On the Rotation of Sunspots and Their Magnetic Polarity

TL;DR

This study analyzes the rotation and magnetic polarity of sunspots over two solar cycles, revealing hemispheric and temporal patterns in their rotational directions and magnetic polarities.

Contribution

It provides new observational insights into the relationship between sunspot rotation, magnetic polarity, and hemispheric differences across solar cycles.

Findings

Sunspots in 2003 tended to rotate counterclockwise with positive polarity in the north.

In 2014/2015, sunspots rotated clockwise with negative polarity in the north.

Opposite rotation directions were observed for sunspots in the same hemisphere between the two periods.

Abstract

The rotation of sunspots of 2 yr in two different solar cycles is studied with the data from the Helioseismic and Magnetic Imager on board the \it Solar Dynamics Observatory \rm and the Michelson Doppler Imager instrument on board the \it Solar and Heliospheric Observataory.\rm We choose the $\alpha$ sunspot groups and the relatively large and stable sunspots of complex active regions in our sample. In the year of 2003, the $\alpha$ sunspot groups and the preceding sunspots tend to rotate counterclockwise and have positive magnetic polarity in the northern hemisphere. In the southern hemisphere, the magnetic polarity and rotational tendency of the $\alpha$ sunspot groups and the preceding sunspots are opposite to the northern hemisphere. The average rotational speed of these sunspots in 2003 is about $0^{\circ}.65 \rm \ hr^{-1}$. From 2014 January to 2015 February, the $\alpha$ sunspot groups and the preceding sunspots tend to rotate clockwise and have negative magnetic polarity in the northern hemisphere. The patterns of rotation and magnetic polarity of the southern hemisphere are also opposite to those of the northern hemisphere. The average rotational speed of these sunspots in 2014/2015 is about $1^{\circ}.49 \rm \ hr^{-1}$. The rotation of the relatively large and stable preceding sunspots and that of the $\alpha$ sunspot groups located in the same hemisphere have opposite rotational direction in 2003 and 2014/2015.