Influence of Non-Potential Coronal Magnetic Topology on Solar-Wind Models
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By comparing a magneto-frictional model of the low-coronal magnetic-field to a potential-field source-surface model, we investigate the possible impact of non-potential magnetic structure on empirical solar-wind models. These empirical models (such as Wang–Sheeley–Arge) estimate the distribution of solar-wind speed solely from the magnetic-field structure in the low corona. Our models are computed in a domain between the solar surface and 2.5 solar radii, and they are extended to 0.1 AU using a Schatten current-sheet model. The non-potential field has a more complex magnetic skeleton and quasi-separatrix structures than the potential field, leading to different sub-structure in the solar-wind speed proxies. It contains twisted magnetic structures that can perturb the separatrix surfaces traced down from the base of the heliospheric current sheet. A significant difference between the models is the greater amount of open magnetic flux in the non-potential model. Using existing empirical formulae this leads to higher predicted wind speeds for two reasons: partly because magnetic-flux tubes expand less rapidly with height, but more importantly because more open-field lines are further from coronal-hole boundaries.
KeywordsCorona, models Magnetic fields, corona Magnetic fields, interplanetary Magnetic fields, models Solar wind, theory
A.R. Yeates and S.J. Edwards were supported by STFC through consortium grant ST/K001043/1 and the Durham University Impact Acceleration Account, as well as by the US Air Force Office for Scientific Research. D.H. Mackay would like to thank the Leverhulme Trust and STFC for financial support. The authors thank Andrew L. Haynes for the use of his separatrix surface and null-point finding codes. Numerical simulations used the SRIF and STFC funded HPC cluster at the University of St Andrews.
Conflict of interest
The authors declare that they have no conflicts of interest.
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