Magnetic shear. III - Hale region 17255

Hale active region 17255, which in many respects was the most vigorous active region observed during the first operational period of SMM, appears to lie between two large areas of flow (observed in C IV) converging toward the major axis of the region. In the 6-day period from November 6-12, 1980, the major axis of the region rotates by about 25 deg. Several segments of the magnetic neutral line show C IV flow velocities of opposite sign on either side of the neutral line. Those segments whose orientation is favorable for measuring velocity components parallel to the neutral line show evidence that such flow is present, which is interpreted as evidence for magnetic shear. This, together with other evidence, suggests that magnetic shear is widespread in this region, as in the two previous regions studied. It is concluded that magnetic shear is often associated with flaring activity but is not a sufficient condition for flaring to occur.