Emergence of small-scale magnetic loops through the quiet solar atmosphere

TL;DR

This study observes the emergence of small-scale magnetic loops in the quiet Sun, revealing their formation, dynamics, and partial ascent into the chromosphere, contributing to understanding solar magnetic flux processes.

Contribution

It provides the first detailed observational analysis of small-scale magnetic loop emergence and their evolution from photosphere to chromosphere in the quiet Sun.

Findings

Approximately 0.02 loops per hour per arcsec^2 emerge.

23% of loops reach the chromosphere, producing brightness enhancements.

Emerging loops often violate Hale's polarity rules.

Abstract

We investigate the emergence of magnetic flux in the quiet Sun at very small spatial scales, focusing on the magnetic connection between the photosphere and chromosphere. The observational data consist of spectropolarimetric measurements and filtergrams taken with the Hinode satellite and the Dutch Open Telescope. We find that a significant fraction of the magnetic flux present in internetwork regions appears in the form of Omega-shaped loops. The emergence rate is 0.02 loops per hour and arcsec^{-2}, which brings 1.1 x 10^12 Mx s^{-1} arcsec^{-2} of new flux to the solar surface. Initially, the loops are observed as small patches of linear polarization above a granular cell. Shortly afterwards, two footpoints of opposite polarity become visible in circular polarization within or at the edges of the granule and start to move toward the adjacent intergranular space. The orientation of the footpoints does not seem to obey Hale's polarity rules. The loops are continuously buffeted by convective motions, but they always retain a high degree of coherence. Interestingly, 23% of the loops that emerge in the photosphere reach the chromosphere (16 cases out of 69). They are first detected in Fe I 630 nm magnetograms and 5 minutes later in Mg I b 517.3 nm magnetograms. After about 8 minutes, some of them are also observed in Ca II H line-core images, where the footpoints produce small brightness enhancements.