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Astron. Astrophys. 346, 322-328 (1999)


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Cloud model with variable source function for solar H[FORMULA] structures

II. Dynamical models

P. Heinzel 1, N. Mein 2 and P. Mein 2

1 Astronomical Institute, Academy of Sciences of the Czech Republic, CZ-25165 Ondejov, Czech Republic
2 Observatoire de Paris, Section de Meudon, F-92195 Meudon Principal Cedex, France

Received 19 November 1997 / Accepted 25 February 1999

Abstract

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 H[FORMULA] line source function is decreasing from bottom towards the top. In the present paper we investigate the effect of Doppler brightening on H[FORMULA] source function. In frame of 1D non-LTE models it is demonstrated how the H[FORMULA] 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.

Key words: line: profiles – radiative transfer – Sun: chromosphere – Sun: filaments

Send offprint requests to: pheinzel@asu.cas.cz

© European Southern Observatory (ESO) 1999

Online publication: May 6, 1999

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