Deep-Focus Diagnostics of Sunspot Structure

TL;DR

This paper uses numerical models and helioseismology to investigate the structure of sunspots, focusing on wave-speed perturbations and testing the applicability of MHD ray theory for future diagnostics.

Contribution

It extends previous surface-focused helioseismic measurements with a deep-focusing scheme and compares MHD forward models to evaluate their effectiveness for sunspot diagnostics.

Findings

Deep-focusing travel-time measurements are effective in probing sunspot structure.

MHD ray theory shows promise for future sunspot inverse modeling.

Comparison of models enhances understanding of wave-speed perturbations.

Abstract

In sequel to Moradi et al. [2009, ApJ, 690, L72], we employ two established numerical forward models (a 3D ideal MHD solver and MHD ray theory) in conjunction with time-distance helioseismology to probe the lateral extent of wave-speed perturbations produced in regions of strong, near-surface magnetic fields. We continue our comparisons of forward modeling approaches by extending our previous surface-focused travel-time measurements with a common midpoint deep-focusing scheme that avoids the use of oscillation signals within the sunspot region. The idea is to also test MHD ray theory for possible application in future inverse methods.