Correlation between the solar magnetic field strength and the millimeter brightness temperature

TL;DR

This study explores the relationship between solar magnetic field strength and millimeter brightness temperature using ALMA and SDO/HMI data, revealing region-specific correlations explained by thermal bremsstrahlung.

Contribution

It provides the first detailed analysis of the correlation between magnetic fields and brightness temperature at 1.2 mm on the Sun.

Findings

Chromospheric network and active regions show positive correlation.

Sunspots exhibit negative correlation.

Quiet Sun regions show no correlation.

Abstract

Images of the Sun at millimeter wavelengths obtained by ALMA show a significant correspondence with the magnetograms. In this paper, we investigate this correspondence by comparing ALMA full-disk solar image taken at 1.2 mm with a SDO/HMI magnetogram and analyze their correlation. It is found that chromospheric network and active regions show a positive correlation where brightness temperature is increasing with the line-of-sight magnetic field strength, while sunspots have a negative correlation. Quiet Sun regions do not show any dependence of the brightness temperature with the magnetic field. Thermal bremsstrahlung is given as the best explanation for the observed correlations.