A method for characterizing rotation rates in the soft X-ray corona

Differential rotation rates of soft X-ray features in the solar corona are quantified by a method of harmonic filtering using the Lomb-Scargle periodo gram. This approach leads reasonably to a quantitative discrimination betwe en uncertainty estimates and spectral leakage of the fundamental rotation f requency due to the presence of multiple rotating tracers. Mean rotation ra tes as a function of latitude and year are calculated for the years 1992-19 97 (roughly the declining phase of the last solar activity cycle). The coro na is found to have a small but measurable latitudinal gradient in rotation rate. The presence of multiple features places a lower bound of 1-2% on th e relative uncertainties with which a 'mean' rotation rate can be measured. The results are compared with autocorrelation estimates and found to agree within 1 sigma.