Solar Mean Magnetic Field of the Chromosphere

TL;DR

This study analyzes the Solar Mean Magnetic Field at the chromosphere using spectropolarimetric data, revealing it is weaker than at the photosphere but highly correlated, supporting its role as the IMF source.

Contribution

It extends SMMF analysis from the photosphere to the chromosphere using new spectropolarimetric measurements from SOLIS/VSM.

Findings

Chromospheric SMMF is 60% of the photospheric SMMF.

Pearson correlation coefficient between chromospheric and photospheric SMMF is 0.80.

Chromospheric SMMF supports its role as the source of the IMF.

Abstract

The Solar Mean Magnetic Field (SMMF) is the mean value of the line of sight (LOS) component of the solar vector magnetic field averaged over the visible hemisphere of the Sun. So far, the studies on SMMF have mostly been confined to the magnetic field measurements at the photosphere. In this study, we calculate and analyse the SMMF using magnetic field measurements at the chromosphere, in conjunction with that of photospheric measurements. For this purpose, we have used full disk LOS magnetograms derived from spectropolarimetric observations carried out in Fe I 630.15 nm and Ca II 854.2 nm by the Synoptic Optical Long term Investigations of the Sun (SOLIS)/Vector Spectromagnetograph (VSM) instrument during 2010 to 2017. It is found from this study that the SMMF at the chromosphere is weaker by a factor of 0.60 compared to the SMMF at the upper photosphere. The correlation analysis between them gives a Pearson correlation coefficient of 0.80. The similarity and reduced intensity of the chromospheric SMMF with respect to the photospheric SMMF corroborate the idea that it is the source of the Interplanetary Magnetic Field (IMF).