PATTERNS OF VARIATION AMONG SUN-LIKE STARS

We examine the patterns of variation among a sample of 35 stars that i ncludes the Sun, particularly on the timescale of the 11 yr solar acti vity cycle. Our investigation uses contemporaneous photometric and chr omospheric HK emission time series measurements from the Lowell and Mo unt Wilson Observatories, and comparable solar data. We find that the photometric and HK variability of the stars in our sample can be relat ed to their average level of chromospheric activity by power laws. The photometric variability of the Sun may be somewhat subdued for its av erage activity level. We find that the younger, more active stars in o ur sample tend to become fainter as their HK emission increases, where as the older, less active stars tend to become brighter as their HK em ission increases, as the Sun does during its activity cycle.