Variations of magnetic bright point properties with longitude and latitude as observed by Hinode/SOT G-band data

TL;DR

This study analyzes how magnetic bright point properties vary with solar longitude and latitude using Hinode/SOT G-band data, revealing size increases and brightness decreases towards the limb, with implications for understanding solar magnetic features.

Contribution

It provides a detailed characterization of the centre-to-limb variation of MBP size and brightness, including polynomial fits and distribution analysis, which was not previously documented.

Findings

MBP sizes increase from solar centre to limb.

MBP intensities decrease towards the limb.

Size distribution follows a log-normal function.

Abstract

Small-scale magnetic fields can be observed on the Sun in high resolution G-band filtergrams as magnetic bright points (MBPs). We study Hinode/ Solar Optical Telescope (SOT) longitude and latitude scans of the quiet solar surface taken in the G-band in order to characterise the centre-to-limb dependence of MBP properties (size and intensity). We find that the MBP's sizes increase and their intensities decrease from the solar centre towards the limb. The size distribution can be fitted using a log-normal function. The natural logartihm of the mean (parameter \mu) of this function follows a second-order polynomial and the generalised standard deviation (parameter \sigma) follows a fourth-order polynomial or equally well (within statistical errors) a sine function. The brightness decrease of the features is smaller than one would expect from the normal solar centre-to-limb variation; that is to say, the ratio of a MBP's brightness to the mean intensity of the image increases towards the limb. The centre-to-limb variations of the intensities of the MBPs and the quiet-Sun field can be fitted by a second order polynomial. The detailed physical process that results in an increase of a MBP's brightness and size from Sun centre to the limb is not yet understood and has to be studied in more detail in the future.