Long-term relationships between sunspots, Ca-plages and the ionosphere

KURIYAN, P. P.; Muralidharan, V.; Sampath, S.

doi:10.1016/s0021-9169(83)80034-8

Cited by 5 publications

(7 citation statements)

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“…Figure 15 shows scatter plots between the plage areas derived by us from the DS2 data and the various published series obtained from Kodaikanal observations. In particular we consider the series by Kuriyan, Muralidharan, and Sampath (1983) derived from the physical photographs, the series by Ermolli et al (2009b) and Tlatov, Pevtsov, and Singh (2009) from the DS1 data, and the series by Chatterjee, Banerjee, and Ravindra (2016), Priyal et al (2017), and Singh et al (2018) from the DS2 data. Note that the series by Kuriyan, Muralidharan, and Sampath (1983) and Tlatov, Pevtsov, and Singh (2009) are only available as annual values and most likely include different selections of observations.…”

Section: Results From Ds1 Ds2 and Rome/psptmentioning

confidence: 99%

Delving into the Historical Ca ii K Archive from the Kodaikanal Observatory: The Potential of the Most Recent Digitized Series

et al. 2019

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Full-disc Ca II K photographic observations of the Sun carry direct information as regards the evolution of solar-plage regions for more than a century and are therefore a unique dataset for solar-activity studies. For a long time Ca II K observations were barely explored, but recent digitizations of multiple archives have allowed their extensive analysis. However, various studies have reported diverse results partly due to the insufficient quality of the digitized data. Furthermore, inhomogeneities have been identified within the individual archives, which, at least partly, could be due to the digitization. As a result, some of the archives, e.g. that from the Kodaikanal observatory, were re-digitized. The results obtained by different authors who analyzed the data from the new digitization of the Kodaikanal archive differ from each other and from those derived from the old digitization. Since the data were processed and analyzed using different techniques, it is not clear, however, whether the differences are due to the digitization or the processing of the data. To understand the reasons for such discrepancies, we analyze here the data from the two most recent digitizations of this archive. We use the same techniques to consistently process the images from both archives and to derive the plage areas from them. Some issues have been identified in both digitizations, implying that they are intrinsic characteristics of the data. Moreover, errors in timing of the observations plague both digitizations. Overall, the most recent 16-bit digitization offers an improvement over the earlier 8-bit one. It also includes considerably more data and should be preferred.

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Section: Results From Ds1 Ds2 and Rome/psptmentioning

confidence: 99%

Delving into the Historical Ca ii K Archive from the Kodaikanal Observatory: The Potential of the Most Recent Digitized Series

et al. 2019

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“…There is a correlation between facular area and CaK plage area but this is not exact: in particular, the "rollover" in A f at the highest R is not seen in the plage area (Foukal, 1993). Nevertheless, multiple regressions between annual means of Slough foF2 and a combination of R and plage area have been made by Kuriyan, Muralidharan, and Sampath (1983).…”

Section: Discussionmentioning

confidence: 99%

“…There is a correlation between facular area and Ca K plage area, but this is not exact: in particular, the "rollover" in A f at the highest R is not seen in the plage area (Foukal, 1993). Nevertheless, multiple regressions between annual means of Slough foF2 and a combination of R and plage area have been made by Kuriyan, Muralidharan, and Sampath (1983). Because the Ca K plage area varies monotonically with R for annual means (Foukal, 1993), it should be possible to fit sunspot numbers with a polynomial in these foF2 data alone.…”

