Influence of Non-Potential Coronal Magnetic Topology on Solar-Wind Models

TL;DR

This study compares potential and non-potential coronal magnetic field models to assess their impact on empirical solar-wind speed predictions, revealing that non-potential fields produce more open flux and higher wind speeds due to complex magnetic structures.

Contribution

It demonstrates how non-potential magnetic structures influence solar-wind models, highlighting differences in open flux and wind speed predictions compared to potential field models.

Findings

Non-potential models have more complex magnetic skeletons.

Non-potential models predict higher solar-wind speeds.

More open magnetic flux in non-potential models.

Abstract

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 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.