# Solar Magnetic Field Signatures in Helioseismic Splitting Coefficients

## TL;DR

This study uses helioseismic splitting coefficients to analyze the evolution of solar magnetic fields during cycle 23, revealing a combination of poloidal and toroidal fields with specific strengths and surface activity correlations.

## Contribution

It introduces a method to infer large-scale magnetic field configurations in the solar interior from helioseismic data, highlighting the near-surface magnetic field structures during solar cycle 23.

## Key findings

- Identified a poloidal dipole field with peak strength 124 G.
- Detected two toroidal fields near the surface with strengths up to 1.4 kG.
- Found magnetic field strengths correlate with surface activity and show hysteresis effects.

## Abstract

Normal modes of oscillation of the Sun are useful probes of the solar interior. In this work, we use the even-order splitting coefficients to study the evolution of magnetic fields in the convection zone over solar cycle 23, assuming that the frequency splitting is only due to rotation and a large scale magnetic field. We find that the data are best fit by a combination of a poloidal field and a double-peaked near-surface toroidal field. The toroidal fields are centered at r=0.999R_solar and r=0.996R_solar and are confined to the near-surface layers. The poloidal field is a dipole field. The peak strength of the poloidal field is 124 +/- 17G. The toroidal field peaks at 380 +/- 30G and 1.4 +/- 0.2kG for the shallower and deeper fields respectively. The field strengths are highly correlated with surface activity. The toroidal field strength shows a hysteresis-like effect when compared to the global 10.7 cm radio flux. The poloidal field strength shows evidence of saturation at high activity.