Poleward migration of the magnetic neutral line and the reversal of the polar fields on the sun. I - Period 1945-1981

Abstract

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 H-alpha observations. Epochs of sign reversal of the solar magnetic field at latitudes 50 to 90 deg 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 and seems to depend on the strength of the cycle.