Title: Non-LTE modelling of active filaments observed in the H_alpha 
line using the 2D flux-tube model


Authors: P. Schwartz, J. Koza, P. Heinzel, S. Gunár, H. Balthasar, 
C. Kuckein, J. Rybák, M. Verma, C. Denker, S.J. Gonzales Manrique, 
J. Jenkins, D. Long, P. Gömöry, A. Kučera


ABSTRACT:

We present development, current state and plans for future improvements
of our non-LTE 2D flux-tube model. The model is used for simulations of
spectroscopic observations in the H_alpha line of small-scale filaments 
in active
regions, arc filaments and filaments in state of activation. We assume that
filaments of these types are composed of flux-tubes located in the transi-
tion region and/or corona and relatively cool plasma can flow along these
flux-tubes with various velocities. The flux-tube system is approximated
in the model by a 2D horizontal slab where its finite dimensions form its
cross section and the infinite dimension is parallel to the solar 
surface. The
isothermal and isobaric slab is irradiated from the bottom and sides and the
non-LTE radiative transfer in the 2D geometry is solved using the MALI
numerical technique. The orientation of plasma flows in the slab is defined
by the azimuth and inclination angles. The influence of different plasma 
flow
velocities on the emerging radiation from the slab can be regulated using
filling factors. The model was already successfully applied to several fila-
ment Hα line spectroscopic observations made with the echelle spectrograph
at the Vacuum Tower Telescope (VTT) and the IBIS interferometer at the
Dunn Solar Telescope. In further development of the model we also plan to
introduce fine structures in 2D geometry composed of individual flux-tubes
and variation of the temperature and pressure within each flux-tube.