On the fine structure of the sunspot penumbrae. III The vertical extension of penumbral filaments

TL;DR

This study uses spectropolarimetric data and the uncombed model to analyze the fine vertical structure of penumbral filaments in sunspots, revealing flux tubes 100-300 km thick.

Contribution

It demonstrates that the uncombed model accurately reproduces spectropolarimetric observations, providing detailed estimates of penumbral flux tube vertical extension.

Findings

Flux tubes are 100-300 km thick vertically.

The uncombed model reproduces observed Stokes V asymmetries.

Physical quantities show similar radial dependence across lines.

Abstract

In this paper we study the fine structure of the penumbra as inferred from the uncombed model (flux tube embedded in a magnetic surrounding) when applied to penumbral spectropolarimetric data from the neutral iron lines at 6300 \AA. The inversion infers very similar radial dependences in the physical quantities (LOS velocity, magnetic field strength etc) as those obtained from the inversion of the Fe I 1.56 $\mu$m lines. In addition, the large Stokes $V$ area asymmetry exhibited by the visible lines helps to constrain the size of the penumbral flux tubes. As we demonstrate here, the uncombed model is able to reproduce the area asymmetry with striking accuracy, returning flux tubes as thick as 100-300 kilometers in the vertical direction, in good agreement with previous investigations.