Rome Precision Solar Photometric Telescope: precision solar full-disk photometry during solar cycles 23–25

Ermolli, I.; Giorgi, F.; Chatzistergos, Theodosios

doi:10.3389/fspas.2022.1042740

Cited by 9 publications

(5 citation statements)

References 67 publications

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“…Originally developed to analyse Ca ii K data, this method can be applied to consistently process observations from multiple archives and in different spectral bands. In addition to 43 Ca ii K datasets (Chatzistergos et al 2020b), it has already been successfully applied to data over four continuum intervals (Chatzistergos et al 2019a(Chatzistergos et al , 2020cErmolli et al 2022) and provisionally to a small sample of Hα images from the Kanzelhöhe observatory (Asvestari et al 2021).…”

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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“…We find all three Ca II K data sets to result in differential rotations that are indeed faster than the one found for the photosphere by tracing sunspots (Jha et al 2021). Additionally, it is crucial to acknowledge that, although the central wavelength of Ca II K filter for all these observatories is the same, they have different pass bands, e.g., KoSO: 0.05 nm (Priyal et al 2014), Meudon: 0.015 nm (Malherbe & Dalmasse 2019), and Rome/ PSPT: 0.25 nm (Ermolli et al 1998(Ermolli et al , 2022. Furthermore, KoSO and MWO data are spectroheliograms, while Rome/PSPT are filtergrams; thus, the shape of the pass bands might also differ.…”

Section: Comparison With Other Observatoriesmentioning

confidence: 96%

“…To test the robustness of our algorithm and to ensure that the result that we are getting is not an artifact of the data, we implemented it on the Ca II K data obtained at Meudon (Malherbe & Dalmasse 2019) and Rome/PSPT (Ermolli et al 1998(Ermolli et al , 2022 for the period of 2000-2002, which is close to the solar maximum and have significant plage regions. We applied the same process to determine the chromospheric rotation in the Meudon and Rome/PSPT data as we did for the KoSO ones.…”

Section: Comparison With Other Observatoriesmentioning

confidence: 99%

Differential Rotation of the Solar Chromosphere: A Century-long Perspective from Kodaikanal Solar Observatory Ca ii K Data

Mishra,

Routh,

Jha

et al. 2024

ApJ

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Chromospheric differential rotation is a key component in comprehending the atmospheric coupling between the chromosphere and the photosphere at different phases of the solar cycle. In this study, we therefore utilize the newly calibrated multidecadal Ca ii K spectroheliograms (1907–2007) from the Kodaikanal Solar Observatory (KoSO) to investigate the differential rotation of the solar chromosphere using the technique of image cross-correlation. Our analysis yields the chromospheric differential rotation rate Ω(θ) = (14.61 ± 0.04–2.18 ± 0.37 sin 2 θ − 1.10 ± 0.61 sin 4 θ ) ° day−1. These results suggest the chromospheric plages exhibit an equatorial rotation rate 1.59% faster than the photosphere when compared with the differential rotation rate measured using sunspots and also a smaller latitudinal gradient compared to the same. To compare our results to those from other observatories, we have applied our method on a small sample of Ca ii K data from Rome, Meudon, and Mount Wilson observatories, which support our findings from KoSO data. Additionally, we have not found any significant north–south asymmetry or any systematic variation in chromospheric differential rotation over the last century.

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“…These studies are particularly important to ascertain the ability of Ca ii K data to be used for accurate irradiance reconstructions. Since some CCD-based Ca ii K archives, such as those from Rome/PSPT (precision solar photometric telescope; Ermolli et al 2022) and San Fernando (Chapman et al 1997), have long and consistent observations they can also be used to assess the cycle minimum to minimum trend in TSI, thus avoiding degradation effects of satellite measurements or cross-calibration issues of different direct TSI series. Chatzistergos et al (2020a) used Rome/PSPT data to reconstruct solar irradiance variations back to 1996 with an empirical model based on the integrated intensity in Ca ii K and a continuum interval at the blue part of the spectrum (409.2 nm), following the approach by Chapman et al (2012Chapman et al ( , 2013.…”

Section: Ca II K Observationsmentioning

confidence: 99%

Long-term changes in solar activity and irradiance

Chatzistergos¹,

Krivova²,

Yeo³

2023

Preprint

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The Sun is the main energy source to Earth, and understanding its variability is of direct relevance to climate studies. Measurements of total solar irradiance (TSI) exist since 1978, but this is too short compared to climate-relevant time scales. Coming from a number of different instruments, these measurements require a cross-calibration, which is not straightforward, and thus several composite records have been created. All of them suggest a marginally decreasing trend since 1996. Most composites also feature a weak decrease over the entire period of observations, which is also seen in observations of the solar surface magnetic field and is further supported by Ca ii K data. Some inconsistencies, however, remain and overall the magnitude and even the presence of the long-term trend remain uncertain. Different models have been developed, which are used to understand the irradiance variability over the satellite period and to extend the records of solar irradiance back in time. Differing in their methodologies, all models require proxies of solar magnetic activity as input. The most widely used proxies are sunspot records and cosmogenic isotope data on centennial and millennial time scale, respectively. None of this, however, offers a sufficiently good, independent description of the long-term evolution of faculae and network responsible for solar brightening. This leads to significant uncertainties in the amplitude of the long-term changes in solar irradiance. Here we review recent efforts to improve irradiance reconstructions on time scales longer than the solar cycle and to reduce the existing uncertainty in the magnitude of the long-term variability. In particular, we highlight the potential of using 3D magnetohydrodynamical simulations of the solar atmosphere as input to more physical irradiance models and of historical full-disc Ca ii K observations encrypting direct facular information back to 1892.

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Rome Precision Solar Photometric Telescope: precision solar full-disk photometry during solar cycles 23–25

Cited by 9 publications

References 67 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

Differential Rotation of the Solar Chromosphere: A Century-long Perspective from Kodaikanal Solar Observatory Ca ii K Data

Long-term changes in solar activity and irradiance

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