EDP Sciences
Free access
Issue
A&A
Volume 442, Number 1, October IV 2005
Page(s) 331 - 343
Section The Sun
DOI http://dx.doi.org/10.1051/0004-6361:20053360


A&A 442, 331-343 (2005)
DOI: 10.1051/0004-6361:20053360

Prominence fine structures in a magnetic equilibrium

II. A grid of two-dimensional models
P. Heinzel1, 2, U. Anzer2 and S. Gunár1, 3

1  Astronomical Institute, Academy of Sciences of the Czech Republic, 25165 Ondrejov, Czech Republic
    e-mail: [pheinzel;gunar]@asu.cas.cz
2  Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Strasse 1, 85740 Garching, Germany
    e-mail: ula@mpa-garching.mpg.de
3  Astronomical Institute, Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic

(Received 3 May 2005 / Accepted 1 July 2005 )

Abstract
We construct a grid of 2D vertical-thread models for prominence fine structures which are in magnetohydrostatic (MHS) equilibrium. Such thread models have been described in a previous paper by Heinzel & Anzer (2001), but here we use a modified 2D transfer code with an adaptive MHS grid. Multilevel non-LTE transfer calculations are now performed for a 12-level plus continuum hydrogen model atom, in order to study the behaviour of the Lyman-series lines observed by SOHO/SUMER. Our grid consists of 18 models which cover a range of central column masses, magnetic-field intensities and two parameters characterising the 2D temperature structure of the thread. Since different Lyman lines and their parts (line center, peak, wings) are formed at different places within the thread, the Lyman series may serve as a good diagnostic tool for thermodynamic conditions varying from central cool parts to a prominence-corona transition region. We demonstrate this behaviour for various lines, showing their synthetic profiles as seen from two perpendicular directions along and across the magnetic field lines, respectively, and displaying the respective contribution functions. This study confirms our earlier conclusion that the Lyman line profiles are much more reversed when seen across the field lines, compared to those seen along the lines. The latter can be even unreversed. We also show the geometrical cross-section (shape) of all 18 models. Their thread-like shape with a considerable aspect ratio resembles recent high-resolution H$\alpha$ images. Finally, we discuss the relation of our thread models to the vertical threads studied by Fontenla et al. (1996, ApJ, 466, 496).


Key words: Sun: prominences -- magnetohydrodynamics (MHD) -- radiative transfer -- line: profiles




© ESO 2005