Solar Optical Observations from Kodaikanal and from Eclipses

Abstract

From an analysis of a long series of Calcium K spectroheliograms taken at Kodaikanal, systematic changes in the sizes of supergranule cells have been found. The average cell size changes with the phase of solar cycle, being smaller at the maximum. Power spectral analysis of calcium plage areas indicates that chromospheric rotation rate at a fixed latitude varies over time scales ranging from the solar activity cycle down to about 2 years. The variation is of the order of 10% and is not correlated in different hemispheres.

The results of high resolution spectroscopy of the solar corona using multislit spectrograph at the total solar eclipses of 1980 and 1983 are also discussed. The line width measurements indicate that the turbulence might be a function of solar activity, being higher when the sun is more active. The line-of-sight velocities measurements show that there are no large scale localized differential mass motions in the corona and the solar corona co-rotates with the photospehric layers deeper down.