Imaging the Sun's near-surface flows using mode-coupling analysis

Abstract

The technique of normal-mode coupling is a powerful tool with which to seismically image nonaxisymmetric phenomena in the Sun. Here we apply mode coupling in the Cartesian approximation to probe steady, near-surface flows in the Sun. Using Doppler cubes obtained from the Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory, we perform inversions on mode-coupling measurements to show that the resulting divergence and radial vorticity maps at supergranular length scales (∼30 Mm) near the surface compare extremely well with those obtained using the Local Correlation Tracking method. We find that the Pearson correlation coefficient is ≥ 0.9 for divergence flows, while ≥ 0.8 is obtained for the radial vorticity.