AXIAL TILT ANGLES OF ACTIVE REGIONS

Separate Mount Wilson plage and sunspot group data sets are analyzed i n this review to illustrate several interesting aspects of active regi on axial tilt angles. (1) The distribution of tilt angles differs betw een plages and sunspot groups in the sense that plages have slightly h igher tilt angles, on average, than do spot groups. (2) The distributi ons of average plage total magnetic Bur, or sunspot group area, with t ilt angle show a consistent effect:: those groups with tilt angles nea rest the average values are larger (or have a greater total flux) on a verage than those farther from the average values. Moreover, the avera ge tilt angles on which these size or flux distributions are centered differ for the two types of objects, and represent closely the actual different average tilt angles for these two features. (3) The polarity separation distances of plages and sunspot groups show a clear relati onship to average tilt angles. In the case of each feature, smaller po larity separations are correlated with smaller tilt angles. (4) The dy namics of regions also show a clear relationship with region tilt angl es. The spot groups with tilt angles nearest the average value (or per haps 0-deg tilt angle) have on average a faster rotation rate than tho se groups with extreme tilt angles. All of these tilt-angle characteri stics may be assumed to be related to the physical forces that affect the magnetic flux loop that forms the region. These aspects are discus sed in this brief review within the context of our current view of the formation of active region magnetic flux at the solar surface.