Comparison of gravity-induced and force-free magnetic dips
in quiescent prominences
S. Gunár, D.H. Mackay, P. Heinzel & U. Anzer
From the HINODE-6 meeting, Aug 14 – 17, 2012, St Andrews, UK
High-resolution observations of quiescent-prominence fine structures such as those obtained by Hinode/SOT show great variety of blob and thread-like small-scale features. Moreover, these fine structures exhibit a dynamical behaviour that represents a challenge for the understanding of quiescent prominences.
Despite a long-lasting modelling effort and a large number of superb observations of quiescent prominences, the nature of the magnetic field supporting prominences remains an open question. Today, two distinct modelling techniques are employed to describe the prominence fine structures. On one hand, large-scale prominence force-free magnetic field simulations and extrapolations can realistically represent their global magnetic structure and also positions of fine structures corresponding to the locations of dipped field lines. On the other hand, local multi-dimensional models of gravity-induced magnetic dips, usually of the Kippenhahn-Schlutter (KS) type, with realistic atmospheric models of prominence fine structures are able to produce the synthetic spectra in good agreement with observations and explain some dynamical aspects of quiescent prominences.
We present here the first comparison of local gravity-induced 2D KS-type magnetic dip models of prominence fine structures with fine structures located in the force-free dips produced by global 3D MHD simulations. In both cases we employ realistic models of the atmospheric structure including the prominence-corona transition region. We solve the 2D non-LTE radiative transfer problem for multi-level hydrogen atom and compare the hydrogen synthetic spectra of the gravity-induced and force-free models. We also discuss the validity of the force-free approximation for various values of the model parameters.
A combination of the gravity-induced and force-free prominence modelling holds a significant potential for a deeper understanding of quiescent prominences.