Abstract
Abstract The potential field (PF) solution of the solar corona is a vital modeling tool for a wide range of applications, including minimum energy estimates, coronal magnetic field modeling, and empirical solar wind solutions. Given its popularity, it is important to understand how choices made in computing a PF may influence key properties of the solution. Here we study PF solutions for the global coronal magnetic field on 2012 June 13, computed with our high-performance finite-difference code POT3D. Solutions are analyzed for their global properties and locally around NOAA AR 11504, using the net open flux, open-field boundaries, total magnetic energy, and magnetic structure as metrics. We explore how PF solutions depend on (1) the data source, type, and processing of the inner boundary conditions; (2) the choice of the outer boundary condition height and type; and (3) the numerical resolution and spatial scale of information at the lower boundary. We discuss the various qualitative and quantitative differences that naturally arise by using different maps as input, and we illustrate how coronal morphology and open flux depend most strongly on the outer boundary condition. We also show how large-scale morphologies and the open magnetic flux are remarkably insensitive to model resolution, while the surface mapping and embedded magnetic complexity vary considerably. This establishes important context for past, current, and future applications of the PF for coronal and solar wind modeling.
Highlights
The simplest description of the coronal magnetic field, based on a photospheric boundary radial magnetic field, is a potential field model
The paper is outlined as follows: In Sec. 2 we describe how global coronal potential field (PF) solutions are computed with the POT3D code
VARIATIONS IN RESOLUTION Here we investigate how the PF solutions change based on the resolution of the magnetogram and the corresponding 3D domain
Summary
The simplest description of the coronal magnetic field, based on a photospheric boundary radial magnetic field, is a potential (current-free) field model. A comparison of finite-difference PF solutions for CR2144 (approximately a year and a half from our target date) was performed in Hayashi et al (2016) using various observatory data, flux balancing methods, and smoothing filters, with a constant resolution and boundary condition Their focus was on comparisons to observations, such as EUV coronal holes to the open field, and OMNI magnetic data to the open flux. POTENTIAL FIELD SOLUTIONS WITH POT3D POT3D is a Fortran code that computes potential field solutions to approximate the solar coronal magnetic field using observed photospheric magnetic fields as a boundary condition It is used for computing Open Field and PFCS models (see Appendix A for details).
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