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

TL;DR

This paper improves solar coronal magnetic field modeling by optimizing Outflow Fields, which incorporate solar wind effects, resulting in more accurate magnetic topology and flux measurements compared to traditional PFSS models.

Contribution

It introduces an optimized Outflow Field model with enhanced accuracy and realism, validated against multiple observational data sources, and provides a new Python package for community use.

Findings

Reduced discrepancy with in-situ magnetic field measurements from 45% to 24%.

Accurately captures magnetic field topology during eclipses.

Improved solar wind solution model.

Abstract

We expand upon our paper (Rice and Yeates, 2021) which introduced `Outflow Fields': alternatives to the widely-used potential field source surface (PFSS) extrapolations of the Sun's coronal magnetic field which 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 (OSF) 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. This includes 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".