Coronal holes as indicators of large-scale magnetic fields in the corona

It is shown that coronal holes may be used as indicators to trace the location of the neutral line on the source surface in the corona. At the same time, coronal holes are shown to concentrate in regions of enhanced magnetic field at the source surface. This provides us with a simple method for predicting the interplanetary current sheet and sector structure which, in turn, determine the location of the proton complexes and the outflow regions of high-velocity streams. Rotation of coronal holes has been studied. Rather than being rigid, it displays the same reduced differentiallity as the rest of the corona. However, there are particular periods 2 or 3 years before the cycle minimum when the solid-body type of rotation is settled for both the coronal holes and the corona as a whole.