Solar Coronal Loops Associated with Small-scale Mixed Polarity Surface Magnetic Fields

TL;DR

This study reveals that small-scale mixed polarity magnetic fields at the footpoints of coronal loops play a key role in flux cancellation and reconnection, contributing to mass and energy supply in the solar corona.

Contribution

It provides high-resolution observational evidence linking small-scale magnetic interactions at loop footpoints to coronal heating processes.

Findings

Coronal loops are rooted near minor opposite-polarity magnetic elements.

Flux cancellation and reconnection occur at loop footpoints.

Inverse Y-shaped jets are observed during flux cancellation.

Abstract

How and where are coronal loops rooted in the solar lower atmosphere? The details of the magnetic environment and its evolution at the footpoints of coronal loops are crucial to understanding the processes of mass and energy supply to the solar corona. To address the above question, we use high-resolution line-of-sight magnetic field data from the Imaging Magnetograph eXperiment instrument on the SUNRISE balloon-borne observatory and coronal observations from the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory of an emerging active region. We find that the coronal loops are often rooted at the locations with minor small-scale but persistent opposite-polarity magnetic elements very close to the larger dominant polarity. These opposite-polarity small-scale elements continually interact with the dominant polarity underlying the coronal loop through flux cancellation. At these locations we detect small inverse Y-shaped jets in chromospheric Ca II H images obtained from the SUNRISE Filter Imager during the flux cancellation. Our results indicate that magnetic flux cancellation and reconnection at the base of coronal loops due to mixed polarity fields might be a crucial feature for the supply of mass and energy into the corona.