Magnetic loops in the quiet Sun

TL;DR

This study analyzes the magnetic field structure of the quiet Sun using high-resolution measurements and extrapolation techniques, revealing that most magnetic loops reaching the chromosphere originate from strong photospheric foot points and are highly dynamic.

Contribution

It provides detailed insights into the magnetic loop configurations in the quiet Sun using unprecedented spatial resolution data and advanced extrapolation methods.

Findings

91% of magnetic energy in the mid chromosphere is in loops with strong foot points (>300 G).

Most loops are asymmetric with weaker foot points in the internetwork.

Loops reaching the chromosphere are expected to be highly dynamic with short lifetimes.

Abstract

We investigate the fine structure of magnetic fields in the atmosphere of the quiet Sun. We use photospheric magnetic field measurements from {\sc Sunrise}/IMaX with unprecedented spatial resolution to extrapolate the photospheric magnetic field into higher layers of the solar atmosphere with the help of potential and force-free extrapolation techniques. We find that most magnetic loops which reach into the chromosphere or higher have one foot point in relatively strong magnetic field regions in the photosphere. $91%$ of the magnetic energy in the mid chromosphere (at a height of 1 Mm) is in field lines, whose stronger foot point has a strength of more than 300 G, i.e. above the equipartition field strength with convection. The loops reaching into the chromosphere and corona are also found to be asymmetric in the sense that the weaker foot point has a strength $B < 300$ G and is located in the internetwork. Such loops are expected to be strongly dynamic and have short lifetimes, as dictated by the properties of the internetwork fields.