Transport Velocities in the Convection Zone of the Sun Are Anomalously Weak

Understanding the dynamo action in the Sun, the process by which its magnetic fields are created and sustained, remains a major challenge. Our current understanding of interior convective turbulence, thought to play a critical role in regulating the dynamo, is derived solely from phenomenology and simulation, neither of which addresses the appropriate parameter regime. Here, we seismically constrain transport velocity magnitudes as a function of spherical-harmonic degree $\ell$ and depth in the convection zone to be 20 - 100 times lower than predictions from the current simulation methodologies and mixing length models. These bounds are obtained by isolating waves that propagate to specific depths and searching for statistical evidence for deviations in their travel times due to advection by convective flows. Turbulence on scales $\ell \le 60$ persists in a strongly rotationally-dominated regime of {\it geostrophy} since the Rossby numbers at $r/R_\odot = 0.96$, where $R_\odot$ is the solar radius, are less than $\sim 10^{-2}$.