Benchmarking atomic data for astrophysics: new EUV flare lines

ABSTRACT Hinode EUV Imaging Spectrometer (EIS) solar spectra of flares are analysed, to benchmark the CHIANTI atomic data in terms of wavelengths and radiances of high-temperature lines. Spectra of two M-class flares are presented and compared to simultaneous spectra of cooler plasma. Using a recent evaluation of the EIS radiometric calibration and an emission measure analysis, overall excellent agreement (to within 10–20 per cent) between predicted and measured radiances of the hot lines is found, confirming in most cases previous identifications based on Skylab observations. Many new line identifications are proposed, in particular for flare lines predicted to be observable but never reported or only observed in laboratory plasma. In several cases, reference wavelengths inconsistent with observation were found. Only few of the hotter lines still need to be identified. Excellent new electron temperature and density diagnostics based on Fe xxiii and Fe xxi have been found. A new Fe xx line is found to contribute significantly to the Solar Orbiter EUV imager for large flares. This study is part of an ongoing work to provide reliable atomic data for present and future missions.