Polarity imbalance of the photospheric magnetic field

TL;DR

This study analyzes the 22-year periodicity of polarity imbalance in the Sun's photospheric magnetic field across different latitudes and field strengths, revealing its connection to the Sun's global magnetic properties and interplanetary magnetic field structure.

Contribution

It provides new insights into the polarity imbalance patterns over four solar cycles and their relation to the Sun's global magnetic field and sector structure.

Findings

22-year periodicity in polarity imbalance observed

Imbalance sign correlates with hemisphere polarity and magnetic field asymmetry

Weak magnetic fields develop in antiphase with stronger fields

Abstract

Polarity imbalance of the photospheric magnetic field was studied using synoptic maps of NSO Kitt Peak (1976-2016). Imbalance of positive and negative fluxes was considered for the fields with strength B>50 G in the sunspot zone (5 deg - 40 deg) and for the fields with strength B<50 G at higher latitudes (40 deg - 90 deg). The 22-year periodicity in the imbalance of positive and negative fields was found which maintained itself during four solar cycles. While for the sunspot zone the sign of the imbalance always coincides with the northern hemisphere polarity, for the high latitudes the sign of the imbalance always coincides with the southern hemisphere polarity. Good correspondence of the flux imbalance with the quadrupole moment (g20) of the potential-field source-surface (PFSS) model was observed. The polarity imbalance of the sunspot zone correlates, on one hand, with the asymmetry of the magnetic field of the Sun-as-a-star and, on the other hand, with the sector structure of the interplanetary magnetic field. The obtained results show the close connection of the magnetic fields in active regions with the Sun's polar magnetic field. The weakest fields B<5 G represent quite a special group with the magnetic flux developing in antiphase to the fluxes of the stronger fields.