We study the m = 1 high-latitude inertial mode and its contribution to the latitudinal transport of the Sun’s angular momentum. Ring-diagram helioseismology applied to 5° tiles is used to obtain the horizontal flows near the surface of the Sun. Using 10 years of data from SDO/HMI, we report on the horizontal eigenfunction and Reynolds stress $\[{Q_{\theta \phi }} = \langle {u'_\theta }{u'_\phi }\rangle \]$ for the m = 1 high-latitude inertial mode (frequency –86.3 nHz, critical latitudes ±58°). We find that Qθφ takes significant values above the critical latitude and is positive (negative) in the northern (southern) hemisphere, implying equatorward transport of angular momentum. The Qθφ peaks above latitude 70° with a value of 38 m2/s2.

We present analysis of the evolution of subsurface flows in and around active regions with peculiar magnetic configurations and compare their characteristics with the normal active regions. We also study the zonal and meridional components of subsurface flows separately in different polarity regions separately to better understand their role in flux migration. We use the techniques of local correlation tracking and ring diagrams for computing surface and subsurface flows, respectively. Our study manifests an evidence that the meridional component of the flows near anti-Hale active regions is predominantly equatorward which disagrees with the poleward flow pattern seen in pro-Hale active regions. We also find clockwise or anti-clockwise flows surrounding the anti-Joy active regions depending on their locations in the Southern or Northern hemispheres, respectively.

We have measured zonal and meridional components of subsurface flows up to a depth of 30 Mm below the solar surface by applying the technique of ring diagram on Dopplergrams which are constructed from the spherical harmonic (SH) coefficients. The SH coefficients are obtained from the Helioseismic and Magnetic Imager (HMI) full-disk Dopplergrams. We find a good agreement and some differences between the flows obtained in this study with those from the traditional methods using direct Dopplergrams.

The Sun’s global inertial modes are very sensitive to the solar differential rotation and to properties of the deep solar convection zone which are currently poorly constrained. These properties include the superadiabatic temperature gradient, the latitudinal entropy gradient, and the turbulent viscosity. The inertial modes also play a key role in controlling the Sun’s large-scale structure and dynamics, in particular the solar differential rotation. This paper summarizes recent observations and advances in the (linear and nonlinear) modeling of the solar inertial modes.

Using the data on sunspot groups compiled during 1879–1975, we determined variations in the differential rotation coefficients A and B during the solar cycle. The variation in the equatorial rotation rate A is found to be significant only in the odd numbered cycles, with an amplitude ∼ 0.01 μ rads −1. There exists a good anticorrelation between the variations of the differential rotation rate B derived from the odd and even numbered cycles, suggesting existence of a ‘22-year’ periodicity in B. The amplitude of the variation of B is ∼ 0.05 μ rads −1.