Single spots, unipolar magnetic regions, and pairs of spots: 2. the development of sunspot pairs and the Hale boundary

Abstract

Sunspot pairs develop in connection with cell networks at or near the boundaries of positive and negative unipolar magnetic (UM) field regions. In this paper, we confirm his findings by recent data. In this connection, Svalgaard and Wilcox (1976) found also that solar activities occur only at one side of UM boundaries, called the "Hale boundary," on the basis of their observation of the interplanetary magnetic field. It is shown in this paper that the Hale boundary can be recognized also on the photosphere. Further, it is shown that new UM regions grow at the beginning of a new sunspot cycle, and active regions and sunspot pairs tend to develop at or near newly developing Hale boundaries. Thus, it is suggested that UM regions and specifically Hale boundaries are very important for the formation of active regions, sunspots, and sunspot pairs. These facts suggest also that UM regions are not merely remnants of decaying old spots and active regions. Some of the essential features of sunspot pairs, as well as their relationship to the Hale boundary in both even and odd cycles are presented in one figure, illustrating several requirements for a theory of the formation of single spots and sunspot pairs.