Spectral Analysis of Sunspot Penumbrae Observed with HINODE

TL;DR

This study uses spectral and polarimetric data from HINODE to analyze small-scale plasma flows in sunspot penumbrae, revealing detailed flow patterns associated with the Evershed effect.

Contribution

It provides a high-resolution analysis of the vertical flow components in sunspot penumbrae, highlighting the spatial distribution of up- and down-flows related to filament structures.

Findings

Vertical Evershed flow dominates near disk center

Up-flows are concentrated at bright filament heads

Down-flows are located at the penumbral side of filaments

Abstract

To investigate the penumbral plasma flow on a small scale, spectropolari- metric data of sunspots recorded by HINODE was used. Maps of Doppler velocities were created by evaluating the bisector in the line-wing, thereby visualizing the flow pattern in the low photosphere where the Evershed effect is most pronounced. In penumbrae close to the disk center, the vertical component of the Evershed flow dominates. The latter consists of a series of elongated up-flow patterns extending radially through the entire center-side penumbra at a constant azimuth. Along this structure, strong up-flows appear in concentrated patches separated by weaker up-flows or even down-flows. The strong up-flows appear at the bright heads and the umbral side of the dark-core of the filament, while the down-flows are rather located at the penumbral side of the filament. Projection effects lead to an overall red-shift of the limb- side penumbra, but the described pattern of up- and down-flows is still ascertainable.