An analysis of the center to limb variation of the geometrical properties of spots has been carried out. It has revealed that spots do not have a symmetrical behaviour with respect to the centre of solar disk. Thus, the Wilson effect is not zero at δ = 0°, but at δ ≡ 45°W. Moreover, the inverse Wilson effect is the general rule in that interval

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