Spectroscopic Analysis of an EIT Wave/Dimming Observed by Hinode/EIS

TL;DR

This study uses Hinode/EIS spectroscopic data to analyze an EIT wave and associated dimming, revealing plasma outflows and increased spectral line widths at the dimming edges, supporting the field line stretching model.

Contribution

It provides spectroscopic evidence of plasma dynamics and line broadening in EIT wave dimmings, supporting the field line stretching interpretation.

Findings

Significant blue shifts indicating plasma outflows in dimming regions

Line widths increase at the outer edge of the dimmings

Results support the field line stretching model for EIT waves

Abstract

EIT waves are a wavelike phenomenon propagating outward from the coronal mass ejection (CME) source region, with expanding dimmings following behind. We present a spectroscopic study of an EIT wave/dimming event observed by Hinode/EIS. Although the identification of the wave front is somewhat affected by the pre-existing loop structures, the expanding dimming is well defined. We investigate the line intensity, width, and Doppler velocity for 4 EUV lines. In addition to the significant blue shift implying plasma outflows in the dimming region as revealed in previous studies, we find that the widths of all the 4 spectral lines increase at the outer edge of the dimmings. We illustrate that this feature can be well explained by the field line stretching model, which claims that EIT waves are apparently moving brightenings that are generated by the successive stretching of the closed field lines.