Studies of synoptic solar activity using Kodaikanal Ca K data

Abstract

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.