Solar images observed at a) 17 GHz; b) 304 Å; and c) 171 Å. The concentric circles delimited the analyzed regions and the dashed arcs demarcated the polar regions a), the equatorial southern b) and northern c) hemispheres, respectively. The mean relative intensities (I_R) resulting from the analyses for the three wavelengths are shown in the bottom panels (d), e) and f)). The south and north poles were delimited in the ranges 60−120° and 240−300°, respectively (dotted lines in the panels).