Can an Unobserved Concentration of Magnetic Flux Above the Poles of the Sun Resolve the Open Flux Problem?

Global models of the extended solar corona, driven by observed photospheric magnetic fields, generally cannot reproduce the amplitude of the measured interplanetary magnetic field at 1 au (or elsewhere in the heliosphere), often underestimating it by a factor of two or more. Some modelers have attem...

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Bibliographic Details
Published in:The Astrophysical journal Vol. 884; no. 1; pp. 18 - 29
Main Authors: Riley, Pete, Linker, Jon A., Mikic, Zoran, Caplan, Ronald M., Downs, Cooper, Thumm, Jean-Luc
Format: Journal Article
Language:English
Published: Philadelphia The American Astronomical Society 10.10.2019
IOP Publishing
Subjects:
Astrophysics
Computational fluid dynamics
Corona
Coronal holes
Fluctuations
Fluid flow
Ground-based observation
Heliosphere
Interplanetary magnetic field
Interplanetary magnetic fields
Latitude
Magnetic fields
Magnetic flux
Magnetohydrodynamic models
Magnetohydrodynamical simulations
Magnetohydrodynamics
Observatories
Photosphere
Photospheric magnetic fields
Potential fields
Solar corona
Solar coronal holes
Solar coronal streamers
Solar magnetic field
Solar Orbiter (ESA)
Solar orbits
Solar photosphere
Spacecraft
Sun
ISSN:0004-637X, 1538-4357
Online Access:Get full text
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Summary:Global models of the extended solar corona, driven by observed photospheric magnetic fields, generally cannot reproduce the amplitude of the measured interplanetary magnetic field at 1 au (or elsewhere in the heliosphere), often underestimating it by a factor of two or more. Some modelers have attempted to resolve this "open flux" problem by adjusting what they believe to be errors in the estimates of the photospheric field values. Others have simply multiplied interplanetary estimates by some correction factor to match 1 au values. Here, we investigate whether this "missing" flux can be explained by a source of largely unobserved, concentrated bundles of flux in the photosphere at latitudes too high to be adequately resolved by ground-based observatories or Earth-based spacecraft. Using potential field source-surface and magnetohydrodynamic models, we demonstrate that this additional polar flux can (at least partially) resolve the open flux problem, without generating any new observational discrepancies. For example, we show that model solutions without this additional flux systematically produce streams lying at higher hello-latitudes than is inferred from observations. More importantly, adding this polar flux to the models does not substantially change the location or size of computed coronal holes. The upcoming joint ESA/NASA Solar Orbiter mission may be able to support or refute this idea.
Bibliography:AAS19197
The Sun and the Heliosphere
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ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/ab3a98