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Many sunspot cycles are double peaked. In 1967 Gnevyshev suggested thatactually all cycles have two peaks generated by different physical mechanisms,but sometimes the gap between them is too short for the maxima to bedistinguished in indices of the total sunspot activity. Here we show thatindeed all cycles have two peaks easily identified in sunspot activity indifferent latitudinal bands. We study the double peaks in the last 12 sunspotcycles and show that they are manifestation of the two surges of toroidal field- the one generated from the poloidal field advected all the way on the surfaceto the poles, down to the tachocline and equatorward to sunspot latitudes, andanother one generated from the poloidal field diffused at midlatitudes from thesurface to the tachocline and transformed there into toroidal field. Theexistence of these two surges of toroidal field is due to the relativemagnitudes of the speed of the large-scale solar meridional circulation and thediffusivity in the solar convection zone which are estimated from geomagneticdata.

Why the sunspot cycle is double peaked