Solar Rotation Rate During the Cycle 24 Minimum in Activity

TL;DR

This study compares the solar rotation rates and zonal-flow patterns during the minima of solar cycles 23 and 24, revealing significant differences and insights into solar dynamics and cycle duration.

Contribution

It provides new insights into the differences in solar rotation and zonal flows between cycle 23 and 24 minima using helioseismic data.

Findings

Significant differences in rotation rates between the two minima.

Bifurcation and recombination of the fast rotating equatorial band.

Cycle 23 lasted approximately 11.7 years based on zonal-flow autocorrelation.

Abstract

The minimum of solar cycle 24 is significantly different from most other minima in terms of its duration as well as its abnormally low levels of activity. Using available helioseismic data that cover epochs from the minimum of cycle 23 to now, we study the differences in the nature of the solar rotation between the minima of cycles 23 and 24. We find that there are significant differences between the rotation rates during the two minima. There are differences in the zonal-flow pattern too. We find that the band of fast rotating region close to the equator bifurcated around 2005 and recombined by 2008. This behavior is different from that during the cycle 23 minimum. By auto-correlating the zonal-flow pattern with a time shift, we find that in terms of solar dynamics, solar cycle 23 lasted for a period of 11.7 years, consistent with the result of Howe et al. (2009). The autocorrelation coefficient also confirms that the zonal-flow pattern penetrates through the convection zone.