Solar observatory Einstein Tower: Data release of the digitized solar full‐disk photographic plate archive

Pal, Partha Sarathi; Verma, M.; Rendtel, J.; Manrique, S. J. González; Enke, H.

doi:10.1002/asna.202013791

Cited by 6 publications

(3 citation statements)

References 37 publications

(43 reference statements)

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“…accounting for sunspots using alternative data, such as white light observations (e.g. Willis et al, 2016;Pal et al, 2020), could allow irradiance reconstructions from properly calibrated historical Ca II K observations, e.g. those from Meudon (Malherbe & Dalmasse, 2019) or Kodaikanal (Chatzistergos et al, 2019c) observatories, to extend the reconstruction back to 1892 (Chatzistergos et al, 2020a).…”

Section: Discussionmentioning

confidence: 99%

Modelling solar irradiance from ground-based photometric observations

Chatzistergos

Ermolli

Giorgi

et al. 2020

J. Space Weather Space Clim.

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Total solar irradiance (TSI) has been monitored from space since 1978, i.e. for about four solar cycles. The measurements show a prominent variability in phase with the solar cycle, as well as fluctuations on timescales shorter than a few days. However, the measurements were done by multiple and usually relatively short-lived missions. The different absolute calibrations of the individual instruments and the unaccounted for instrumental trends make estimates of the possible long-term trend in the TSI highly uncertain. Furthermore, both the variability and the uncertainty are strongly wavelength-dependent. While the variability in the UV irradiance is clearly in-phase with the solar cycle, the phase of the variability in the visible range has been debated. In this paper, we aim at getting an insight into the long-term trend of TSI since 1996 and the phase of the solar irradiance variations in the visible part of the spectrum. We use independent ground-based full-disc photometric observations in Ca II K and continuum from the Rome and San Fernando observatories to compute the TSI since 1996. We follow the empirical San Fernando approach based on the photometric sum index. We find a weak declining trend in the TSI of $ {-7.8}_{-0.8}^{+4.9}\times 1{0}^{-3}$ Wm−2 y−1 between the 1996 and 2008 activity minima, while between 2008 and 2019 the reconstructed TSI shows no trend to a marginally decreasing (but statistically insignificant) trend of $ {-0.1}_{-0.02}^{+0.25}\times 1{0}^{-3}$ Wm−2 y−1. The reference TSI series used for the reconstruction does not significantly affect the determined trend. The variation in the blue continuum (409.2 nm) is rather flat, while the variation in the red continuum (607.1 nm) is marginally in anti-phase, although this result is extremely sensitive to the accurate assessment of the quiet Sun level in the images. These results provide further insights into the long-term variation of the TSI. The amplitude of the variations in the visible is below the uncertainties of the processing, which prevents an assessment of the phase of the variations.

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Section: Discussionmentioning

confidence: 99%

Modelling solar irradiance from ground-based photometric observations

Chatzistergos

Ermolli

Giorgi

et al. 2020

J. Space Weather Space Clim.

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show abstract

Section: Discussionmentioning

confidence: 99%

Modelling solar irradiance from ground-based photometric observations

Chatzistergos,

Ermolli,

Giorgi

et al. 2020

Preprint

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Total solar irradiance has been monitored from space since 1978, i.e. for about four solar cycles. The measurements show a prominent variability in phase with the solar cycle, as well as fluctuations on timescales shorter than a few days. However, the measurements were done by multiple and usually relatively short-lived missions. The different absolute calibrations of the individual instruments and the unaccounted for instrumental trends make estimates of the possible long-term trend in the total solar irradiance highly uncertain. Furthermore, both the variability and the uncertainty are strongly wavelength-dependent. While the variability in the UV irradiance is clearly in-phase with the solar cycle, the phase of the variability in the visible range has been debated. In this paper, we aim at getting an insight into the long-term trend of total solar irradiance since 1996 and the phase of the solar irradiance variations in the visible part of the spectrum. We use independent ground-based full-disc photometric observations in Ca II K and continuum from the Rome and San Fernando observatories to compute the total solar irradiance since 1996. We follow the empirical San Fernando approach based on the photometric sum index. We find a weak declining trend in the total solar irradiance of -7.8 +4.9 −0.8 × 10 −3 Wm −2 y −1 between the 1996 and 2008 activity minima, while between 2008 and 2019 the reconstructed TSI shows no trend to a marginally decreasing (but statistically insignificant) trend of -0.1 +0.25 −0.02 × 10 −3 Wm −2 y −1 . The reference TSI series used for the reconstruction does not significantly affect the determined trend. The variation in the blue continuum (409.2 nm) is rather flat, while the variation in the red continuum (607.1 nm) is marginally in anti-phase, although this result is extremely sensitive to the accurate assessment of the quiet Sun level in the images. These results provide further insights into the long-term variation of the total solar irradiance. The amplitude of the variations in the visible is below the uncertainties of the processing, which prevents an assessment of the phase of the variations.

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“…The McIntosh [1990] study showed the importance of context observations and large statistical samples in establishing the crucial characteristics of flare-productive regions. To this end, the digitization of such observations may expand this sample of observations as far back as the 18 th century [See Pal et al, 2020, for a non-exhaustive but informative review of digitization efforts]. Moreover, the study also showed that the association between flare-productivity and active region characteristics is statistical: even though it is clear that the most complex classes are associated with higher flaring rates, flares may occur in simpler regions irrespective of the phase of their evolution.…”

Section: Quantifying the White-light Morphology Of Active Regionsmentioning

confidence: 99%

The characteristics of flare- and CME-productive solar active regions

Kontogiannis¹

2023

Advances in Space Research

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Solar observatory Einstein Tower: Data release of the digitized solar full‐disk photographic plate archive

Cited by 6 publications

References 37 publications

Modelling solar irradiance from ground-based photometric observations

Modelling solar irradiance from ground-based photometric observations

Modelling solar irradiance from ground-based photometric observations

The characteristics of flare- and CME-productive solar active regions

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