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Astron. Astrophys. 339, 286-297 (1998)

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Hydrogen line formation in dense magnetized plasmas

S. Brillant 1, 2, G. Mathys 1 and C. Stehlé 2

1 European Southern Observatory, Casilla 19001, Santiago 19, Chili
2 DARC et UPR 176 du CNRS, Observatoire Paris, 5 Place Jules Janssen, F-92190 Meudon, France

Received 9 January 1998 / Accepted 20 July 1998


The formation of hydrogen lines in dense plasmas in the presence of a uniform magnetic field is studied. The theory is developed for physical conditions (temperature, electronic density, magnetic field) characteristic of those encountered in the atmospheres of magnetic Ap and Bp stars. This is the first treatment of this problem dealing simultaneously with the Stark effect due to the electric microfields generated by the plasma ions and electrons, the Zeeman effect induced by the magnetic field, and the Stark effect that arises from the Lorentz electric field that the radiating atom is seeing as a result of its motion in the magnetic field. The contribution of the ions is calculated taking into account their dynamics. The Lorentz field introduces a coupling between the intrinsic line broadening and the Doppler effect due to the thermal motion, which in principle severely increases the complexity of the calculations. Special attention is paid to this aspect, and to the discussion of the conditions under which a simplified numerical treatment can be applied.

Key words: line: formation – line: profiles – plasmas – magnetic fields – radiative transfer – polarization

Send offprint requests to: C. Stehlé

© European Southern Observatory (ESO) 1998

Online publication: September 30, 1998