  Convection is the mechanism by which energy is transported through the
outermost 30% of the Sun. Solar turbulent convection is notoriously difficult
to model across the entire convection zone where the density spans many orders
of magnitude. In this issue of PNAS, Hanasoge et al. (2012) employ recent
helioseismic observations to derive stringent empirical constraints on the
amplitude of large-scale convective velocities in the solar interior. They
report an upper limit that is far smaller than predicted by a popular
hydrodynamic numerical simulation.
