Search for Short-Term Periodicities in the Sun's Surface Rotation: A Revisit

TL;DR

This study reexamines the Sun's surface rotation data, finding apparent short-term periodicities before 1996 likely due to measurement artifacts, and suggests the absence of these periodicities in more recent data indicates real differences in solar rotation behavior across cycles.

Contribution

The paper critically revisits previous claims of short-term periodicities in solar rotation, highlighting potential data artifacts and emphasizing the importance of data quality in solar cycle analysis.

Findings

Short-term periodicities were observed before 1996 but likely due to measurement artifacts.

No significant periodicities detected in data after 1995 with improved measurements.

Differences in solar activity phenomena between cycles 22 and 23 are evident.

Abstract

The power spectral analyses of the Sun's surface equatorial rotation rate determined from the Mt. Wilson daily Doppler velocity measurements during the period 3 December 1985 to 5 March 2007 suggests the existence of 7.6 year, 2.8 year, 1.47 year, 245 day, 182 day and 158 day periodicities in the surface equatorial rotation rate during the period before 1996. However, there is no variation of any kind in the more accurately measured data during the period after 1995. That is, the aforementioned periodicities in the data during the period before the year 1996 may be artifacts of the uncertainties of those data due to the frequent changes in the instrumentation of the Mt. Wilson spectrograph. On the other hand, the temporal behavior of most of the activity phenomena during cycles 22 (1986-1996) and 23 (after 1997) is considerably different. Therefore, the presence of the aforementioned short-term periodicities during the last cycle and absence of them in the current cycle may, in principle, be real temporal behavior of the solar rotation during these cycles.