Chromospheric CA II K-line variations in the sun as a star over a solar cycle

Abstract

The disk-averaged Ca II K profiles obtained at the Kodaikanal solar tower telescope for the period 1969-1984 are used to study the chromospheric variations in the sun as a star. The 1A index shows increases of 18 and 28 percent during the 20th and 21st cycles, respectively. The corresponding enhancements in the central intensity in the K line are 24 and 40 percent, respectively. The other K-line parameters, such as the intensity of K2 emission, K-line widths, and the V/R asymmetry, all show systematic variations over the solar cycle. Although the plage seems to be responsible for almost all the variations noticed, the participation of the bright points and the network may have to be taken into consideration to account fully for all the solar cycle-related changes.