Inferring Quadrupolar Dynamo Mode from Sunspot Statistics

TL;DR

This paper introduces a method to infer the quadrupolar component of the solar dynamo by analyzing sunspot data, revealing oscillations that indicate the presence of this mode alongside the dominant dipolar mode.

Contribution

It proposes a novel approach using sunspot area as a proxy for subsurface magnetic flux to detect quadrupolar oscillations in the solar dynamo.

Findings

Detection of 16-year quadrupolar oscillations in sunspot data.

Identification of the quadrupolar mode amplitude as about 0.17 relative to the dipolar mode.

Evidence supporting the coexistence of dipolar and quadrupolar modes in solar magnetic activity.

Abstract

Observations of long-term north-south asymmetry in solar activity demand the equator-symmetric (quadrupolar) mode be present in the solar magnetic field in line with the dominant antisymmetric (dipolar) mode. This paper proposes treating the sunspot area as a proxy for subsurface toroidal magnetic flux to infer the quadrupolar mode of the solar dynamo from sunspot data. Toroidal pseudo-fluxes (PF) in the northern and southern hemispheres are defined as a signed sunspot area with plus or minus sign prescribed to them in accord with the Hale's sunspot polarity rules. Statistical correlation analysis and wavelet analysis of so-defined PFs reveal quadrupolar oscillations with a period of about 16 yr and amplitude of about 0.17 relative to the amplitude of the dominant 22-yr dipolar mode.