A simple helioseismic technique to study convection in the Sun

Convection is the mode of heat transport in the outer third of the Sun, transporting thermal flux outwards. Several techniques that make use of wave oscillations on the surface have been employed over the past few decades to infer properties of the interior. We investigate the power spectra of solar convection over a range of spatial and time scales through the technique of normal-mode coupling. This technique is a unique global helioseismology method in that it retains phase information in its measurements, allowing for the study of time-varying, non-axisymmetric features in the Sun. An important effect that complicates the study of convective velocities is the limited viewing of the Sun, leading to power "leakage" - a smearing effect - in the spectral domain, which in turn leads to noise in the measured signals that need to be removed. We have performed synthetic tests to obtain convective spectra from mode-coupling measurements (Mani & Hanasoge, 2020) and have also utilized this technique to obtain convection spectra from data of Helioseismic Magnetic Imager (HMI) and Michelson Doppler Imager (MDI).