Effect of Magnetic Field Strength on Solar Differential Rotation and Meridional Circulation

TL;DR

This study investigates how magnetic field strength influences solar surface flows, revealing that stronger magnetic elements rotate faster but have slower poleward movement, providing insights into the Sun's internal dynamics.

Contribution

It introduces a magnetic element tracking technique to analyze the dependence of surface flow velocities on magnetic field strength, offering new observational insights.

Findings

Stronger magnetic elements rotate faster than weaker ones.

Magnetic elements with stronger fields have slower meridional circulation.

Results are consistent with previous helioseismic and Doppler measurements.

Abstract

We studied the solar surface flows (differential rotation and meridional circulation) using a magnetic element feature tracking technique by which the surface velocity is obtained using magnetic field data. We used the line-of-sight magnetograms obtained by the Helioseismic and Magnetic Imager aboard the Solar Dynamics Observatory from 01 May 2010 to 16 August 2017 (Carrington rotations 2096 to 2193) and tracked the magnetic element features every hour. Using our method, we estimated the differential rotation velocity profile. We found rotation velocities of $\sim$ 30 and -170 m s$^{-1}$ at latitudes of 0$^{\circ}$ and 60$^{\circ}$ in the Carrington rotation frame, respectively. Our results are consistent with previous results obtained by other methods, such as direct Doppler, time-distance helioseismology, or cross correlation analyses. We also estimated the meridional circulation velocity profile and found that it peaked at $\sim$12 m s$^{-1}$ at a latitude of 45$^{\circ}$, which is also consistent with previous results. The dependence of the surface flow velocity on the magnetic field strength was also studied. In our analysis, the magnetic elements having stronger and weaker magnetic fields largely represent the characteristics of the active region remnants and solar magnetic networks, respectively. We found that magnetic elements having a strong (weak) magnetic field show faster (slower) rotation speed. On the other hand, magnetic elements having a strong (weak) magnetic field show slower (faster) meridional circulation velocity. These results might be related to the Sun's internal dynamics.