Poleward migration of the magnetic neutral line and the reversal of the polar fields on the sun. II - Period 1904-1940

Abstract

Poleward migration of the magnetic neutral line on the sun has been computed for the period 1904-1940 using synoptic charts based on H-alpha observations and the epochs of sign reversal of the solar magnetic field at latitudes 50 to 90 deg have been determined for this period. During the cycles 16 and 14, a threefold sign reversal took place in the northern and southern hemispheres, respectively. During all the cycles studied both the solar poles were of one polarity for a period ranging from 0.6 to 1.6 years. The poleward drift velocity of the neutral line varies from 4.2 to 8.2 m/s. The apparent relation between the velocity of the filament bands when three bands are present with the bursts of solar activity is discussed.