Author : Sree Raksha Gupta A R 1
Date of Publication :22nd June 2018
Abstract: The long-term synoptic observations in the resonance line of Ca-II K (singly ionized calcium) provides the basis for a fundamental database to a variety of retrospective analysis of the state of solar magnetism. The Ca-II K observations in Kodaikanal Solar Observatory (KSO) is extremely important as it provides a unique dataset in the world for the study of chromospheric activity and its variability as a function of the well-known solar magnetic 11-year cycle. It is known that Ca-II Kline is a very good indicator of chromospheric activity and variability of the Sun and Sun-like stars. The spectroheliograms will be used as a proxy for magnetic elements of the chromosphere i.e., the intensity of the chromospheric features is well correlated with the strength of the magnetic field associated with them. That means there is the one-to-one correspondence between the chromospheric emission features with underlying photospheric magnetic elements. In this paper, the digitized and calibrated Ca-II K spectroheliograms observed at KSO in the period 1917 is used for analysis. The paper proposed segments of the plages and derives their intensity and area. This helps in the estimation of the total contribution of plages to the variability of the chromosphere. Various image processing techniques for this analysis are implemented using MATLAB 2016a
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