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The Open Flux Problem

Linker, J.A.; Caplan, R.M.; Downs, C.; Riley, P.; Mikic, Z.; Lionello, R.; Henney, C.J.; Arge, C.N.; Liu, Y.; Derosa, M.L.; Yeates, A.; Owens, M.J.

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J.A. Linker

R.M. Caplan

C. Downs

P. Riley

Z. Mikic

R. Lionello

C.J. Henney

C.N. Arge

Y. Liu

M.L. Derosa

M.J. Owens


The heliospheric magnetic field is of pivotal importance in solar and space physics. The field is rooted in the Sun's photosphere, where it has been observed for many years. Global maps of the solar magnetic field based on full-disk magnetograms are commonly used as boundary conditions for coronal and solar wind models. Two primary observational constraints on the models are (1) the open field regions in the model should approximately correspond to coronal holes (CHs) observed in emission and (2) the magnitude of the open magnetic flux in the model should match that inferred from in situ spacecraft measurements. In this study, we calculate both magnetohydrodynamic and potential field source surface solutions using 14 different magnetic maps produced from five different types of observatory magnetograms, for the time period surrounding 2010 July. We have found that for all of the model/map combinations, models that have CH areas close to observations underestimate the interplanetary magnetic flux, or, conversely, for models to match the interplanetary flux, the modeled open field regions are larger than CHs observed in EUV emission. In an alternative approach, we estimate the open magnetic flux entirely from solar observations by combining automatically detected CHs for Carrington rotation 2098 with observatory synoptic magnetic maps. This approach also underestimates the interplanetary magnetic flux. Our results imply that either typical observatory maps underestimate the Sun's magnetic flux, or a significant portion of the open magnetic flux is not rooted in regions that are obviously dark in EUV and X-ray emission.


Linker, J., Caplan, R., Downs, C., Riley, P., Mikic, Z., Lionello, R., …Owens, M. (2017). The Open Flux Problem. Astrophysical Journal, 848(1), Article 70.

Journal Article Type Article
Acceptance Date Sep 2, 2017
Online Publication Date Oct 12, 2017
Publication Date Oct 12, 2017
Deposit Date Oct 17, 2017
Publicly Available Date Oct 19, 2017
Journal Astrophysical Journal
Print ISSN 0004-637X
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 848
Issue 1
Article Number 70
Related Public URLs


Published Journal Article (2.2 Mb)

Copyright Statement
© 2017. The American Astronomical Society. All rights reserved.

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