Title:
On diversity of spectral shapes of hydrogen Lyman and Mg II h&k lines observed in a quiescent prominence by SoHO/SUMER and IRIS.

Author:
Pavol Schwartz

Abstract:
A quiescent prominence was observed on 2013 October 22 at the NW limb in the lower-order Lyman lines of hydrogen up to Lyman-delta by SoHO/SUMER and in the MgII h&k near-UV lines by IRIS. Spectral profiles of these lines show often one or more intensity dips (reversals) between profile peaks due to self-absorption in line cores. The observations were targeted at the bright prominence core showing little dynamics. This part of the prominence is suitable for later non-LTE modeling assuming a quasi-static plasma with line-of-sight velocities causing Doppler shifts not exceeding widths of line profiles what is in case of the Lyman and MgII h&k lines few tens of km/s. In this contribution we show results of shape classification of line profiles and statistical analysis of their occurrence. Profiles are characterized by number of intensity peaks, integrated intensities, depths of central reversal, and asymmetry of peak intensities. An introduction of class of peculiar profiles, lacking prominent peaks, was also necessary. Results of the analysis are presented in the form of histograms. Such comprehensive and detailed statistical analysis, first of this kind ever, yields benchmark data for further non-LTE modeling of prominences. There is 30 % of 2-peak Lyman-alpha profiles with both peaks above the noise and if also profiles with more peaks with two of them above noise are added, this proportion rises up to half of all profiles observed in the analysed part of the prominence. On the other hand, for higher Lyman lines and MgII h&k lines there is much less of such profiles due to lower optical thickness in core of these lines. Thus, there is a question whether all peaks occurring in the observed profiles are real or they are just noise. Answer to this question will be given when analogous spectroscopic analysis is done to synthetic profiles obtained by the non-LTE modelling.