Analyzing Supergranular Power Spectra Using Helioseismic Normal-mode Coupling

Normal-mode coupling is a technique applied to probe the solar interior using surface observations of oscillations. The technique, which is straightforward to implement, makes more use of the seismic information in the wave field than other comparable local imaging techniques and therefore has the potential to significantly improve current capabilities. Here, we examine supergranulation power spectra using mode-coupling analyses of intermediate-to-high-degree modes by invoking a Cartesian-geometric description of wave propagation under the assumption that the localized patches are much smaller in size than the solar radius. We extract the supergranular power spectrum and compare the results with prior helioseismic studies. Measurements of the dispersion relation and lifetimes of supergranulation, obtained using near surface modes (f and p 1), are in accord with the literature. We show that the cross-coupling between the p 2 and p 3 acoustic modes, which are capable of probing greater depths, are also sensitive to supergranulation.