Magnetic Field Strength and Inclination in the Penumbral Fine-Structure

TL;DR

This study reveals a strong correlation between magnetic field strength, inclination, and brightness in sunspot penumbra, showing darker lanes have stronger, flatter fields, based on high-resolution spectral analysis of the Fe I 6842.7 line.

Contribution

It provides new insights into the magnetic structure of penumbral fine-structure by using high-resolution spectra and a specific spectral line, clarifying the relationship between magnetic properties and brightness.

Findings

Darker penumbral lanes host 10% stronger magnetic fields.

These fields are more than 30 degrees flatter in inclination.

The correlation is specific to the Fe I 6842.7 line and deep layers.

Abstract

The uncertainty about a possible correlation between strength and inclination of the magnetic field and the continuum intensity of the sunspot penumbral fine-structure has been removed by a detailed analysis of a spatially very high resolved spectrum: the darker, lengthy penumbral lanes host a 10% stronger and >30 deg flatter magnetic field as compared to the bright penumbral locations. This finding does not only result from the high spatial resolution but also from the choice of the Fe I 6842.7 line, which obtains its essential contribution from those deep layers near the continuum intensity level where the penumbral structure is seen. The almost perfect correlation establishes that the penumbral structure is formed by two magnetic components mainly differing by their field inclination. The discrepancy with results from other Zeeman lines, as e.g. Fe I 6302.5, indicates a different field structure above the white light penumbral layers.