On the Possibility to Diagnose the Non-Maxwellian κ-Distributions from the Hinode/EIS EUV Spectra

Abstract

We investigate the possibility to diagnose the κ-distributions from the EUV spectra observed by the Hinode/EIS spectrometer. Observable lines of the most abundant elements except Fe are considered. Synthetic spectra for the κ-distributions with κ=2 – 10 and the Maxwellian distribution were calculated for a range of temperatures and electron densities. We find that only a small number of O, S, Ca, and Ni line ratios are sensitive to κ. A list of the best diagnostic options using transition region and coronal lines is provided. Usually, the line ratios sensitive to κ are also sensitive to electron density. Weak O iv lines are a notable exception. These lines offer greatest sensitivity to κ from all the lines observed by Hinode/EIS. Density diagnostics using lines of the non-Fe elements is discussed and the influence of κ on the diagnostics of electron density is presented. The density diagnostics using these non-Fe EIS lines are strongly affected by both known and unknown blends. Therefore, we performed the density diagnostics using the Fe xii – xiv lines. Subsequently, these proposed diagnostic methods for κ-distributions are tested using the spectral atlas obtained by Brown et al. (Astrophys. J. Suppl. 176, 511, 2008). These data do not provide conclusive evidence for the presence of κ-distributions due to possible plasma multitermality, a low observed signal-to-noise ratio, and unremovable or unknown blends.