Injection of magnetic helicity in solar cycle 24 and early phase of cycle 25

TL;DR

This study quantifies magnetic helicity injection during solar cycles 24 and 25, highlighting active regions as primary contributors and linking helicity fluctuations to complex subsurface processes.

Contribution

It provides the first detailed analysis of magnetic helicity injection across two solar cycles using synoptic magnetic charts, emphasizing the role of active regions and magnetic polarity reversals.

Findings

Magnetic helicity injection is mainly from active regions.

Polarities of active regions reverse between cycles 24 and 25.

Fluctuations in helicity reflect complex subsurface magnetic processes.

Abstract

The injection of magnetic helicity into the heliosphere during solar cycle 24 and the early phase of cycle 25 has been calculated based on the analysis of a series of synoptic magnetic charts. During the cycle, the injected magnetic helicity is found to be mainly contributed by the magnetic field in active regions. According to Hale's law, the polarities of active regions statistically reverse between solar cycles 24 and 25. We suggest that the dominant source of injected magnetic helicity likely arises from the relatively strong magnetic fields of the leading polarity of active regions. This occurs as part of the magnetic field that migrates to high latitudes and the polar regions of the Sun due to the effect of meridional circulation inferred from a series of HMI/SDO magnetic synoptic charts. Significant fluctuations of the injected magnetic helicity from the subsurface layers may reflect the complex processes of how the twist from the convection zone ejects magnetic fields through a series of active regions on different temporal and spatial scales at the solar surface.