  The characterization of solar surface differential rotation (SDR) from
disk-integrated chromospheric measurements has important implications for the
study of differential rotation and dynamo processes in other stars. Some
chromospheric lines, such as Ca II K, are very sensitive to the presence of
activity on the disk and are an ideal choice for investigating SDR in Sun-as-a
star observations. Past studies indicate that when the activity is low, the
determination of Sun's differential rotation from integrated-sunlight
measurements becomes uncertain. However, our study shows that using the proper
technique, SDR can be detected from these type of measurements even during
periods of extended solar minima. This paper describes results from the
analysis of the temporal variations of Ca II K line profiles observed by the
Integrated Sunlight Spectrometer (ISS) during the declining phase of Cycle 23
and the rising phase of Cycle 24, and discusses the signature of SDR in the
power spectra computed from time series of parameters derived from these
profiles. The described methodology is quite general, and could be applied to
photometric time series of other Main-Sequence stars for detecting differential
rotation.
