On the initial orientation of emerging active regions

The initial orientation of 74 active regions is measured in high resolution pictures. As previous works by the author (García de la Rosa, 1984) suggest a different behaviour between large and small active regions, the sample has been divided into those two classes, whose dividing line is roughly set at 5 × 10²¹ Mx in the magnetic flux. It is observed that only the large regions tend to display the correct inclination (p-part at lower latitude). Their evolution towards a more parallel inclination to the equator is also observed. The first finding is interpreted in terms of the primary nature of the large ARs which are supposed to be directly linked to the basic mechanism of solar activity. The evolution is interpreted as a reaction of the lower layers of the tube to the tilt introduced by the Coriolis effect.