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The Sun's internal rotation {\Omega}(r,{\Theta}) has previously been measuredusing helioseismology techniques and found to be a complex function ofco-latitude, {\theta}, and radius, r. From helioseismology and observations ofapparently "rooted" solar magnetic tracers we know that the surface rotatesmore slowly than much of the interior. The cause of this slow-down is notunderstood but it is important for understanding stellar rotation generally andany plausible theory of the solar interior. A new analysis using 5-min solarp-mode limb oscillations as a rotation "tracer" finds an even larger velocitygradient in a thin region at the top of the photosphere. This shear occurswhere the solar atmosphere radiates energy and angular momentum. We suggestthat the net effect of the photospheric angular momentum loss is similar toPoynting-Robertson "photon braking" on, for example, Sun-orbiting dust. Theresultant photospheric torque is readily computed and, over the Sun's lifetime,is found to be comparable to the apparent angular momentum deficit in thenear-surface shear layer.

A Poynting-Robertson-like drag at the Sun's surface