradiance (TSI) variations in the past when direct space-based measurements are not available. One of the most cryptic such TSI reconstructions is the one by (J. Geophys. Res. 98, 18, 1993, HS93). The rather vague description of the model methodology, the arbitrary selection of solar indices it employs, and the short overlap between the HS93 series and directly measured TSI values has hindered any evaluation of the performance of this model to this day. Here, we aim at rectifying this by updating the HS93 model with new input data. In this way we are also contributing in the discussion on the possible long-term changes in solar irradiance.We find that the analysis by HS93 included a number of erroneous processing steps that led to an artificial increasing trend towards the end of the reconstructed TSI series as well as shifting the peak of the TSI in the mid-twentieth century back in time by about 11 years. Furthermore, by using direct measurements of the TSI we determined that the free parameter of the model, the magnitude of variations (here defined as percentage variations of the difference between the maximum to minimum values), is optimal when it is minimised (being ≤0.05%). This is in stark contrast to the high magnitude of variations, of 0.25%, that was imposed by HS93. However, our result is consistent with more recent estimates, such as those from the Spectral And Total Irradiance REconstruction (SATIRE) model and Naval Research Laboratory TSI (NRLTSI), which were used by the Intergovernmental Panel on Climate Change (IPCC). Overall, we find that the previously reported agreement of the HS93 TSI series to temperature on Earth was purely due to improper analysis and artefacts of the processing.

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Solar Observations by Angelo Secchi. I. Digitization of Original Documents and Analysis of Group Numbers over the Period of 1853–1878

Cited by 6 publications

References 93 publications

Analysis of full-disc Hαobservations: Carrington maps and filament properties in 1909–2022

Analysis of full-disc Hαobservations: Carrington maps and filament properties in 1909–2022

Rudolf Wolf to Alfred Wolfer: The Transfer of the Reference Observer in the International Sunspot Number Series (1876–1893)

A Discussion of Implausible Total Solar-Irradiance Variations Since 1700

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