The Evolution of Coronal Holes over Three Solar Cycles Using the McIntosh Archive
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The Evolution of Coronal Holes over Three Solar Cycles Using the McIntosh Archive Ian M. Hewins1 · Sarah E. Gibson2 · David F. Webb1 · Robert H. McFadden1 · Thomas A. Kuchar1 · Barbara A. Emery1,2 · Scott W. McIntosh2
Received: 23 April 2020 / Accepted: 31 October 2020 © Springer Nature B.V. 2020
Abstract 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. Keywords Coronal holes - solar cycle · Observations - sunspots · Magnetic fields
B I.M. Hewins
[email protected] S.E. Gibson [email protected] D.F. Webb [email protected] R.H. McFadden [email protected] T.A. Kuchar [email protected] B.A. Emery [email protected] S.W. McIntosh [email protected]
1
Institute for Scientific Research, Boston College, Chestnut Hill, MA, USA
2
High Altitude Observatory, National Center for Atmospheric Research, Boulder, CO, USA
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Figure 1 The McIntosh Archive (McA) synoptic maps are a global representation of the evolving solar magnetic field. Each map covers 360◦ of a Carrington rotation. The extra 30◦ on either side overlaps with the previous and following maps. Magnetic features are identified by a distinct color: Blue represents positive-polarity coronal holes, red represents negative coronal holes, pale blue represents areas of dominant positive polarity, gray represents areas of dominant negative polarity, dark green represents filaments, light green represents polarity inversion lines, dark orange represents positive polarity sunspots, light orange represents negative polarity sunspots and (small) yellow spots represent plage regions. The full archive is publicly available at www2.hao.ucar.edu/mcintosh-archive/four-cycles-solar-synoptic-maps.
1. Introduction In 1964 (the beginning of Solar Cycle 20), Patrick McIntosh began creating hand-drawn synoptic maps of solar magnetic features, based on Hα images (Figure 1). Using magnetograms, he included magnetic polarity inversion lines that connected filaments separated by many degrees, thus establishing the polarity of other features such as sunspots and plage and revealing the large-scale organization of the solar magnetic field (McIntosh, 1979). Coronal holes were eventually included using ground-based He 10830 Å images from the National Solar Observatory (NSO) Kitt Peak starting in 1981 and later (after 1992) from NSO’s Sacramento Peak. Note, Mc
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