Bright rings around sunspots

There are two possible explanations for why sunspots are dark: the partial suppression by the sunspot magnetic fields of convective energy transport f rom the underlying layers', or the removal of energy from the sunspot by en hanced hydromagnetic wave radiation(2). Both processes would reduce the ene rgy emitted radiatively, The first explanation is currently favoured(3), an d predicts that the blocked energy should show up as a bright ring around t he spot(2), with the actual brightness of the ring sensitive to details of solar convective transport and sunspot structure(4), Previous searches(5) f or these bright rings were inconclusive because of the presence of bright, vertical magnetic nux tubes near the spots, and a lack of sufficient precis ion in the observations. Here we report high-photometric-precision observat ions of bright rings around eight sunspots. The rings are about 10 K warmer than the surrounding photosphere and extend at least one sunspot radius ou t from the penumbra, About 10% of the radiative energy missing from the sun spots is emitted through the bright rings. We also report observations of a second set of sunspots, for which simultaneous magnetic field measurements demonstrate that the rings are not associated with vertical nux tubes.