Magnetic shear. IV - Hale regions 16740, 16815, and 16850

Dopplergrams made in C IV 1548 A are studied for evidence of velocity shear near H-alpha dark filaments and for large-scale flow convergent on active regions. The three regions studied support earlier conclusions that shear is a common property of active regions and that active regions may be the foci of converging plasma flow. Flow patterns near filaments show divergence or convergence as well as shear. Also the sense of the shear can be either cyclonic or anticyclonic. No preference is noted for convergence or divergence or for a particular sense of shear, and there appears to be no correlation between the sense of the shear and the sign of the velocity gradient normal to the filament. The close association of H-alpha dark filaments with shear lines leads to the suggestion that the filaments may arise from a cooling instability induced by the Bernoulli effect.