Nonlinear force-free field modeling of a solar active region using SDO/HMI and SOLIS/VSM data

TL;DR

This study models the solar coronal magnetic field using data from SDO/HMI and SOLIS/VSM, demonstrating the robustness of the nonlinear force-free field algorithm despite differences in input data.

Contribution

It compares coronal magnetic field reconstructions from two different data sources, accounting for measurement uncertainties and validating the modeling approach.

Findings

Models show considerable similarity despite different input data.

The algorithm is robust against data differences and deficiencies.

Quantitative differences in magnetic energy and force metrics are characterized.

Abstract

We use SDO/HMI and SOLIS/VSM photospheric magnetic field measurements to model the force-free coronal field above a solar active region, assuming magnetic forces to dominate. We take measurement uncertainties caused by, e.g., noise and the particular inversion technique into account. After searching for the optimum modeling parameters for the particular data sets, we compare the resulting nonlinear force-free model fields. We show the degree of agreement of the coronal field reconstructions from the different data sources by comparing the relative free energy content, the vertical distribution of the magnetic pressure and the vertically integrated current density. Though the longitudinal and transverse magnetic flux measured by the VSM and HMI is clearly different, we find considerable similarities in the modeled fields. This indicates the robustness of the algorithm we use to calculate the nonlinear force-free fields against differences and deficiencies of the photospheric vector maps used as an input. We also depict how much the absolute values of the total force-free, virial and the free magnetic energy differ and how the orientation of the longitudinal and transverse components of the HMI- and VSM-based model volumes compares to each other.