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

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.