Long-term variation of the solar polar magnetic fields at different latitudes

TL;DR

This study analyzes the long-term variation of solar polar magnetic fields at different latitudes using Hinode data, revealing non-simultaneous polarity reversals and poleward flux migration.

Contribution

It provides detailed insights into the latitude-dependent polarity reversal process of solar polar magnetic fields based on high-resolution observations.

Findings

Polarity reversals are non-simultaneous in north and south polar caps.

Reversal completes successively from 70° latitude to the pole.

Magnetic flux migrates poleward during reversal process.

Abstract

The polar magnetic fields of the Sun play an important role in governing solar activity and powering fast solar wind. However, because our view of the Sun is limited in the ecliptic plane, the polar regions remain largely uncharted. Using the high spatial resolution and polarimetric precision vector magnetograms observed by Hinode from 2012 to 2021, we investigate the long-term variation of the magnetic fields in polar caps at different latitudes. The Hinode magnetic measurements show that the polarity reversal processes in the north and south polar caps are non-simultaneous. The variation of the averaged radial magnetic flux density reveals that, in each polar cap, the polarity reversal is completed successively from the 70 degree latitude to the pole, reflecting a poleward magnetic flux migration therein. These results clarify the polar magnetic polarity reversal process at different latitudes.