Poleward Migration of the Magnetic Neutral Line and the Reversal of the Polar Fields on the Sun - Part One - Period 1945-1981

Poleward migration of the magnetic neutral line on the Sun has been calculated for the periods 1945-1950 and 1955-1981 using synoptic charts based on Hα observations. Epochs of sign reversal of the solar magnetic field at latitudes 50° to 90° have been determined for these periods. During the cycles 19 and 20 a threefold sign reversal took place in the northern hemisphere. During all the above cycles both the solar poles were of one polarity for a period ranging from 0.5 to 1 year. The poleward drift velocity of the magnetic neutral line varies from 6 to 29 m s⁻¹ and seems to depend on the strength of the cycle.