Global Coronal Equilibria with Solar Wind Outflow. II. Optimizing the Outflow Model

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Abstract
We expand upon our 2021 paper that introduced “outflow fields”: alternatives to the widely used potential field source surface (PFSS) extrapolations of the Sun’s coronal magnetic field that take into account the effect of the solar wind. We showed that our fields have several advantages over PFSS, namely more accurate measurements of the open solar flux relative to observations, more realistic streamer shapes, and less dependence on the arbitrary source surface height. In this paper we seek to quantify these improvements. These include comparison of magnetic field line angles with eclipse photography, an improved solar wind solution model, and the introduction of data from a wider range of observations. We use these comparisons to determine the optimum parameters for our model using an evolutionary algorithm, in addition to the creation of synthetic eclipse images. We find that our outflow fields can accurately capture the overall topology of the magnetic field, and reduce the well-known discrepancy with in situ magnetic field measurements by a significant margin relative to PFSS. Specifically, over the period between 2000 and 2022 for a typical source surface height we find that optimized outflow fields reduce this discrepancy from around 45% to 24% while also matching the field line topology seen during eclipse photography. Our model is presented for wider use by the community as a new Python package “outflowpy.”
Funding Information
  • UKRI ∣ Science and Technology Facilities Council (UKRI1216)

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