Emergence of magnetic flux sheets in the quiet Sun. I. Statistical properties

TL;DR

This study statistically analyzes the emergence of magnetic flux sheets in the quiet Sun, revealing their frequency, properties, and association with granular phenomena, thus enhancing understanding of small-scale solar magnetic activity.

Contribution

It introduces a novel two-step method to identify and analyze magnetic flux sheet emergence events using spectro-polarimetric data, providing new insights into their occurrence and dynamics.

Findings

42 flux sheet emergence events identified

Flux sheets often associated with nascent and exploding granules

Recycled magnetic flux from downflows may facilitate emergence

Abstract

Small-scale magnetic flux emergence in the quiet Sun is crucial for maintaining solar magnetic activity. On the smallest scales studied so far, namely within individual granules, two mechanisms have been identified: emergence in tiny magnetic loops and emergence in the form of magnetic flux sheets covering the granule. While there are abundant observations of tiny magnetic loops within granules, the evidence for the emergence of granule-covering magnetic sheets is much more limited. This work aims to statistically analyze magnetic flux sheets, quantify their frequency on the solar surface and their potential contribution to the solar magnetic budget in the photosphere, and investigate the plasma dynamics and granular-scale phenomena associated with their emergence. Using spectro-polarimetric datasets from the solar optical telescope aboard the Hinode satellite and the ground-based Swedish Solar telescope, we developed a two-step method to identify magnetic flux sheet emergence events, detecting magnetic flux patches based on the calculation of the transverse and longitudinal magnetic flux density and associating them with their host granules based on velocity field analysis. We identified 42 events of magnetic flux sheet emergence and characterized their magnetic properties and the associated plasma dynamics of their host granules. Our results align with numerical simulations, indicating a similar occurrence rate. We investigated the relationship between magnetic flux emergence and granular phenomena, finding that flux sheets often emerge in association with standard nascent granules, as well as exploding granules, or granules with granular lanes. In particular, we highlight the potential role of recycled magnetic flux from downflow regions in facilitating flux sheet emergence.