Measuring Solar Internal Rotation using Helioseismic Normal-Mode Coupling

Solar internal rotation is intimately linked to the processes that drive and sustain the solar activity cycle. Helioseismology uses the properties of resonant acoustic modes to infer perturbations to the Standard Solar Model, such as flows and structural asphericity. The measurement of rotation as a function of radius and latitude has been one of the most well-established inferences from helioseismology. This measurement invokes the isolated-multiplet approximation. We independently measure solar rotation using normal-mode coupling, which respects cross-coupling of modes across multiplets. Consequently, we also show that the isolated-multiplet approximation breaks down for modes which propagate close to the surface. Can this result in new inferences for solar rotation close to the surface?