Cyclic and Secular Activity Changes in Solar Analog Stars

Jeffrey C. Hall [jch@lowell.edu] and G. W. Lockwood, Lowell Observatory, Flagstaff, Arizona; and Sallie L. Baliunas (CfA).

            We present the most recent Ca II H&K observations of cyclic and long-term variability in the Sun and selected solar analogs, using data from the Solar-Stellar Spectrograph (SSS) project and the Mount Wilson Observatory HK project. We discuss trends in evolution of cycle amplitudes and activity levels at cycle minima, as well as the distribution of activity levels among the closest solar analogs, and discuss their relevance as stellar proxies for assessing the magnitude of long-term solar irradiance changes.