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Partial Redistribution Effects on Polarized Lines Formed in Moving Media in the Presence of a Weak Magnetic Field

Published online by Cambridge University Press:  24 July 2015

M. Sampoorna  and
K. N. Nagendra
M. Sampoorna
Affiliation:
Indian Institute of Astrophysics, Koramangala, Bengaluru 560 034, India email: sampoorna@iiap.res.in, knn@iiap.res.in
K. N. Nagendra
Affiliation:
Indian Institute of Astrophysics, Koramangala, Bengaluru 560 034, India email: sampoorna@iiap.res.in, knn@iiap.res.in
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Abstract

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Macroscopic velocity fields in stellar atmospheres significantly affect the shapes of the emergent Stokes profiles. The inextricable coupling between the angle and frequency variables becomes more complex in a moving medium when compared to a static medium. In this paper we consider both complete frequency redistribution (CRD) and partial frequency redistribution (PRD) in the line scattering of a two-level atom in the presence of an external weak magnetic field. For simplicity we consider empirical velocity laws to represent motion of the atmospheric layers. We present emergent Stokes profiles computed with CRD, angle-averaged PRD, and angle-dependent PRD. We show that angle-dependent PRD effects are important both in non-magnetic and magnetized scattering when vertical velocity gradients are present in the atmosphere. The results are presented for simple atmospheric models. They are expected to be of relevance to polarized line formation in slowly expanding chromospheric layers.

Keywords

Polarizationradiative transferscatteringstars: atmospheresSun: chromosphere
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 10 , Symposium S305: Polarimetry: From the Sun to Stars and Stellar Environments , December 2014 , pp. 387 - 394
Copyright
Copyright © International Astronomical Union 2015 

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