Comparison of solar surface flows inferred from time--distance helioseismology and coherent structure tracking using HMI/SDO observations

TL;DR

This study compares two methods of measuring solar surface flows using HMI/SDO data, finding good correlation and agreement with Doppler measurements, enhancing confidence in helioseismic and tracking techniques.

Contribution

It provides a direct comparison and validation of helioseismic and coherent structure tracking methods for solar surface flow measurements.

Findings

Strong correlation between helioseismic and tracking flow measurements

Good agreement with Doppler line-of-sight velocities

Validation of vertical flow estimates from 3D inversions

Abstract

We compare measurements of horizontal flows on the surface of the Sun using helioseismic time--distance inversions and coherent structure tracking of solar granules. Tracking provides 2D horizontal flows on the solar surface, whereas the time--distance inversions estimate the full 3-D velocity flows in the shallow near-surface layers. Both techniques use HMI observations as an input. We find good correlations between the various measurements resulting from the two techniques. Further, we find a good agreement between these measurements and the time-averaged Doppler line-of-sight velocity, and also perform sanity checks on the vertical flow that resulted from the 3-D time--distance inversion.