Comparison of Nonlinear Force-free Field and Potential Field in the Quiet Sun

TL;DR

This study compares potential and three nonlinear force-free magnetic field extrapolations in the quiet Sun, revealing that differences diminish with height but are significant near the photosphere, affecting magnetic field configuration understanding.

Contribution

It provides a detailed comparison of multiple NLFF extrapolation methods against potential fields in the quiet Sun, highlighting their differences and height-dependent behaviors.

Findings

NLFF and potential fields differ mainly in low layers

Differences decrease with height, becoming negligible above 2000 km

Reconstructed NLFF fields deviate significantly from potential fields

Abstract

In this paper, a potential field extrapolation and three nonlinear force-free (NLFF) field extrapolations (optimization, direct boundary integral (DBIE) and approximate vertical integration (AVI) methods) are used to study the spatial configuration of magnetic field in the quiet Sun. It is found that the strength differences between the three NLFF and potential fields exist in the low layers. However, they tend to disappear as the height increases, which are of the order of 0.1 G when the height exceeds $\sim$ 2000 km above the photosphere. The absolute azimuth difference between one NLFF field and the potential field is as follows: for the optimization field, it decreases evidently as the height increases; for the DBIE field, it almost keeps constant and shows no significant change as the height increases; for the AVI field, it increases slowly as the height increases. The analysis shows that the reconstructed NLFF fields deviate significantly from the potential field in the quiet Sun.