Testing Helioseismic-Holography Inversions for Supergranular Flows Using Synthetic Data

TL;DR

This study evaluates the accuracy of helioseismic holography inversions for supergranular flows using synthetic data from the SPARC code, highlighting strengths and limitations in current measurement techniques.

Contribution

It demonstrates the effectiveness and limitations of RLS inversions in reproducing supergranular flow structures from synthetic helioseismic data.

Findings

RLS inversions successfully reproduce horizontal flow structures.

Significant errors occur near domain boundaries and in vertical flows.

Vertical velocity errors are mainly due to cross talk from horizontal flows.

Abstract

Supergranulation is one of the most visible length scales of solar convection and has been studied extensively by local helioseismology. We use synthetic data computed with the Seismic Propagation through Active Regions and Convection (SPARC) code to test regularized-least squares (RLS) inversions of helioseismic holography measurements for a supergranulation-like flow. The code simulates the acoustic wavefield by solving the linearized three-dimensional Euler equations in Cartesian geometry. We model a single supergranulation cell with a simple, axisymmetric, mass-conserving flow. The use of simulated data provides an opportunity for direct evaluation of the accuracy of measurement and inversion techniques. The RLS technique applied to helioseismic-holography measurements is generally successful in reproducing the structure of the horizontal flow field of the model supergranule cell. The errors are significant in horizontal-flow inversions near the top and bottom of the computational domain as well as in vertical-flow inversions throughout the domain. We show that the errors in the vertical velocity are due largely to cross talk from the horizontal velocity.