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Title: Long-term variations in the intensity of plages and networks as observed in Kodaikanal Ca-K digitized data
Authors: Priyal, M
Singh, J
Ravindra, B
Kameshwaran Rathina, Somasundaram
Keywords: Sun;Chromosphere;Active and quiet;Intensity variations;Solar cycle
Issue Date: Jul-2017
Publisher: Springer
Citation: Solar Physics, Vol. 292, No. 7, 85
Abstract: In our previous article (Priyal et al. in Solar Phys.289, 127, 2014) we have discussed the details of observations and methodology adopted to analyze the Ca-K spectroheliograms obtained at the Kodaikanal Observatory (KO) to study the variation of Ca-K plage areas, enhanced network (EN), and active network (AN) for Solar Cycles, namely 19, 20, and 21. Now, we have derived the areas of chromospheric features using KO Ca-K spectroheliograms to study the long-term variations of Solar Cycles 14 to 21. The comparison of the derived plage areas from the data obtained at the KO observatory for the period 1906 – 1985 with that of MWO, NSO for the period 1965 – 2002, earlier measurements made by Tlatov, Pevtsov, and Singh (Solar Phys.255, 239, 2009) for KO data, and the SIDC sunspot numbers shows a good correlation. The uniformity of the data obtained with the same instrument remaining with the same specifications provided a unique opportunity to study long-term intensity variations in plages and network regions. Therefore, we have investigated the variation of the intensity contrast of these features with time at a temporal resolution of six months assuming that the quiet-background chromosphere remains unchanged during the period 1906 – 2005 and found that the average intensity of the AN, representing the changes in small-scale activity over solar surface, varies with solar cycle being less during the minimum phase. In addition, the average intensity of plages and EN varies with a very long period having a maximum value during Solar Cycle 19, which was the strongest solar cycle of twentieth century.
Description: Restricted Access
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ISSN: 0250-6335
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Appears in Collections:IIAP Publications

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