Dynamics of quiescent prominence fine structures analyzed
by 2D non-LTE modelling of the Hα line
S. Gunár, P.Mein, B. Schmieder, P. Heinzel & N.Mein
Aims: We analyze the dynamics of the prominence fine structures of a quiescent prominence observed on April 26, 2007 during a coordinated campaign of several spaceborne and ground-based instruments. We use Lyman spectra observed by SOHO/SUMER and the Hα line spectra obtained by MSDP spectrograph working at the Meudon Solar Tower.
Methods: We employ the 2D multi-thread prominence fine-structure modelling that includes randomly distributed line-of-sight (LOS) velocities of individual threads to derive models producing synthetic Lyman lines in good agreement with the SOHO/SUMER observations. We then use these models to produce synthetic Hα line spectra that we compare with the observed spectra using three statistical parameters: the line integrated intensity, the line full-width at half-maximum (FWHM), and the Doppler velocity derived
from shifts of the line profiles.
Results: We demonstrate that the 2D multi-thread models that produce synthetic Lyman spectra in agreement with observations also generate synthetic Hα spectra in good agreement with the observed ones. The statistical analysis of the FWHMand Doppler velocities of the synthetic Hα line profiles show that the overall LOS velocities in the April 26, 2007 prominence at the time of the observations were below 15 km/s and in the prominence core were close to 10 km/s. In combination with the analysis of the Lyman spectra, we determine several physical parameters of the observed prominence fine-structures that show that the April 26, 2007 prominence had a relatively low-mass weakly magnetized structure.We are also able to impose some constraints on the prominence core temperature, which may be relatively low, with values below 6000 K.
Conclusions: The combination of 2D non-LTE prominence fine-structure modelling with the statistical analysis of the observed and synthetic Lyman and Hα spectra allows us to analyze the influence of the model input parameters and the velocity fields on the synthetic Hα line profiles, thus determine the overall dynamics of the observed prominence as well as the physical parameters of its plasma.