The Analysis of Penumbral Fine Structure Using an Advanced Inversion Technique

TL;DR

This paper introduces a novel spectropolarimetric inversion method to resolve and analyze the fine structure of penumbral filaments in sunspots, revealing detailed plasma parameter variations.

Contribution

It demonstrates the first application of one-component inversion codes to resolved penumbral filaments using Hinode data, enabling direct association of plasma stratifications with fine structures.

Findings

We observe weaker and more horizontal magnetic fields in bright filaments' low layers.

Line-of-sight velocities are increased in bright filaments.

Results in the mid penumbra remain ambiguous, requiring further study.

Abstract

We present a method to study the penumbral fine structure using data obtained by the spectropolarimeter onboard HINODE. For the first time, the penumbral filaments can be considered as resolved in spectropolarimetric measurements. This enables us to use inversion codes with only one-component model atmospheres, and thus assign the obtained stratifications of plasma parameters directly to the penumbral fine structure. This approach is applied to the limb-side part of the penumbra in active region NOAA 10923. The preliminary results show a clear dependence of the plasma parameters on continuum intensity in the inner penumbra, i.e. weaker and horizontal magnetic field along with increased line-of-sight velocity are found in the low layers of the bright filaments. The results in the mid penumbra are ambiguous and future analyses are necessary to unveil the magnetic field structure and other plasma parameters there.