Solar Magnetic Field Reversals and the Role of Dynamo Families

TL;DR

This paper analyzes the solar magnetic field's reversals by decomposing observational data into harmonic modes, exploring their interactions through dynamo theory, and using mean-field models to understand long-term magnetic trends.

Contribution

It introduces a harmonic decomposition approach to study mode interactions and their role in solar magnetic reversals, linking observational data with dynamo theory and mean-field models.

Findings

Mode coupling correlates with polarity reversals.

Harmonic analysis reveals mode interactions over solar cycles.

Mean-field models replicate observed magnetic trends.

Abstract

The variable magnetic field of the solar photosphere exhibits periodic reversals as a result of dynamo activity occurring within the solar interior. We decompose the surface field as observed by both the Wilcox Solar Observatory and the Michelson Doppler Imager into its harmonic constituents, and present the time evolution of the mode coefficients for the past three sunspot cycles. The interplay between the various modes is then interpreted from the perspective of general dynamo theory, where the coupling between the primary and secondary families of modes is found to correlate with large-scale polarity reversals for many examples of cyclic dynamos. Mean-field dynamos based on the solar parameter regime are then used to explore how such couplings may result in the various long-term trends in the surface magnetic field observed to occur in the solar case.