Abstract
The application of local correlation tracking to the proper motions of granules yields the horizontal velocity field at the solar surface. The divergence of the velocity reveals a pattern of sources and sinks. The vorticity is concentrated at sinks to form local swirls (with either sense of motion). A simple kinematic model of such a vortex, in which the radial inflow is balanced by an eddy viscosity, predicts that the vorticity should have a Gaussian profile. This prediction is confirmed by comparison with three sets of high-resolution observations, obtained from Spacelab 2 and from the Swedish Vacuum Solar Telescope on La Palma. Finally, we develop a more precise version of the model and provide an estimate of the eddy viscosity due to small-scale granulation.
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