A new method to derive the helioseismic sensitivity kernels for the Sun’s large-scale internal flows is developed. The new method is based on the idea of placing a small-volume flow perturbation inside the Sun’s model, simulating the wavefield in the photosphere, and then measuring the phase shifts caused by this internal perturbation.
Newly developed time-distance helioseismic imaging method, which includes more multiskip acoustic waves, is proved to be more reliable in mapping the Sun’s far-side active regions.
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.
Meridional flows during the solar minimum and maximum years are derived using 14 years of SOHO/MDI data. The flows changed significantly from the minimum to the maximum, and major changes were associated with the active latitudes.
The systematic Center-to-Limb effect in time-distance helioseismic measurements is found to be significantly frequency dependent. The dependence further varies with disk-centric distance but not with travel distance.
A more comprehensive time-distance helioseismic method is developed to derive the Sun’s meridional circulation, and a 3-layer flow structure is found through the convection zone.
A newly discovered, fast-moving wave propagates outward along sunspots’ radial direction and may provide new diagnostics of the sunspot subsurface structure.
What could be common between solar atmosphere and information exchange in communicating systems? Well, this is all about how information is transferred from point A to point B. This work represents a proof-of-concept application of methods of mutual information (MI) to helioseismology.
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.