Section: Discussionmentioning

confidence: 99%

Tests of Sunspot Number Sequences: 1. Using Ionosonde Data

et al. 2016

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More than 70 years ago, it was recognised that ionospheric F2-layer critical frequencies [foF2] had a strong relationship to sunspot number. Using historic datasets from the Slough and Washington ionosondes, we evaluate the best statistical fits of foF2 to sunspot numbers (at each Universal Time [UT] separately) in order to search for drifts and abrupt changes in the fit residuals over Solar Cycles 17 -21. This test is carried out for the original composite of the Wolf/Zürich/International sunspot number [R], the new "backbone" group sunspot number [R BB ], and the proposed "corrected sunspot number" [R C ]. Polynomial fits are made both with and without allowance for the white-light facular area, which has been reported as being associated with cycle-to-cycle changes in the sunspot-number-foF2 relationship. Over the interval studied here, R, R BB , and R C largely differ in their allowance for the "Waldmeier discontinuity" around 1945 (the correction factor for which for R, R BB , and R C is, respectively, zero, effectively over 20 %, and explicitly 11.6 %). It is shown that for Solar Cycles 18 -21, all three sunspot data sequences perform well, but that the fit residuals are lowest and most uniform for R BB . We here use foF2 for those UTs for which R, R BB , and R C all give correlations exceeding 0.99 for intervals both before and after the Waldmeier discontinuity. The error introduced by the Waldmeier discontinuity causes R to underestimate the fitted values based on the foF2 data for 1932 -1945, but R BB overestimates them by almost the same factor, implying that the correction for the Waldmeier discontinuity inherent in R BB is too large by a factor of two. Fit residuals are smallest and most uniform for R C , and the ionospheric data support the optimum discontinuity multiplicative correction factor derived from the independent Royal Greenwich Observatory (RGO) sunspot group data for the same interval.Sunspot Number Recalibration

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“…We also considered the previously published Ca ii K plage area series by Kuriyan et al (1983), Foukal (1996Foukal ( , 2002, Ermolli et al (2009b), Tlatov et al (2009), Chatterjee et al (2016), Priyal et al (2017), Singh et al (2018), SGD 2 , as well as the Ca ii K emission index by Bertello et al (2010).…”

Section: Ca II K Plage Seriesmentioning

confidence: 99%

“…The processing and data selection vary considerably among the above published series (see Chatzistergos et al 2019b, for more details). For example, the series by Kuriyan et al (1983) was created by manually selecting the plage regions from the actual Ko photographs. Similarly, the SGD series includes areas determined manually from the physical photographs of the MM (06/194209/1979), MW (10/197909/1981), andBB (10/198111/1987) observatories.…”

Section: Ca II K Plage Seriesmentioning

confidence: 99%

Scrutinising the relationship between plage areas and sunspot areas and numbers

Chatzistergos

Ermolli

Krivova

et al. 2022

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Context. Studies and reconstructions of past solar activity require data on all magnetic regions on the surface of the Sun (i.e. on dark sunspots as well as bright faculaeplage and network). Such data are also important for understanding the magnetic activity and variability of the Sun and Sun-like stars. The longest available direct faculaeplage datasets are white-light facular and Ca ii K observations going back to 1874 and 1892, respectively. Prior to that time the only direct data available are for sunspots. Aims. We reassess the relationship between plage areas and sunspot records (areas and numbers) since 1892, to allow reconstructions of facularplage areas which can be employed for studies going further back in time to the period when solely sunspot observations are available. Methods. We use the plage areas derived from 38 consistently processed Ca ii K archives as well as the plage area composite based on these archives. The considered archives include both the well-known observatories (e.g. Coimbra, Kodaikanal, Meudon, Mt Wilson), and the less explored observatories (e.g. Kharkiv, Mees, and Upice). These data allow us to study the relationship between plage area and sunspot records (areas and number) over a period of 12 solar cycles and for dierent bandpasses. Results. We nd the relationship between plage and sunspot areas to be well represented by a power-law function; the relationship between the plage areas and the sunspot number is also best t with a power-law function. We further nd that the relationships depend on the bandwidth and the solar cycle strength. The reconstructions with a power-law relationship are in good agreement with the original plage area series, whereas employment of a cycle-strength-dependent relationship improves the reconstructions only marginally. We also estimate the error in the plage areas reconstructed from the sunspot areas or numbers. Performing the same analysis on other previously published plage area series, usually derived from a single archive with diverse processing techniques, returns dierent results when using dierent time series. This highlights the importance of applying a consistent processing to the various archives and demonstrates the uncertainties introduced by using previously published series for studies of past solar activity, including irradiance reconstructions. Conclusions. Our results have implications for past solar activity and irradiance reconstructions and for stellar activity studies, which sometimes assume a linear dependence between plage and sunspot areas.

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Long-term relationships between sunspots, Ca-plages and the ionosphere

Cited by 5 publications

References 1 publication

Delving into the Historical Ca ii K Archive from the Kodaikanal Observatory: The Potential of the Most Recent Digitized Series

Delving into the Historical Ca ii K Archive from the Kodaikanal Observatory: The Potential of the Most Recent Digitized Series

Tests of Sunspot Number Sequences: 1. Using Ionosonde Data

Scrutinising the relationship between plage areas and sunspot areas and numbers

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