Several topics concerning the subsurface structure and evolution of sunspots are discussed. These include the morphology and stability of the magnetized plasma below a sunspot as well as the heat blockage in it. Current ideas on the origin and physical processes preceding the formation of an active region are reviewed.

Several topics concerning the subsurface structure and evolution of sunspots are discussed. These include the morphology and stability of the magnetized plasma below a sunspot as well as the heat blockage in it. In the second part of this paper, current ideas on the origin and physical processes preceding the formation of an active region are

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The radial velocity limb shift effect has been measured for the K I 7699 Å line using a resonant scattering spectrophotometer in the summer of 1982. On the other hand, using integral sunlight, the line of sight velocity has been measured during the years 1976 to 1986 and the gravitational redshift determined. This value shows a variation over those

The intensity distribution of the penumbra at different stages of evolution has been analyzed. The results have been different for both evolved and primitive penumbras. While the former present almost symmetrical, single-peaked histograms, the same does not occur for the latter, their distributions being, preferentially, asymmetrical or double