Coronal magnetic field and emission properties of small-scale bright and faint loops in the quiet Sun

TL;DR

This study statistically analyzes the magnetic and emission properties of small-scale bright and faint loops in the quiet Sun, revealing their non-potential magnetic fields and the correlation between loop characteristics and magnetic field strength.

Contribution

It introduces an automatic magneto-hydro-static modeling tool to match magnetic field lines with observed small-scale loops, providing new insights into their magnetic structure and energy release mechanisms.

Findings

Magnetic fields in loops are non-potential.

Loops below 1.5 Mm are flatter, indicating plasma pressure effects.

Strong correlation (0.9) between loop height and length.

Abstract

The present study provides statistical information on the coronal magnetic field and intensity properties of small-scale bright and faint loops in the quiet Sun. We aim to quantitatively investigate the morphological and topological properties of the coronal magnetic field in bright and faint small-scale loops, with the former known as coronal bright points (CBPs). We analyse 126 small-scale loops using quasi-temporal imaging and line-of-sight magnetic field observations. We employ a recently developed automatic tool that uses a linear magneto-hydro-static model to compute the magnetic field in the solar atmosphere and automatically match individual magnetic field lines with small-scale loops. For most of the loops, we automatically obtain an excellent agreement of the magnetic field lines from the LMHS model and the loops seen in AIA 193 A. One stand-out result is that the magnetic field is non-potential. We obtain the typical ranges of loop heights, lengths, intensities, mean magnetic field strength along the loops and at loop tops, and magnetic field strength at loop footpoints. We find that loops below the classic chromospheric height of 1.5 Mm are flatter suggesting that non-magnetic forces (one of which is the plasma pressure) play an important role below this height. We find a strong correlation (Pearson coefficient of 0.9) between loop heights and lengths. The average intensity along the loops correlates stronger with the average magnetic field along the loops than with the field strength at loop tops. The latter correlation indicates that the energy release in the loops is more likely linked to the average magnetic field along the loops than the field strength on the loop tops. In other words, the energy is probably released all along the loops, but not just at the loop top. This result is consistent with the recent benchmarking radiative 3D MHD model of N\'obrega-Siberio etal.