The sun's magnetic sector structure

The synoptic appearance of solar magnetic sectors is studied using 454 sector boundaries observed at earth from 1959 to 1973. The sectors are clearly visible in the photospheric magnetic field. Sector boundaries can be clearly identified as north-south demarcation lines between regions of persistent magnetic-polarity imbalances. These regions extend up to about 35 deg in latitude on both sides of the equator. They generally do not extend into the polar caps. The polar-cap boundary can be identified as an east-west demarcation line marking the poleward limit of the sectors. The typical flux imbalance for a magnetic sector is about 4 by 10 to the 21st power Mx.