Differential Rotation of Individual Sunspots and Pores

TL;DR

This study analyzes the rotation rates of over 210,000 individual sunspots and pores using SDO/HMI data from 2010 to 2024, revealing differences based on polarity, structure, and size, and their relation to solar atmospheric rotation.

Contribution

It provides a detailed analysis of the differential rotation of sunspots and pores, highlighting how their rotation rates depend on polarity, structure, and size, using extensive observational data.

Findings

Leading polarity spots rotate faster than trailing polarity spots.

Sunspots with umbra and penumbra rotate faster than pores without penumbra.

Small sunspots rotate slower than larger ones, with a threshold at 10 μhm.

Abstract

The analysis of the rotation rate of individual sunspots and pores was performed according to the data of the processing of observations by the \textit{Solar Dynamics Observatory/Helioseismic and Magnetic Imager} (SDO/HMI) in the period 2010\,--\,2024. Sunspots stood out in the images in the continuum. To accurately track the spots, we processed 5 images for each day. To determine the polarity of the magnetic field, we superimposed the contours of sunspots on observations of magnetic fields at the same time. This made it possible to track the movement of more than 210 thousand individual sunspots and pores. It is found that the rotation rate is influenced by the rotation rate of the solar atmosphere and the systematic proper motions of the spots. Sunspots and pores of the leading polarity have a rate of meridional movement $\approx 2.4\%$ faster than spots of the trailing polarity. We also found that regular sunspots, which have umbra and penumbra, rotate $\approx 1.5\%$ faster than solar pores, in which penumbra is absent. The dependence of the rotation rate on these area is found. For sunspots with an area of $S> 10$ $\mu$hm, the rotation rate is practically independent of these area. Small sunspots, with an area of lower than $S< 10$ $\mu$hm, rotate $\approx 1.7\%$ slower.