Astronomy and Astrophysics – Astrophysics
Scientific paper
Jun 1999
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999a%26a...346..322h&link_type=abstract
Astronomy and Astrophysics, v.346, p.322-328 (1999)
Astronomy and Astrophysics
Astrophysics
17
Line: Profiles, Radiative Transfer, Sun: Chromosphere, Sun: Filaments
Scientific paper
It was demonstrated in the previous paper (Paper I)that the cloud model technique can be largely improved if one considers realistic boundary conditions in evaluating the true form of the line source function. For structures seen against the solar disk, the Hα line source function is decreasing from bottom towards the top. In the present paper we investigate the effect of Doppler brightening on Hα source function. In frame of 1D non-LTE models it is demonstrated how the Hα line source function is increased depending on the velocity of the moving cloud and direction of the motion. For the same set of cloud models as used in Paper I, we have reevaluated the variations of the source function with optical depth including the effect of cloud motion. The resulting curves have been approximated by a second-degree polynomial and the respective coefficients have been subsequently used in a modified iterative method in order to derive the cloud model parameters. As expected, dynamical models lead to more precise specification of these parameters, namely the optical thickness, as compared to the static case investigated in Paper I. We have applied this new method to MSDP observations of a dark chromospheric feature (loop) with considerable flows.
Heinzel Petr
Mein Nicole
Mein Pierre
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