The Sun’s near surface shear layer (NSSL) is characterized by using HMI ring-diagram results. It is found the NSSL is composed of three distinct layers: a deeper larger region with a small shear, a narrow middle layer with a strong shear, and a layer very close to the surface.
Quasi-biennial oscillations are found in the Sun’s interior rotation-rate residuals. They appear differently at different depths and latitudes, and evolve with time.
A time variable center-to-limb effect in photospheric velocity measurements through local correlation tracking is identified, and a robust methodology to correct for it is developed.
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 study the physical processes causing the hemispheric sign preference (HSP) of helicity in the Sun, the authors surveyed active regions (ARs) observed during Solar Cycle 24 to estimate their magnetic helicity flux, and studied the HSP dependences of the magnetic helicity flux with respect to various properties of ARs.
Recent discoveries suggest that Sun-like stars experience a fundamental shift in their rotation and magnetism around middle-age. We have now identified this transition in the best available data on stellar cycles.
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.