CHIANTI - An atomic database for emission lines. X. Spectral atlas of a cold feature observed with Hinode/EIS

TL;DR

This paper presents a spectral atlas of a cold, bright active region observed with Hinode/EIS, testing CHIANTI atomic data against observed emission lines and identifying new spectral lines.

Contribution

The study develops a spectral atlas for transition region ions and evaluates CHIANTI atomic data accuracy using new solar spectral observations.

Findings

Identification of several previously unobserved lines in solar spectra.

Excellent agreement between CHIANTI predictions and observed line intensities.

Validation of atomic data for transition region ions.

Abstract

In this work we report on a cold, bright portion of an active region observed by Hinode/EIS. The emitting plasma was very bright at transition region temperatures, and the intensities of lines of ions formed between 10^5-10^6 K were enhanced over normal values. The data set constitutes an excellent laboratory where the emission of transition region ions can be tested. We first determine the thermal structure of the observed plasma, and then we use it 1) to develop a spectral atlas, and 2) to assess the quality of CHIANTI atomic data by comparing predicted emissivities with observed intensities. We identify several lines never observed before in solar spectra, and find an overall excellent agreement between CHIANTI predicted emissivities and observations.