The Evolution of Coronal Holes over Three Solar Cycles Using the McIntosh Archive

Using the McIntosh Archive of solar features, we analyze the evolution of coronal holes over more than three solar cycles. We demonstrate that coronal-hole positions and lifetimes change significantly on time scales from months to years, and that the pattern of these changes is clearly linked to the solar-activity cycle. We demonstrate that the lifetimes of low-latitude coronal holes are usually less than one rotation but may extend to almost three years. When plotted over time, the positions of low-latitude coronal holes that remain visible for over one rotation track the sunspot butterfly diagram in terms of their positions on the Sun over a solar cycle. Finally, we confirm that coronal holes do not in general rigidly rotate.