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.
Multi-height Doppler velocity maps from two layers separated by 50 km are obtained from combinations of currently recorded HMI filtergrams. Using synthetic data of spectral line profiles produced in a convective environment, we test the ability to recover vertical velocity fields at different heights.
Numerical simulations of solar rotation and dynamo have been performed over the last decades with the aim of understanding the physics of the solar interior. Here we briefly discuss two main approaches, namely, mean-field modeling and global simulations. We also present recent results of hydrodynamic global simulations which reveal interesting aspects of stellar rotation.
The magnetic field of active region NOAA 11092 shows a persistent counter-clockwise twist in the solar atmosphere from the photosphere to the corona. The subsurface flows associated with this region are twisted in the opposite direction.
New solar fluorine abundance was determined using improved molecular data. The new abundance is slightly lower than the old values previously determined in 1960s.
Subsurface meridional flow speed shows an anti-correlation with the magnetic flux being transported poleward above the latitude of 35°. In the lower latitude, the residual meridional flow, after a long-time mean profile is subtracted, shows converging flow toward the activity belts.
Motivated by recent observations we have explored whether the flux-transport dynamo model can work with multi-cell meridional flow. We find that it can work when certain conditions are fulfilled.
Giant convection cells discovered with HMI Doppler data are found to transport angular momentum equatorward. This helps to resolve the 400-year old mystery of the Sun’s rapidly rotating equator.
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.
Solar meridional circulation, if mechanically driven and thermally
braked, contains two cells in latitude; generating two cells in depth,
recently observed by SDO/HMI, is a new challenge to theory.