Meridional Movements of Individual Sunspots and Pores

TL;DR

This study analyzes the meridional movement of over 360,000 sunspots and pores from 2010 to 2025, revealing how their velocities depend on magnetic polarity, latitude, and development stage, with implications for solar dynamics.

Contribution

It provides new empirical relationships for the meridional velocities of sunspots and pores based on extensive observational data, considering polarity and stage of development.

Findings

Trailing polarity spots move poleward on average.

Velocity depends on latitude with linear and non-monotonic relations.

Maximum meridional speed occurs during sunspot growth phase.

Abstract

The analysis of the meridional displacement velocity of individual solar pores and sunspots has been performed. In the period May 2010\,-\,March 2025 of observations in the continuum of the \textit{Solar Dynamics Observatory/Helioseismic and Magnetic Imager} (SDO/HMI), we identified more than $3.6\cdot 10^{5}$ sunspots and pores for analysis and tracked their displacement. The velocity of the meridional displacement of spots $v_{\rm m}$ depends on their magnetic polarity, latitude, and stage of development. For sunspots and pores of trailing polarity, the velocity of movement is on average directed toward the poles. For such spots, the dependence of the velocity on latitude can be represented by linear regressions for pores: $v^{\rm pr}_{\rm tr} \approx 2.0+0.62\cdot \theta^{\rm o}$ m s$^{-1}$; for sunspots: $v^{\rm sp}_{\rm tr}\approx 0.02+0.94\cdot \theta ^{\rm o}$ m s$^{-1}$. For sunspots and pores of leading polarity, the dependence is non-monotonic in nature on latitude. For pores: $v^{\rm pr}_{\rm ld}\approx 0.35-11.7\cdot {\rm sin}(\theta)+16.5\cdot {\rm sin}^{\rm 2} (\theta) +76.5\cdot {\rm sin}^3 (\theta)-32.7\cdot {\rm sin}^{4}(\theta )$ m s$^{-1}$; for sunspots: $v^{\rm sp}_{\rm ld}\approx -0.35-18.3\cdot {\rm sin}(\theta)+32.2\cdot {\rm sin}^{\rm 2}(\theta) +71.4\cdot {\rm sin}^{\rm 3} (\theta)-6.7\cdot {\rm sin}^{\rm 4}(\theta)$ m s$^{-1}$. The highest speed of meridional movement to the poles is observed for sunspots of trailing polarity during the phase of growth of the sunspot area. The velocity of the meridional movement depends on their area, reaching a maximum for an area of $S\approx 80 - 100$ $\mu$sh.