Solar flows and their effect on frequencies of acoustic modes

TL;DR

This study uses quasi-degenerate perturbation theory to analyze how large-scale solar flows affect helioseismic frequencies, finding that some flows are difficult to detect while others may be observable if sufficiently strong.

Contribution

It provides a detailed theoretical analysis of the impact of various large-scale solar flows on helioseismic mode frequencies, offering methods to estimate flow velocities from observational data.

Findings

Meridional circulation effects are below detection thresholds.

Convective flows may be detectable if their amplitudes are large enough.

Limits on flow velocities in giant cells are established.

Abstract

We have calculated the effects of large scale solar flows like the meridional circulation, giant convection cells and solar rotation on the helioseismic splitting coefficients using quasi-degenerate perturbation theory (QDPT). Our investigation reveals that the effect of poloidal flows like the large scale meridional circulation are difficult to detect in observational data of the global acoustic modes since the frequency shifts are much less than the errors. However, signatures of large scale convective flows may be detected if their amplitude is sufficiently large by looking for frequency shifts due to nearly degenerate modes coupled by convection. In this comprehensive study, we attempt to put limits on the magnitude of flow velocities in giant cells by comparing the splitting coefficients obtained from the QDPT treatment with observational data.