Coronal Holes and Open Magnetic Flux over Cycles 23 and 24

Chris Lowder; Jiong Qiu; Robert Leamon

doi:10.1007/s11207-016-1041-8

Coronal Holes and Open Magnetic Flux over Cycles 23 and 24

Sol Phys. 2017;292(1):18. doi: 10.1007/s11207-016-1041-8. Epub 2016 Dec 27.

Authors

Chris Lowder^{1

2}, Jiong Qiu², Robert Leamon^{2

3}

Affiliations

¹ 1Department of Mathematical Sciences, Durham University, Durham, DH1 3LE UK.
² 2Department of Physics, Montana State University, Bozeman, MT 59717 USA.
³ 3Department of Astronomy, University of Maryland, College Park, MD 20742 USA.

Abstract

As the observational signature of the footprints of solar magnetic field lines open into the heliosphere, coronal holes provide a critical measure of the structure and evolution of these lines. Using a combination of Solar and Heliospheric Observatory/Extreme ultraviolet Imaging Telescope (SOHO/EIT), Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA), and Solar Terrestrial Relations Observatory/Extreme Ultraviolet Imager (STEREO/EUVI A/B) extreme ultraviolet (EUV) observations spanning 1996 - 2015 (nearly two solar cycles), coronal holes are automatically detected and characterized. Coronal hole area distributions show distinct behavior in latitude, defining the domain of polar and low-latitude coronal holes. The northern and southern polar regions show a clear asymmetry, with a lag between hemispheres in the appearance and disappearance of polar coronal holes.

Keywords: Coronal holes; Magnetic fields, corona; Magnetic fields, models; Solar cycle, models; Solar cycle, observations.