Dots inside a sunspot!
Swedish 1m Solar Telescope
Umbral dots are a signature that convection is happening even inside a sunspot. In principle, the enormous magnetic fields that form a sunspot inhibit the normal convection on the solar surface. But still some smaller signs of convection can be observed in the umbra and penumbra of sunspots in the form of umbral dots and light bridges. These observations show, in very high spatial resolution, the presence of those umbral dots (bright) embedded in the dark umbra and were taken with the Crisp Imaging Spectropolarimeter at the Swedish 1-m Solar Telescope in the neutral iron line at 6302 A. The figure shows from top to bottom: continuum intensity images, velocity maps derived from the spectral profiles, and maps of the net circular polarisation which reveal gradients of the magnetic field and/or the velocity along the line of sight. The temporal evolution of these features is studied by recording images at different consecutive times.
Umbral dots harbor upflows in the center and downflows at the edges, which is a typical sign of magnetoconvection, that is, convection in the presence of magnetic fields.
Image credit: Ada Ortiz, Luc Rouppe van der Voort (ITA, University of Oslo)
Publication: Ortiz et al., 2010, ApJ, 713, 1282