Twelve years of HMI Dopplergram and magnetogram data have been used to uncover the solar cycle dependence of the magnetically quietest regions on the Sun and to reveal an enigmatic behavior of the surface-gravity wave energy contained in those regions.
The giant cellular flows, obtained through tracking HMI-observed Dopplergrams, are used to estimate kinetic helicity and Reynolds stress inside the Sun, as well as differential rotation and poleward drift near the bottom of the convection zone.
To minimize cross-talk effect from vertical flows and sound-speed perturbations, a new inversion code is developed to invert for flows and sound-speed perturbations simultaneously from time-distance travel-time measurements. The code is validated using numerical simulation data.
The mean size of supergranulation has been found to vary over time with a period of 3-5 days. We have used full-disk Doppler images from the Helioseismic Magnetic Imager (HMI) to verify that these fluctuations are solar in origin.
Flow system in an average supergranule is compared to the moat flow around axisymmetric sunspots. Both phenomena are very similar, only the outflow in the moat is distorted due to the proper motion of the sunspot with respect to the local frame of rest and moat is a purely downflow region.
Observed seismic upper bounds on large-scale lateral (horizontal) convective-velocity amplitudes in the solar interior at the depth r/R = 0.96 do not agree with modeling results derived at a similar depth from global convection simulations. The observations of low convective-velocity amplitudes throw into question our understanding of thermal and angular momentum transport in the Sun.
Analysis of a large number of supergranules observed with HMI and simulations with a convectively stabilized solar model imply that the average supergranular cell has a peak upflow of 240 m s-1 at a depth of 2.3 Mm and a corresponding peak outward horizontal flow of 700 m s-1 at a depth of 1.6 Mm.