The size distribution of magnetic bright points derived from Hinode/SOT observations

TL;DR

This study analyzes the size distribution of Magnetic Bright Points in the solar photosphere using Hinode/SOT data, developing an automated method to measure their diameters, which are consistent with previous findings but limited by observational resolution.

Contribution

A new automated segmentation algorithm was developed to accurately determine MBP sizes from Hinode/SOT G-band images, revealing the impact of spatial sampling on size measurements.

Findings

Mean MBP diameter is approximately 218 km at 0.108 arcsec/pixel sampling.

At higher resolution (0.054 arcsec/pixel), the mean diameter is about 166 km.

Current observations cannot resolve the smallest magnetic elements in the photosphere.

Abstract

Context. Magnetic Bright Points (MBPs) are small-scale magnetic features in the solar photosphere. They may be a possible source of coronal heating by rapid footpoint motions that cause magnetohydrodynamical waves. The number and size distribution are of vital importance in estimating the small scale-magnetic-field energy. Aims. The size distribution of MBPs is derived for G-band images acquired by the Hinode/SOT instrument. Methods. For identification purposes, a new automated segmentation and identification algorithm was developed. Results. For a sampling of 0.108 arcsec/pixel, we derived a mean diameter of (218 +- 48) km for the MBPs. For the full resolved data set with a sampling of 0.054 arcsec/pixel, the size distribution shifted to a mean diameter of (166 +- 31) km. The determined diameters are consistent with earlier published values. The shift is most probably due to the different spatial sampling. Conclusions. We conclude that the smallest magnetic elements in the solar photosphere cannot yet be resolved by G-band observations. The influence of discretisation effects (sampling) has also not yet been investigated sufficiently.