Network and plage indices from Kodaikanal Ca-K data

Raju, K. P.; Singh, Jagdev

doi:10.1088/1674-4527/14/2/010

Cited by 6 publications

(4 citation statements)

References 12 publications

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“…Simon and Leighton (1964) noticed a spatial correspondence between the chromospheric network in Ca II K observations and boundaries of supergranular cells seen in the photosphere. This triggered a series of studies of supergranular parameters by using Ca II K observations (Sotnikova, 1978;Singh and Bappu, 1981;Raghavan, 1983;Münzer et al, 1989;Kariyappa and Sivaraman, 1994;Hagenaar et al, 1997;Berrilli et al, 1998;Berrilli et al, 1999;Ermolli et al, 1998a;Ermolli et al, 1998b;Pietropaolo and Ermolli, 1998;Raju et al, 1998;Goldbaum et al, 2009;Raju and Singh, 2014;Raju, 2020;McIntosh et al, 2011;Chatterjee et al, 2017b;Mandal et al, 2017b;Rajani et al, 2022). The cell sizes determined from Ca II K data were in general smaller than the diameter of the supergranular cells in the photosphere reported by Simon and Leighton (1964, about 32 Mm).…”

Section: Network Cell Characteristicsmentioning

confidence: 99%

Full-disc Ca ii K observations—A window to past solar magnetism

Chatzistergos

Krivova

Ermolli

2022

Front. Astron. Space Sci.

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Full-disc observations of the Sun in the Ca ii K line provide one of the longest collections of solar data. First such observations were made in 1892 and since then various sites around the world have carried out regular observations, with Kodaikanal, Meudon, Mt Wilson, and Coimbra being some of the most prominent ones. By now, Ca ii K observations from over 40 different sites allow an almost complete daily coverage of the last century. Ca ii K images provide direct information on plage and network regions on the Sun and, through their connection to solar surface magnetic field, offer an excellent opportunity to study solar magnetism over more than a century. This makes them also extremely important, among others, for solar irradiance reconstructions and studies of the solar influence on Earth’s climate. However, these data also suffer from numerous issues, which for a long time have hampered their analysis. Without properly addressing these issues, Ca ii K data cannot be used to their full potential. Here, we first provide an overview of the currently known Ca ii K data archives and sources of the inhomogeneities in the data, before discussing existing processing techniques, followed by a recap of the main results derived with such data so far.

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Section: Network Cell Characteristicsmentioning

confidence: 99%

Full-disc Ca ii K observations—A window to past solar magnetism

Chatzistergos

Krivova

Ermolli

2022

Front. Astron. Space Sci.

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“…The data for faculae and Ca II K-line (393.37 nm) are based on daily synoptic full-disk images obtained by photoelectric photometry of sunspots at the San Fernando Observatory (SFO) ¶ . The plage and Ca II K-flux observations were taken from the Kodaikanal Data (KKL) (Singh et al 2012, Raju and Singh 2014, Priyal et al 2014. However, we preferred using the Ca II K-line images from SFO to compare with the faculae observations from the same observatory.…”

Section: Data Descriptionmentioning

confidence: 99%

“…The intensity calibration of Ca II K-line images, however, is very difficult because of the contributions from the quiet Sun limb darkening curve. In addition to this, observations near the core of the ionized Ca II K-line (393.37 nm) are one of the most effective tools in investigating the morphology and evolution of both plages and chromospheric magnetic network (Raju and Singh 2014).…”

Section: Introductionmentioning

confidence: 99%

Temporal variations of different solar activity indices through the solar cycles 21-23

et al. 2017

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Here, we compare the sunspot counts and the number of sunspot groups (SGs) with variations of total solar irradiance (TSI), magnetic activity, Ca II K-flux, faculae and plage areas. We applied a time series method for extracting the data over the descending phases of solar activity cycles (SACs) 21, 22 and 23, and the ascending phases 22 and 23. Our results suggest that there is a strong correlation between solar activity indices and the changes in small (A, B, C and H-modified Zurich Classification) and large (D, E and F) SGs. This somewhat unexpected finding suggests that plage regions substantially decreased in spite of the higher number of large SGs in SAC 23 while the Ca II K-flux did not decrease by a large amount nor was it comparable with SAC 22 and relates with C and DEF type SGs. In addition to this, the increase of facular areas which are influenced by large SGs, caused a small percentage decrease in TSI while the decrement of plage areas triggered a higher decrease in the magnetic field flux. Our results thus reveal the potential of such a detailed comparison of the SG analysis with solar activity indices for better understanding and predicting future trends in the SACs.

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“…The Ca ii K line at 3934Å is a strong chromospheric line. The Ca images are dominated by chromospheric network and plages (Raju & Singh 2014). It is well known that the chromospheric network outlines supergranular cells which play an important role in maintaining solar cycle through magnetic flux dispersal along its boundaries.…”

Section: Introductionmentioning

confidence: 99%

Studies of synoptic solar activity using Kodaikanal Ca K data

Raju

2016

Proc. IAU

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The chromospheric network, the bright emission network seen in the chromospheric lines such as Ca ii K and Hα, outline the supergranulation cells. The Ca images are dominated by the chromospheric network and plages which are good indicators of solar activity. Further, the Ca line is a good proxy to the UV irradiance which is particularly useful in the pre-satellite era where UV measurements are not available. The Ca spectroheliograms of the Sun from Kodaikanal have a data span of about 100 years and covers over 9 solar cycles. The archival data is now available in the digitized form. Programs have been developed to obtain the activity indices and the length scales of the chromospheric network from the data. The preliminary results from the analysis are reported here. It is shown that the Ca ii K intensity and the network boundary width are dependent on the solar cycle.

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Network and plage indices from Kodaikanal Ca-K data

Cited by 6 publications

References 12 publications

Full-disc Ca ii K observations—A window to past solar magnetism

Full-disc Ca ii K observations—A window to past solar magnetism

Temporal variations of different solar activity indices through the solar cycles 21-23

Studies of synoptic solar activity using Kodaikanal Ca K data

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