A Method for Characterizing Rotation Rates in the Soft X-Ray Corona

• Published in: Solar physics Vol. 189; no. 2; pp. 271 - 288
• Main Authors: Weber, MA, Acton, L W, Alexander, D, Kubo, S, Hara, H
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Nature B.V 01.11.1999
• Subjects: Solar flares; Solar physics; Sun
• ISSN: 0038-0938; 1573-093X
• DOI: 10.1023/A:1005243924098

Differential rotation rates of soft X-ray features in the solar corona are quantified by a method of harmonic filtering using the Lomb-Scargle periodogram. This approach leads reasonably to a quantitative discrimination between uncertainty estimates and spectral leakage of the fundamental rotation frequency due to the presence of multiple rotating tracers. Mean rotation rates as a function of latitude and year are calculated for the years 1992-1997 (roughly the declining phase of the last solar activity cycle). The corona 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 the relative uncertainties with which a `mean' rotation rate can be measured. The results are compared with autocorrelation estimates and found to agree within 1σ.[PUBLICATION ABSTRACT]