The Solar spots - are the dark formations on the Sun's disk. ... The greatest observed spot is 100 thousand kilomiters. The spots are the places of the magnetic fields' getting out to the solar atmosphere. ... That's why they look so dark . ... The Solar convection zone is the layer with the thickness of 150 - 200 thousand kilomiters, situated under the photosphere; the substance of this layer being in convectional movement transformes the energy from inside the Sun's to its surface. ...