Periodicities in the coronal rotation and sunspot numbers

TL;DR

This study analyzes long-term variations in coronal rotation using solar radio emission data from 1947 to 2009, revealing a mean rotation period of 24.3 days and identifying a 22-year cycle linked to the solar magnetic cycle.

Contribution

It provides new insights into the long-term periodicities of coronal rotation and their correlation with sunspot cycles, especially highlighting the 22-year Hale cycle.

Findings

Coronal rotation period varies between 19.0 and 29.5 days.

A 22-year component related to the solar magnetic cycle was identified.

Correlations between sunspot numbers and rotation period align with Hale's cycle.

Abstract

The present study is an attempt to investigate the long term variations in coronal rotation by analyzing the time series of the solar radio emission data at 2.8 GHz frequency for the period 1947 - 2009. Here, daily adjusted radio flux (known as Penticton flux) data are used. The autocorrelation analysis shows that the rotation period varies between 19.0 to 29.5 sidereal days (mean sidereal rotation period is 24.3 days). This variation in the coronal rotation period shows evidence of two components in the variation; (1) 22-years component which may be related to the solar magnetic field reversal cycle or Hale's cycle, and (3) a component which is irregular in nature, but dominates over the other components. The crosscorrelation analysis between the annual average sunspots number and the coronal rotation period also shows evidence of its correlation with the 22-years Hale's cycle. The 22-years component is found to be almost in phase with the corresponding periodicities in the variation of the sunspots number.