The formation and disintegration of magnetic bright points observed by Sunrise/IMaX

TL;DR

This study investigates the physical evolution of magnetic bright points in the quiet Sun, revealing complex formation and disintegration processes, with evidence of convective collapses and dynamic magnetic field changes observed through high-resolution solar imaging.

Contribution

It provides detailed observational analysis of MBP evolution, highlighting the role of convective collapses and dynamic flows, and offers statistical insights into their magnetic field strength changes.

Findings

MBPs form through strengthening of equipartition fields with moderate downflows.

Strong downdrafts (~2.4 km/s) are associated with MBP evolution.

Approximately 30% of MBPs reach kG magnetic field strengths.

Abstract

The evolution of the physical parameters of magnetic bright points (MBPs) located in the quiet Sun (mainly in the interwork) during their lifetime is studied. First we concentrate on the detailed description of the magnetic field evolution of three MBPs. This reveals that individual features follow different, generally complex, and rather dynamic scenarios of evolution. Next we apply statistical methods on roughly 200 observed MBP evolutionary tracks. MBPs are found to be formed by the strengthening of an equipartition field patch, which initially exhibits a moderate downflow. During the evolution, strong downdrafts with an average velocity of 2.4 km/s set in. These flows, taken together with the concurrent strengthening of the field, suggest that we are witnessing the occurrence of convective collapses in these features, although only 30% of them reach kG field strengths. This fraction might turn out to be larger when the new 4 m class solar telescopes are operational as observations of MBPs with current state of the art instrumentation could still be suffering from resolution limitations. Finally, when the bright point disappears (although the magnetic field often continues to exist) the magnetic field strength has dropped to the equipartition level and is generally somewhat weaker than at the beginning of the MBP's evolution. Noteworthy is that in about 10% of the cases we observe in the vicinity of the downflows small-scale strong (exceeding 2 km/s) intergranular upflows related spatially and temporally to these downflows.