Using 15+ years of HMI ring-diagram data, the authors measure near-surface solar rotation and introduce cumulative longitudinal displacement, a new diagnostic revealing torsional oscillations, hemispheric asymmetries, and possible links to high-latitude magnetic flux transport.
Oscillatory phase shifts were measured between Doppler velocities observed by GONG and HMI at the same locations on the solar disk over a 14-year period. The two datasets exhibit disk-position-dependent phase differences, indicating the presence of phase anomalies that may introduce systematic errors into inferences of the Sun’s meridional circulation and internal rotation.
Using 14 years of helioseismic and magnetic-field observations, this study shows that deeper subsurface outflows from active regions play an important role in transporting magnetic fluxes to the polar regions and regulating polar-field formation.
Spatiotemporal images of solar magnetic fluxes, made using the near-side magnetic-field observations and helioseismic far-side images, are analyzed separately using flux integration and power-spectrum analysis. Both results are consistent and imply that the surface active regions’ clustering patterns are likely imprints of magneto-Rossby waves in the tachocline.
Helioseismic analysis of solar torsional oscillations reveals dynamo-wave–like signatures that originate near the tachocline and propagate through the convection zone, linking internal zonal flows to the surface magnetic cycle. Additional evidence from frequency-splitting coefficients and rotational shear variations shows strong solar-cycle correlations, supporting the tachocline as a primary site of solar dynamo action.
Equatorial Rossby waves at different depths are studied, and it is found that the Rossby waves are tilted retrograde with depth rather than being a columnar structure. The tilt remains relatively stable through the solar cycle without being consistently modulated by magnetic activity.
High-latitude m=1 inertial modes were analyzed and characterized using the time-distance helioseismic subsurface flows. It was found that the mode’s power exhibits an anti-correlation with solar activity. Magnetic flux transported from low to high latitudes influences both the mode’s power and lifetime, enhancing its power and shortening its lifetime upon arrival.
Strong acoustic scatterers are found beneath sunspot umbrae and penumbrae using the phase-correlation holography method. These scatterers indicate the fragmentation of magnetic flux, as suggested by Eugene Parker in the 1970s.
Is the solar meridional circulation profile single-, double-, or multiple-cell? At least, a constraint of equatorward angular momentum transport by meridional circulation favors the double-cell structure, although the inversion with a constraint of mass conservation favors single cell.
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.