NLTE diagnostics of a filament observed by SOHO/SUMER in hydrogen Lyman line series

We present the NLTE diagnostics of a filament observed by SOHO/SUMER on May 27, 2005 in the whole Lyman series. The filament was situated at the disk center. The L_alpha observations were carried out with a normal voltage of the detector A and the line was placed at the central part of the detector - outside the L_alpha attenuator. Therefore, the observed profiles of this line could be calibrated reliably. The core of this line is much more sensitive to the absorption in cool hydrogen plasma of the filament than higher Lyman lines. Therefore the results of the diagnostics using profiles of the whole Lyman series plus Lyman continuum are more reliable than the results obtained from our previous work where filaments were observed only in L_beta and higher Lyman lines. In our NLTE model used for computations of the synthetic profiles the filament is approximated by a one-dimensional isobaric slab with two analogous prominence-corona transition regions - one at the bottom and another on the top of the slab. Observed profiles are fitted by synthetic ones using the methods developed in our previous work. Results of the diagnostics are the properties of the filament plasma such as the temperatures, gas pressure, plasma densities, ionization degree, etc. We also study the effect of 2D radiative transfer on the Lyman profiles emergent from solar filaments.